JP2012130061A - Impedance matching device and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impedance matching device that enables lossless transmission of a power input from a transmission side to a reception side.SOLUTION: The impedance matching device determines a control value corresponding to a direction to increase a coupling coefficient from a control value for a matched state if determining that a coupling between a transmission antenna and a reception antenna is shifted in a stronger direction from the matched state of coupling, and determines a control value corresponding to a direction to decrease the coupling coefficient from the control value for the matched state if determining that the coupling between the transmission antenna and the reception antenna is shifted in a weakening direction from the matched state of coupling.

Description

  The present invention relates to a wireless contactless power transmission system, and more particularly to an impedance matching device useful for a wireless power transmission system based on the principle of electromagnetic resonance coupling (also referred to as magnetic field resonance or electric field resonance).

  2. Description of the Related Art In recent years, wireless non-contact power transmission technology that does not require connection of an AC (Alternating Current) cable or the like has begun to be used when supplying power to home appliances, industrial devices, electric vehicles, and the like. In homes, non-contact charging devices are widely used for small devices around water such as electric toothbrushes and shavers, and portable devices such as mobile phones. For electric vehicles, a system for charging or supplying electric power in a non-contact manner from an electric power supply device placed under the vehicle body has been put into practical use for an electric vehicle stopped at a parking lot or a bus stop.

  There are three main types of power transmission technologies using radio waves (electromagnetic waves). They are an electromagnetic induction method, an electromagnetic resonance coupling method, and a microwave power transmission method. Among them, the electromagnetic induction method is widely used for the above-mentioned household use, industrial use, and electric vehicle, and has been widely commercialized from a low power of several W to a high power of several tens kW. However, the electromagnetic induction method requires that the distance between the power transmission side coil (primary side coil) and the reception side coil (secondary side coil) (air gap, hereinafter referred to as “gap”) be as small as possible. And it is a big subject to be weak against the positional deviation between the transmitting and receiving coils, and the applicable area is limited. In addition, as a system that employs a microwave power transmission system, SPS (Solar Power) transmits power generated by a solar panel attached to an artificial satellite to a receiving antenna on the ground using radio waves with a very narrow beam width. Satelite) system has been studied, but it requires a fairly large facility. For electric vehicles, trial production has been reported in which a waveguide slot antenna is used in the transmission section and a patch antenna and rectifier are combined in the reception section, but the current problem is that efficiency is low.

  Under such circumstances, wireless power transmission by the electromagnetic resonance coupling method has been attracting attention in recent years (see, for example, Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1). This method is characterized by a large gap between the transmitting and receiving antennas (several tens of centimeters to several meters) and resistance to misalignment, and it can be applied in a wide range of applications such as household equipment, industrial equipment, and electric vehicles. Expected. The electromagnetic resonance coupling method is also highly expected to supply power wirelessly to a moving body as an area impossible by electromagnetic induction.

Special table 2009-501510 Japanese Patent No. 4225953

A. Kurs, A. Karalis, et al. “Wireless Power Transfer via Strongly Coupled Magnetic Resonances”, Science, Vol. 317,6 July 2007 Imura, Hori, “Transmission technology by electromagnetic resonance coupling”, IEEE Journal, Vol. 129, Vo. 7, 2009 Here, the electromagnetic resonance coupling method will be described. FIG. 32 is a block diagram of an example of a wireless power transmission system according to the electromagnetic resonance coupling method. The transmission unit connects a transmission side circuit unit including a transmission signal source that generates a radio frequency high-frequency signal, an amplification unit that amplifies the signal to a signal level of transmission power, and the transmission side circuit unit and the transmission antenna. A cable unit and a transmission antenna that radiates a wireless power signal are provided. The reception unit includes a reception antenna that receives a wireless power signal radiated from the transmission antenna, a rectifier circuit that rectifies the received high-frequency signal, and a load device that consumes the received power. The transmitting antenna and the receiving antenna have the same resonance frequency and are generally installed facing each other. The wireless power transmission system shown in FIG. 32 generates a magnetic field or an electric field in the near field of the transmitting antenna by driving the transmitting antenna with a high-frequency signal equal to the resonance frequency, and resonates the receiving antenna placed in the near field. To transmit power.

  In the above-mentioned documents and the like, the electromagnetic resonance coupling method has a technical advantage that it can take a larger gap than the electromagnetic induction method and is resistant to displacement. On the other hand, the electromagnetic resonance coupling method has a characteristic that when the gap between the transmitting and receiving antennas changes, the transmission efficiency changes greatly accordingly. However, since it is desired that the transmission efficiency is as close to 100% as possible in all aspects aimed at power transmission, such characteristics are not preferable.

  Also, considering the case where the electromagnetic resonance coupling method is applied as a power feeding means to a moving automobile, light rail vehicle, bicycle, etc., in such a moving body, the continuous fluctuation of the gap between the transmitting antenna and the receiving antenna Or a constant misalignment condition occurs. Even in such a situation, it is desired to supply power in a state as stable as possible.

  The present invention has been made in order to solve the above-described problems. The transmission efficiency is achieved by following the impedance matching state at a high speed with respect to fluctuations of the coupling state between the transmitting antenna and the receiving antenna with time. An object of the present invention is to provide an impedance matching device capable of maintaining a high level of the impedance.

According to one aspect of the present invention, in the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, is disposed between the transmitting antenna and the transmission circuit, and the impedance of the transmission circuit, the impedance of the transmitting antenna When, an impedance matching device shall be the matching state, connected with a variable inductor element is inserted in series between the transmitting antenna and the transmitting circuit, in parallel with the transmitting antenna side of the variable inductor element And a control value corresponding to an inductance value and a capacitance value necessary for matching with a predetermined impedance value using the matching circuit of the first type , a first storage unit having stored in advance in correspondence with the coupling coefficient between the transmitting antenna and the receiving antenna, A second type matching circuit comprising: a variable inductor element inserted in series between the transmitter circuit and the transmitter antenna; and a variable capacitor element connected in parallel to the transmitter circuit side relative to the variable inductor element. When the inductance value required to match the predetermined impedance value with the matching circuit of the second type and the control value corresponding to the capacity stance value, corresponding to the coupling coefficient between the transmit and receive antennas When it is determined that the second storage unit stored in advance and the coupling between the transmission antenna and the reception antenna are shifted in a direction that is stronger than the coupling in the matching state, the control in the matching state is performed. A control value corresponding to a direction in which the coupling coefficient increases from the value, and the coupling between the transmitting antenna and the receiving antenna is the matching state That when it is determined that the shift in the weaker direction than binding, the control value determining unit for determining a control value corresponding to the direction in which the coupling coefficient is reduced from the control value in the matching condition, the control value determination reads the control value part is determined, characterized in that it comprises a control value output unit to be reflected in the matching circuit of the first type or the second type.

Invention according to claim 6, in the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, is disposed between the transmitting antenna and the transmission circuit, and the impedance of the transmission circuit, the impedance of the transmitting antenna When, an impedance matching device shall be the matching state, connected with a variable inductor element is inserted in series between the transmitting antenna and the transmitting circuit, in parallel with the transmitting antenna side of the variable inductor element And a control value corresponding to an inductance value and a capacitance value necessary for matching with a predetermined impedance value using the matching circuit of the first type , a first storage unit having stored in advance in correspondence with the coupling coefficient between the transmitting antenna and the receiving antenna, A second type matching circuit comprising: a variable inductor element inserted in series between the transmitter circuit and the transmitter antenna; and a variable capacitor element connected in parallel to the transmitter circuit side relative to the variable inductor element. When the inductance value required to match the predetermined impedance value with the matching circuit of the second type and the control value corresponding to the capacity stance value, corresponding to the coupling coefficient between the transmit and receive antennas A control method executed by an impedance matching device including a second storage unit stored in advance, wherein a coupling between the transmission antenna and the reception antenna is shifted in a direction in which the coupling is stronger than a coupling in the matching state. A control value corresponding to the direction in which the coupling coefficient increases is determined from the control value in the matching state, When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that becomes weaker than the coupling that is in the matching state, the coupling coefficient is reduced from the control value in the matching state. wherein the control value determining step of determining a control value, reads the control value by the control value determining step has determined, that and a control value output step to be reflected in the matching circuit of the first type or the second type And

Invention according to claim 7, in the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, is disposed between the transmitting antenna and the transmission circuit, and the impedance of the transmission circuit, the impedance of the transmitting antenna When, an impedance matching device shall be the matching state, connected with a variable inductor element is inserted in series between the transmitting antenna and the transmitting circuit, in parallel with the transmitting antenna side of the variable inductor element a matching circuit including a variable capacitor element, a being, a control value corresponding to the inductance values and capacitance values required to match the predetermined impedance value using the matching circuit, and the transmit and receive antennas a storage unit having stored in advance in correspondence with the coupling coefficient, the receiving and the transmitting antenna When it is determined that the coupling between the antennas is shifted in a direction that becomes stronger than the coupling that is in the aligned state, a control value corresponding to the direction in which the coupling coefficient is increased is determined from the control value in the aligned state. When it is determined that the coupling between the transmission antenna and the reception antenna is shifted in a direction in which the coupling is weaker than the coupling in the matching state, the coupling coefficient is decreased from the control value in the matching state. a control value determining unit for determining a corresponding control value, reads the control value by the control value determining unit has determined, characterized in that it comprises a control value output unit to be reflected in the matching circuit.

Invention according to claim 8, in the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, is disposed between the transmitting antenna and the transmission circuit, and the impedance of the transmission circuit, the impedance of the transmitting antenna When, an impedance matching device shall be the matching state, connected with a variable inductor element is inserted in series between the transmitting antenna and the transmitting circuit, in parallel to the transmitting circuit side of the variable inductor element a matching circuit including a variable capacitor element, a being, a control value corresponding to the inductance values and capacitance values required to match the predetermined impedance value using the matching circuit, and the transmit and receive antennas a storage unit having stored in advance in correspondence with the coupling coefficient, the receiving-en and the transmitting antenna When it is determined that the coupling between the two is shifted in a direction that becomes stronger than the coupling that is in the matching state, a control value corresponding to the direction in which the coupling coefficient is increased is determined from the control value in the matching state. When it is determined that the coupling between the transmission antenna and the reception antenna is shifted in a direction in which the coupling is weaker than the coupling in the matching state, the coupling coefficient is decreased from the control value in the matching state. a control value determining unit for determining a corresponding control value, reads the control value by the control value determining unit has determined, and having a control value output unit to be reflected in the matching circuit.

  In one aspect of the impedance matching device of the present invention, the impedance matching device obtains a control value for the matching circuit based on the input impedance change trajectory peculiar to the electromagnetic resonance coupling method, and stores it in the storage unit. The impedance matching device can quickly move by moving an appropriate amount in an appropriate direction in a table of a storage unit prepared in advance even when the alignment is once again after being matched. The consistency state can be recovered. This is because the input impedance to be matched after the matching is shifted still exists on the locus of the input impedance change. As a result, the impedance matching device can quickly follow an impedance change accompanying a continuous change in the coupling state between transmission and reception, such as when moving.

  Further, the impedance matching device proceeds when the matching is deviated and the reflected power becomes large and it is determined that the matching needs to be adjusted, that is, when the absolute value of the reflection coefficient exceeds a predetermined threshold. The control value of the matching circuit may be updated in the direction of increasing the impedance value in the table of the storage unit or updated in the decreasing direction by a simple calculation result of phase comparison between the wave voltage and the reflected wave voltage. Judge what to do. Therefore, in this impedance matching device, the circuit of this part is easily manufactured. In one aspect of the impedance matching device, when the impedance matching device performs readjustment of matching, the control value of the matching circuit is set in the table according to the reflection coefficient absolute value equivalent value corresponding to the deviation amount of the impedance value. Since the adjustment step width at the time of reading can be changed, when the amount of deviation is large, it is possible to increase the speed of matching state tracking by increasing the adjustment step width.

  In addition, the impedance matching device obtains a control value for the matching circuit based on the locus of input impedance change peculiar to the electromagnetic resonance coupling method, and stores the control value in the storage unit, so that the conventional general impedance matching circuit can be obtained. In comparison, the memory size required for the storage unit can be greatly reduced. In addition, these control values are quantized so that the power loss due to reflection is always less than or equal to a predetermined threshold value, so that it is possible to further reduce the required memory size while suppressing the increase in loss due to reflection. It is.

1 shows a schematic configuration diagram of a transmission system according to a first embodiment. FIG. An example of the antenna used as a transmitting antenna and a receiving antenna is shown. The result of having analyzed the input impedance of a transmission / reception antenna with the three-dimensional electromagnetic field analysis simulator is shown. It is an example of the serial-parallel type equivalent circuit of a transmission / reception antenna. 5 is a graph plotting both the result of the equivalent circuit analysis of FIG. 4 and the result of the electromagnetic field analysis of FIG. The positional relationship between the transmitting antenna and the receiving antenna during power transmission is shown. FIG. 7 is a diagram representing the system shown in FIG. 6 by a series-parallel equivalent circuit. It is the figure which calculated | required the locus | trajectory of the input impedance when changing a coupling coefficient, and plotted it on the Smith chart. It is the figure which calculated | required the locus | trajectory of the input impedance when changing a coupling coefficient, and plotted it on the Smith chart. A result obtained by modeling a transmission / reception antenna using a series-parallel equivalent circuit, and measuring a traveling wave voltage waveform Vf and a reflected wave voltage waveform Vr by inserting a directional coupler between the transmission circuit 1 and the transmission antenna 4 is shown. It is a structural example of the matching circuit of a 1st format and a 2nd format. In the schematic diagram, an arbitrary point on the input impedance locus is moved along the iso-resistance circle and the iso-conductance circle on the Smith chart using the first or second type matching circuit to reach the matching point of 50Ω. is there. It is the figure which showed typically the preparation method of the table memorize | stored as a 1st memory | storage part. It is an example of the map corresponded to a 1st memory | storage part. It is the figure which showed typically the preparation method of the table memorize | stored as a 2nd memory | storage part. It is an example of the map corresponded to a 2nd memory | storage part. It is an example of the graph which shows the control value before and behind quantization memorize | stored in a 1st memory | storage part. It is an example of the table corresponded to a 1st memory | storage part. It is an example of the graph which shows the control value before and behind quantization memorize | stored in a 2nd memory | storage part. It is an example of the table corresponded to a 2nd memory | storage part. It is an example of the graph which shows a traveling wave voltage and the reflected wave voltage corresponding to each coupling coefficient. It is an example of the graph which shows a traveling wave voltage and the reflected wave voltage corresponding to each coupling coefficient. It is a graph which shows a traveling wave voltage and a reflected wave voltage, and a graph which shows transmission efficiency. It is a graph which shows a traveling wave voltage and a reflected wave voltage, and a graph which shows transmission efficiency. It is a graph which shows a traveling wave voltage and a reflected wave voltage, and a graph which shows transmission efficiency. It is a graph which shows a traveling wave voltage and a reflected wave voltage, and a graph which shows transmission efficiency. It is a graph which shows a traveling wave voltage and a reflected wave voltage, and a graph which shows transmission efficiency. It is a graph which shows a traveling wave voltage and a reflected wave voltage, and a graph which shows transmission efficiency. It is an example of the flowchart which shows the process sequence of a 1st impedance matching. It is an example of the flowchart which shows the process sequence of a 2nd impedance matching. The schematic block diagram of the transmission system which concerns on 2nd Embodiment is shown. An example of the block diagram of the wireless power transmission system according to an electromagnetic resonance coupling system is shown. The modification of a matching circuit is shown. Fig. 5 illustrates a transmission system for matching mismatches in the direction of closer gaps. Fig. 5 illustrates a transmission system for matching mismatches in the direction of increasing gaps.

  One aspect of the present invention is an impedance matching device installed between a transmission circuit and a transmission antenna in a wireless power transmission system conforming to an electromagnetic resonance coupling method, which corresponds to a transmission signal from the transmission circuit. An absolute value of the reflection coefficient based on the traveling wave voltage and the reflected wave voltage, and the traveling wave voltage and reflected wave voltage extraction unit for extracting the traveling wave voltage and the reflected wave voltage corresponding to the reflected signal from the transmitting antenna. Alternatively, a reflection coefficient calculation unit that calculates a reflection coefficient absolute value equivalent value that is a value corresponding to the absolute value is compared with the phase of the traveling wave voltage and the phase of the reflected wave voltage, and a delay or advance between the phases. A phase determination unit that performs phase determination, a variable inductor element inserted in series between the transmission circuit and the transmission antenna, and the transmission antenna side of the variable inductor element A matching circuit of a first type comprising variable capacitor elements connected in parallel, and a control corresponding to an inductance value and a capacitance value necessary for matching to a predetermined impedance value using the matching circuit of the first type A first storage unit stored in advance in association with a value corresponding to an absolute value of a reflection coefficient according to the order of the coupling coefficient between the corresponding transmission antenna and reception antenna, the transmission circuit, and the transmission antenna. A second-type matching circuit comprising: a variable inductor element inserted in series between the first and second variable inductor elements; and a variable capacitor element connected in parallel to the transmitter circuit side of the variable inductor element; The control value required to match a predetermined impedance value using a circuit is set to a large coupling coefficient between the corresponding transmitting antenna and receiving antenna. In accordance with the order of the reflection coefficient absolute value equivalent value, the second storage unit stored in advance and the first-type matching circuit, the second-type matching circuit, or a through circuit in which no matching circuit is inserted, When the control value is read from the first or second storage unit based on the phase determination and the switch unit that electrically connects any of the transmission circuit and the transmission antenna, Direction of control value reading position for selecting a control value corresponding to a case where the coupling coefficient increases from a control value currently used or a control value corresponding to a case where the coupling coefficient decreases Selection of the first-type or second-type matching circuit or a through circuit that does not insert a matching circuit based on the adjustment direction determining unit that determines the reading position, the direction of the reading position, and the step width for changing the reading position The second Selection of the first or second storage unit to be used when the matching circuit of one format or the second format is selected, and a reading position determining unit that determines the reading position, and the reading position determining unit selects Matching that operates the switch unit so that either the matching circuit of the first type or the second type or the through circuit that does not insert the matching circuit is electrically connected between the transmission circuit and the transmission antenna. A circuit selection unit; a storage unit selection unit that selects the first or second storage unit selected by the readout position determination unit as a storage unit that reads the control value; and the first unit selected by the storage unit selection unit. A control value corresponding to the read position determined by the read position determination unit is read from the first or second storage unit and reflected in the matching circuit of the first format or the second format selected by the matching circuit selection unit. And a control value output unit that, the.

  The impedance matching device is installed between a transmission circuit and a transmission antenna in a wireless power transmission system in accordance with an electromagnetic resonance coupling method. The impedance matching device includes a traveling wave / reflected wave extraction unit, a reflection coefficient calculation unit, a phase determination unit, a first type matching circuit, a first storage unit, a second type matching circuit, a second type A storage unit, a switch unit, an adjustment direction determination unit, a reading position determination unit, a matching circuit selection unit, a storage unit selection unit, and a control value output unit. The first storage unit uses a first-type matching circuit to match control values corresponding to inductance values and capacitance values necessary for matching to a predetermined impedance value, as a coupling coefficient between the corresponding transmission antenna and reception antenna. In accordance with the order of magnitude, it is stored in advance in association with the reflection coefficient absolute value equivalent value. Here, the “control value” means an inductance value and a capacitance value, a control voltage value for changing the inductance value and the capacitance value using an electrical or mechanical mechanism such as a motor, a plurality of minute inductor elements, For example, a bit pattern for controlling ON / OFF of a switch unit such as a relay or a MEMS (Micro Electro Mechanical System) included in an LC network circuit composed of minute capacitor elements is applicable. In addition, “the coupling coefficient between the corresponding transmission antenna and the receiving antenna” refers to a coupling coefficient suitable when each control value is reflected in the first-type matching circuit, and “in order of the coupling coefficient”. “Stored” indicates that the control values are stored in the descending order of the coupling coefficient corresponding to each control value. Similarly, the second storage unit sets the control values necessary for matching to a predetermined impedance value using the second type matching circuit according to the order of the coupling coefficient between the corresponding transmission antenna and reception antenna. , And stored in advance in association with the reflection coefficient absolute value equivalent value. The reflection coefficient calculation unit calculates a reflection coefficient absolute value equivalent value based on the traveling wave voltage and the reflected wave voltage extracted by the traveling wave / reflected wave extraction unit. Here, the “reflection coefficient absolute value equivalent value” is a value corresponding to the absolute value of the reflection coefficient, such as an absolute value of the reflection coefficient or a value uniquely related to the reflection coefficient. This applies to the absolute value of impedance. The phase determination unit compares the phase of the traveling wave voltage with the phase of the reflected wave voltage, and determines a delay or advance between the phases. Based on the phase determination, the adjustment direction determination unit selects a control value corresponding to a case where the coupling coefficient becomes larger than the currently used control value when reading the control value from the first or second storage unit Whether to select a control value corresponding to a case where the coupling coefficient is small or to determine a control value reading position is determined. "Direction of control value readout position" is newly applied when each control value is stored in order of increasing or decreasing coupling coefficient and the current control value is stored as a reference. The direction to the position where the control value to be stored is stored. The reading position determination unit selects a first type or second type matching circuit or a through circuit that does not insert a matching circuit based on the direction of the reading position and the step width for changing the reading position, the first type or the second type. When the two types of matching circuits are selected, the first or second storage unit to be used is selected and the reading position is determined. “Step width” refers to a width based on the number of control values based on the current control value when the control values are stored in order of increasing or decreasing coupling coefficient. This step width may be an invariant value or a variable value. The matching circuit selection unit is electrically connected between the transmission circuit and the transmission antenna, either the first type or the second type matching circuit selected by the reading position determination unit or a through circuit that does not insert the matching circuit. The switch part is operated so that A memory | storage part selection part selects the 1st or 2nd memory | storage part which the reading position determination part selected as a memory | storage part which reads a control value. The control value output unit reads the control value corresponding to the reading position determined by the reading position determination unit from the first or second storage unit selected by the storage unit selection unit, and the first selected by the matching circuit selection unit It is reflected in the matching circuit of the type or the second type. In this way, the impedance matching device keeps the transmission efficiency high by tracking the impedance matching state at a high speed with respect to the fluctuation of the coupling state of the transmitting antenna and the receiving antenna with time. Can do.

  In one aspect of the impedance matching device, the adjustment step width determination unit that determines whether or not the control value currently used is adjusted based on the reflection coefficient absolute value equivalent value and the step width is further included. Prepare. As a result, the impedance matching device can flexibly change the step width and increase the speed of tracking the matching state even when the coupling state between the transmitting antenna and the receiving antenna changes drastically.

  In another aspect of the impedance matching apparatus, the control value is obtained when the transmission antenna and the reception antenna of the electromagnetic resonance coupling method are opposed to each other and the gap between the transmission antenna and the reception antenna is changed. It is set based on the locus of change in input impedance from the circuit to the transmitting antenna. The impedance matching device stores the control value set in this way in advance and performs impedance matching, thereby reducing processing steps and reducing the circuit scale and the required memory capacity.

  In another aspect of the above impedance matching device, the control value is generated by quantization so that the loss due to reflection is always equal to or less than a predetermined threshold value. By performing impedance matching based on the control value, the impedance matching device can always reduce the loss due to reflection after matching to a predetermined threshold value or less.

  In another aspect of the impedance matching apparatus, the control value is such that the quantization interval decreases as the absolute value of the reflection coefficient or a reflection coefficient absolute value equivalent value that is a value corresponding to the absolute value increases. Quantized to The impedance matching device performs impedance matching based on the control value, so that the loss due to reflection after matching can be made to be equal to or less than a predetermined threshold.

  In another aspect of the present invention, in a wireless power transmission system according to an electromagnetic resonance coupling method, the wireless power transmission system is installed between a transmission circuit and a transmission antenna, and is inserted in series between the transmission circuit and the transmission antenna. A first-type matching circuit comprising: a variable inductor element; and a variable capacitor element connected in parallel to the transmitting antenna side with respect to the variable inductor element; and a predetermined impedance value using the first-type matching circuit Control values corresponding to the inductance value and the capacitance value necessary for matching with each other are stored in advance in association with the corresponding value of the reflection coefficient absolute value according to the order of the coupling coefficient between the corresponding transmitting antenna and receiving antenna. A first storage unit, a variable inductor element inserted in series between the transmission circuit and the transmission antenna, and the variable inductor A variable capacitor element connected in parallel to the transmitter circuit side of the element, and a matching circuit of a second type provided with a matching circuit of the second type necessary for matching to a predetermined impedance value using the matching circuit of the second type A second storage unit that stores the control value in advance in association with the corresponding reflection coefficient absolute value according to the order of the coupling coefficient between the transmitting antenna and the receiving antenna, and the matching circuit of the first type An impedance matching device comprising: a switch unit that electrically connects either the matching circuit of the second type or a through circuit in which no matching circuit is inserted between the transmitting circuit and the transmitting antenna A traveling wave / reverse signal for extracting a traveling wave voltage corresponding to a transmission signal from the transmission circuit and a reflected wave voltage corresponding to a reflected signal from the transmission antenna. A reflection coefficient calculating step of calculating a reflection coefficient absolute value or a reflection coefficient absolute value equivalent value that is a value corresponding to the absolute value based on the traveling wave voltage and the reflected wave voltage; A phase determination step for comparing the phase of the wave voltage with the phase of the reflected wave voltage and determining a delay or advance between the phases, and the first or second storage unit based on the phase determination When the control value is read from the control value, the control value corresponding to the case where the coupling coefficient increases from the currently used control value is selected, or the control value corresponding to the case where the coupling coefficient becomes small is selected. A matching circuit of the first type or the second type based on an adjustment direction determining step for determining the direction of the read position of the control value to be determined, the direction of the read position, and the step width for changing the read position Or matching circuit A read position determining step for selecting a through circuit without inserting a signal, selecting the first or second storage unit to be used when the first or second type matching circuit is selected, and determining the read position And the first type or second type matching circuit selected by the reading position determination step or a through circuit not including a matching circuit is electrically connected between the transmission circuit and the transmission antenna. A matching circuit selection step for operating the switch unit, a storage unit selection step for selecting the first or second storage unit selected by the read position determination step as a storage unit for reading the control value, A control value corresponding to the read position determined by the read position determining step is read from the first or second storage unit selected by the storage unit selecting step, and the matching circuit selecting step is selected. Provided to the control value output step to be reflected in the matching circuit of the first type or the second type has a. By executing this control method, the impedance matching device keeps the transmission efficiency at a high level by following the impedance matching state at a high speed with respect to fluctuations in the coupling state between the transmitting antenna and the receiving antenna over time. You can continue.

  In another aspect of the present invention, in a wireless power transmission system conforming to an electromagnetic resonance coupling method, an impedance matching device installed between a transmission circuit and a transmission antenna, and corresponding to a transmission signal from the transmission circuit An absolute value of the reflection coefficient based on the traveling wave voltage and the reflected wave voltage, and the traveling wave voltage and reflected wave voltage extraction unit for extracting the traveling wave voltage and the reflected wave voltage corresponding to the reflected signal from the transmitting antenna. Alternatively, a reflection coefficient calculation unit that calculates a reflection coefficient absolute value equivalent value that is a value corresponding to the absolute value is compared with the phase of the traveling wave voltage and the phase of the reflected wave voltage, and a delay or advance between the phases. A phase determination unit that performs phase determination, a variable inductor element inserted in series between the transmission circuit and the transmission antenna, and closer to the transmission antenna than the variable inductor element A matching circuit comprising: a variable capacitor element connected to the column; and a control value corresponding to an inductance value and a capacitance value necessary for matching with a predetermined impedance value using the matching circuit, the corresponding transmitting antenna In accordance with the order of the coupling coefficient between the receiving antenna and the receiving antenna, in association with the reflection coefficient absolute value equivalent value, any one of the storage unit stored in advance and the matching circuit or the through circuit in which no matching circuit is inserted, A switch unit electrically connected between the transmission circuit and the transmission antenna; a matching circuit selection unit that operates the switch unit based on the reflection coefficient absolute value equivalent value; and the storage unit based on the phase determination When the control value is read from the control value, the control value corresponding to the case where the coupling coefficient increases from the currently used control value is selected, or the previous An adjustment direction determining unit that determines a direction of a reading position of a control value to select a control value corresponding to a case where a coupling coefficient is small, a direction of the reading position, and a step width for changing the reading position A read position determination unit that determines the read position, a control value output unit that reads a control value corresponding to the read position determined by the read position determination unit from the storage unit, and reflects the control value to the matching circuit; . By doing so, the impedance matching device matches the impedance matching state with respect to fluctuations of the coupling state of the transmitting antenna and the receiving antenna over time when matching the mismatch corresponding to the direction in which the gap is closer. It is possible to keep the transmission efficiency in a high state by following the signal at a high speed.

  In another aspect of the present invention, in a wireless power transmission system conforming to an electromagnetic resonance coupling method, an impedance matching device installed between a transmission circuit and a transmission antenna, and corresponding to a transmission signal from the transmission circuit An absolute value of the reflection coefficient based on the traveling wave voltage and the reflected wave voltage, and the traveling wave voltage and reflected wave voltage extraction unit for extracting the traveling wave voltage and the reflected wave voltage corresponding to the reflected signal from the transmitting antenna. Alternatively, a reflection coefficient calculation unit that calculates a reflection coefficient absolute value equivalent value that is a value corresponding to the absolute value is compared with the phase of the traveling wave voltage and the phase of the reflected wave voltage, and a delay or advance between the phases. A phase determination unit for performing phase determination, a variable inductor element inserted in series between the transmission circuit and the transmission antenna, and in parallel to the transmission circuit side with respect to the variable inductor element A matching circuit comprising: a variable capacitor element connected; and a control value corresponding to an inductance value and a capacitance value necessary for matching with a predetermined impedance value using the matching circuit, the corresponding transmitting antenna and receiving According to the order of the coupling coefficient with the antenna, in association with the reflection coefficient absolute value equivalent value, any one of the storage unit stored in advance and the matching circuit or the through circuit in which no matching circuit is inserted is used as the transmission circuit. A switch unit that is electrically connected to the transmission antenna, a matching circuit selection unit that operates the switch unit based on the reflection coefficient absolute value equivalent value, and a phase determination based on the phase determination. When reading the control value, select a control value corresponding to the case where the coupling coefficient is larger than the currently used control value, or Based on the adjustment direction determination unit that determines the direction of the reading position of the control value to select the control value corresponding to the case where the coefficient becomes small, the direction of the reading position, and the step width for changing the reading position A read position determination unit that determines the read position; a control value output unit that reads from the storage unit a control value corresponding to the read position determined by the read position determination unit, and reflects the control value to the matching circuit; Is provided. In this way, the impedance matching device can match the impedance matching state against fluctuations over time of the coupling state of the transmitting antenna and the receiving antenna when matching the mismatch corresponding to the direction in which the gap is far away. It is possible to keep the transmission efficiency in a high state by following the signal at a high speed.

  In one aspect of the impedance matching device, the adjustment step width determination unit that determines whether or not the control value currently used is adjusted based on the reflection coefficient absolute value equivalent value and the step width is further included. Prepare.

  In another aspect of the impedance matching apparatus, the control value is obtained when the transmission antenna and the reception antenna of the electromagnetic resonance coupling method are opposed to each other and the gap between the transmission antenna and the reception antenna is changed. It is set based on the locus of change in input impedance from the circuit to the transmitting antenna.

  In addition, although described as a through circuit in which a matching circuit is not inserted as one of the circuits to be switched in the switch unit, the mounting method having the same effect as a through state in which a matching circuit is not inserted is essential. Any implementation method is acceptable. For example, an implementation method that does not have a circuit path that explicitly passes through the matching circuit, but is equivalent to a state in which the matching circuit is not included by setting the value of the variable inductance to zero is also used for the matching circuit. This is considered the same as switching to a through circuit that is not inserted.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
[Overview]
FIG. 1 is a schematic configuration diagram of a transmission system 100 according to the first embodiment. As shown in FIG. 1, the transmission system 100 includes a transmission circuit 1, an impedance matching device 2, and a transmission antenna 4. Hereinafter, the “initial state” refers to a state where the transmission system 100 is not impedance matched. The “gap Gp” refers to a gap between the transmission antenna and the reception antenna.

  The transmission circuit 1 includes a transmission signal source 11 and an amplification unit 12. The transmission signal source 11 generates a high frequency signal used for wireless power transmission. The amplification unit 12 functions as a control circuit such as a start operation and a stop operation when transmitting power while adjusting the magnitude of the power to be transmitted.

  As will be described later, when the transmission system 100 is in an initial state, the impedance matching device 2 performs impedance matching so that the transmission system 100 is matched with a predetermined impedance value (also referred to as “matching state”). Do. Hereinafter, the impedance matching in this case is also referred to as “first impedance matching”. The impedance matching device 2 performs impedance matching even when the impedance value deviates from the matching state again due to a change in the gap Gp after the first impedance matching. Hereinafter, the impedance matching in this case is also referred to as “second impedance matching”.

  The impedance matching device 2 is disposed between the transmission circuit 1 and the transmission antenna 4. The impedance matching device 2 mainly includes a traveling wave / reflected wave extraction unit 21, a reflection coefficient calculation unit 22, a phase determination unit 23, a first-type matching circuit 24, a first storage unit 25, and a first storage unit 25. Two types of matching circuit 26, second storage unit 27, adjustment direction determination unit 28, adjustment step width determination unit 29, read position determination unit 30, through circuit 31, switch unit 32, and matching circuit A selection unit 33, a storage unit selection unit 34, and a control value output unit 35 are provided.

  The traveling wave / reflected wave extraction unit 21 corresponds to the voltage of the signal component corresponding to the transmission signal input from the transmission circuit 1 (hereinafter referred to as “traveling wave voltage Vf”) and the reflected signal from the transmission antenna 4. The signal component voltage (hereinafter also referred to as “reflected wave voltage Vr”) is separated and extracted. The traveling wave / reflected wave extraction unit 21 is preferably a directional coupler. The traveling wave / reflected wave extraction unit 21 may be a circulator, but in this case, it is necessary to further include an attenuator to extract a traveling wave of a predetermined level.

  The reflection coefficient calculation unit 22 calculates the absolute value of the reflection coefficient “Γ” (also referred to as “reflection coefficient absolute value | Γ |”) from the traveling wave voltage Vf and the reflected wave voltage Vr. Specifically, the reflection coefficient calculation unit 22 calculates the reflection coefficient absolute value | Γ | according to the following equation (1).

  When the first impedance matching is performed, the phase determination unit 23 determines whether the phase of the traveling wave voltage Vf and the phase of the reflected wave voltage Vr are close to the same phase or close to the opposite phase (also referred to as “first phase determination”). I do. As will be described later, in the initial state, the phase of the traveling wave voltage Vf and the phase of the reflected wave voltage Vr are substantially in phase or almost in phase.

  In addition, the phase determination unit 23 determines whether the phase of the reflected wave voltage Vr is advanced or delayed from the phase of the traveling wave voltage Vf when performing the second impedance matching (also referred to as “second phase determination”). Call).

  The first type matching circuit 24 includes a variable inductor element 240 inserted in series between the transmission circuit 1 and the transmission antenna 4, and a variable capacitor element 241 connected in parallel to the end on the transmission antenna 4 side. Prepare. The first storage unit 25 associates control values necessary for matching the transmission system 100 with a predetermined impedance value using the first-type matching circuit 24 with each value range of the reflection coefficient absolute value | Γ |. And store it on the table. As will be described later, the first storage unit 25 stores an index (hereinafter referred to as “index Idx”) that is a serial number assigned in order from the range of the small reflection coefficient absolute value | Γ |.

  Hereinafter, the “control value Tc” refers to a control value input to the matching circuits 24 and 26 of the first format or the second format. Here, the control value Tc is also referred to as an inductance value (also referred to as “inductance correction amount Lm”) and a capacitance value (also referred to as “capacitance correction amount Cm”) set in the matching circuits 24 and 26 of the first type or the second type. ). As will be described later, the control value Tc corresponds to the transmission circuit 1 when the gap Gp is changed with the electromagnetic resonance coupling transmission antenna 4 and a reception antenna (not shown) (not shown) facing each other. Is set based on the locus of the change of the input impedance when the transmitting antenna 4 side is viewed.

  The second type matching circuit 26 includes a variable inductor element 260 inserted in series between the transmission circuit 1 and the transmission antenna 4, and a variable capacitor element 261 connected in parallel to the end on the transmission circuit 1 side. Prepare. The second storage unit 27 uses the second-type matching circuit 26 to provide a control value Tc necessary for matching the transmission system 100 to a predetermined impedance value in each value range of each reflection coefficient absolute value | Γ |. Store it on the table in correspondence. As will be described later, each storage unit stores an index Idx assigned in order from a range of small reflection coefficient absolute values | Γ |.

  Hereinafter, the first-type matching circuit 24 and the second-type matching circuit 26 are also simply referred to as “matching circuit”. Further, the first storage unit 25 and the second storage unit 27 are simply collectively referred to as “storage unit”.

  When the transmission system 100 is in the post-matching state, the adjustment direction determination unit 28 reads the control value Tc from the storage unit based on the determination result of the second phase determination (also referred to as “second phase determination result Jr2”). The direction of the reading position (hereinafter also referred to as “reading direction Didx”) is determined. Here, the “reading direction Didx” indicates the direction of the index Idx corresponding to the control value Tc to be used next when the index Idx corresponding to the currently used control value Tc is used as a reference.

  The adjustment step width determination unit 29 determines whether or not the control value Tc to be used needs to be changed from the current control value Tc based on the reflection coefficient absolute value | Γ | when the transmission system 100 is in the post-matching state. In addition to making a determination, a step (movement) width (referred to as “step width Widx”) of the index Idx when a new control value Tc is read is determined.

  When the transmission system 100 is in the post-matching state, the reading position determination unit 30 determines the storage unit that reads the control value Tc and its index Idx based on the reading direction Didx and the step width Widx.

  In the switch unit 32, either the first type matching circuit 24, the second type matching circuit 26, or the through circuit 31 including only an electric wire is electrically connected between the transmission circuit 1 and the transmission antenna 4. To work.

  When the first impedance matching is performed, the matching circuit selection unit 33 performs the first based on the reflection coefficient absolute value | Γ | and the result of the first phase determination (referred to as “first phase determination result Jr1”). The switch unit 32 is controlled so that either the matching circuit 24 of the type, the matching circuit 26 of the second type, or the through circuit 31 including only the electric wire is electrically connected to the transmission circuit 1 and the transmission antenna 4. Specifically, the matching circuit selection unit 33 determines that there is no need to match the impedance value when the reflection coefficient absolute value | Γ | is equal to or smaller than a predetermined threshold (referred to as “threshold | Γ | thr”). The through circuit 31 is selected. On the other hand, the matching circuit selection unit 33 determines that the impedance value needs to be matched when the reflection coefficient absolute value | Γ | is larger than the threshold value | Γ | thr, and the matching circuit 24 of the first type or the second type, 26 is selected. Here, the threshold value | Γ | thr preferably corresponds to a value that can suppress the loss due to reflection to 0.5%, that is, a value that can achieve the efficiency of 99.5% if there is no other loss-generating part. It may be set to 0.0707.

  In addition, the matching circuit selection unit 33 selects one of the first type matching circuit 24, the second type matching circuit 26, and the through circuit 31 based on the processing result of the reading position determination unit 30 when executing the second impedance matching. Controls the switch unit 32 to be connected to the transmission circuit 1 and the transmission antenna 4. The storage unit selection unit 34 selects whether to use the control value Tc stored in the first storage unit 25 or the second storage unit 27 based on the first phase determination result Jr1. In addition, the storage unit selection unit 34 selects whether to use the control value Tc stored in the first storage unit 25 or the second storage unit 27 based on the processing result of the reading position determination unit 30. The control value output unit 35 reads a desired control value Tc from the selected first or second storage unit 25 or 27 during the first impedance matching or the second impedance matching, and is selected by the matching circuit selection unit 33. The control value Tc is reflected in the first type matching circuit 24 or the second type matching circuit 26.

[Transceiver antenna]
Next, the characteristics of a single transmission / reception antenna used in the electromagnetic resonance coupling method and its equivalent circuit expression will be described. FIG. 2 shows an example of the antenna used as the transmission antenna 4 and the reception antenna according to the present embodiment. The antenna shown in FIG. 2 is an open-ended helical antenna having a diameter of 30 cm, a winding number of 5, a pitch between windings of 5 mm, and a copper wire thickness of 2 mm.

  FIG. 3 shows the result of analyzing the input impedance of the antenna shown in FIG. 2 with a three-dimensional electromagnetic field analysis simulator. In FIG. 3, graphs “Gr1” and “Gr2” correspond to the real part of the input impedance, and graphs “Gi1” and “Gi2” correspond to the imaginary part of the input impedance. As shown in FIG. 3, the antenna shown in FIG. 2 corresponds to the real part at the series resonance point (that is, a point that crosses 0Ω when the graph Gi1 corresponding to the imaginary part changes from the minus side to the plus side). The graph Gr1 is almost 0Ω. Therefore, it can be seen that even if this antenna is used alone, it hardly radiates.

  The antenna shown in FIG. 2 can be accurately modeled by a series-parallel equivalent circuit. FIG. 4 is an example of a series-parallel equivalent circuit of the antenna shown in FIG. Here, by solving the simultaneous equations obtained from the frequency characteristics shown in FIG. 3 and determining the values of the circuit elements constituting the equivalent circuit of FIG. 4, the inductance L of the coil shown in FIG. The series capacitance C of the capacitor arranged in series is calculated to be 12.6 pF, the parallel capacitance Ct of the capacitor arranged in parallel with the coil is calculated to be 11.4 pF, and the resistance R is calculated to be 0.81Ω. The series resonance point in FIG. 3 is used for power transmission as a phenomenon of electromagnetic resonance coupling, and the resonance frequency is calculated to be 15.7 MHz.

  Here, the validity of the series-parallel equivalent circuit shown in FIG. 4 will be described. When the circuit shown in FIG. 4 is viewed from the left side, the input impedance “Zin” is expressed by Expression (2).

  From Equation (2), the real part (Re) and imaginary part (Im) of the input impedance Zin are obtained as shown in Expression (3).

  In FIG. 5, the value of the equivalent circuit element of the antenna obtained previously (L = 8.14 μH, C = 12.6 pF, Ct = 11.4 pF, R = 0.81Ω) is substituted into Equation (2). The graph which plotted both the calculated | required frequency characteristic and the result of the electromagnetic field analysis of FIG. 3 is shown. Specifically, FIG. 5A shows the relationship between the real part of the input impedance Zin and the frequency. FIG. 5B shows the relationship between the imaginary part of the input impedance Zin and the frequency. 5A and 5B, the equivalent circuit analysis result of FIG. 4 is represented by a solid line, and the electromagnetic field analysis result of FIG. 3 is represented by a dotted line.

  As shown in FIGS. 5A and 5B, the solid line showing the result of the equivalent circuit analysis in FIG. 4 and the dotted line showing the result of the electromagnetic field analysis in FIG. 3 almost coincide with each other. Therefore, it is valid to model the electromagnetic resonance coupling type antenna by the series-parallel type equivalent circuit shown in FIG. Later, using the series-parallel equivalent circuit shown in FIG. 4, a locus of change in input impedance when the transmitting antenna 4 and the receiving antenna are combined (hereinafter referred to as “input impedance locus Tr”) is obtained.

[Change path of input impedance]
Next, the input impedance locus Tr when the coupling state between the transmission antenna 4 and the reception antenna is changed will be described in detail.

  FIG. 6 shows the positional relationship between the transmitting antenna 4 and the receiving antenna during power transmission. FIG. 6 shows a system in which power is transmitted with the antenna shown in FIG. 2 facing the transmitting antenna 4 and the receiving antenna. In general, the gap Gp is generally about several tens of centimeters. Power feeding to the transmitting antenna 4 (power feeding from the signal generator in FIG. 6) and extraction of power from the receiving antenna are performed by connecting a coaxial cable or the like. In FIG. 6, power is extracted from the receiving antenna by connecting a load.

  FIG. 7 represents the system shown in FIG. 6 with a series-parallel equivalent circuit. That is, the series-parallel equivalent circuit shown in FIG. 7 has two electromagnetic resonance coupling transmission / reception antennas facing each other, feeds the transmission antenna 4 with a coaxial cable or the like, and connects the reception antenna and the load with a coaxial cable or the like. Show the system. In this example, the transmission antenna 4 and the reception antenna are the same antenna. Here, “Lm” in FIG. 7 represents the mutual inductance when the transmitting and receiving antennas are magnetically coupled. When the same antenna is used for the transmitting antenna 4 and the receiving antenna, the mutual inductance Lm is the coupling coefficient. Is represented by equation (4).

  The value of the coupling coefficient k is determined by the gap Gp between the transmitting and receiving antennas. Therefore, changing the gap Gp is equivalent to changing the coupling coefficient k.

Here, it is assumed that the impedance “Rx” of the load is equal to the signal source impedance on the transmission side, and that the impedance Rx of the load is equal to the matching target impedance “Z ₀ ” from the transmission circuit 1 side (signal source) to the transmission antenna 4. The input impedance Zin when looking at is expressed by equation (5).

Here, it is assumed that the resonance frequency “f ₀ ” of the transmission / reception antenna alone is used as the drive frequency (that is, the radio frequency used for power transmission). Here, the resonance frequency f ₀ is represented by the formula (6) shown below.

The input impedance Zin of the equation (5) is expressed by the equation (8) when the resonance frequency f ₀ (ω ₀ = 2πf ₀ ) is used and the fact that the equation (7) is established.

  Here, in equation (8), the coupling coefficient k is expressed as a parameter using the relationship of equation (4).

  Expression (5) and Expression (8) are shown as an example when the transmission antenna 4 and the reception antenna having the same shape are used. For example, when the size (diameter) of the reception antenna is reduced, transmission is performed. Even when the shapes of the antenna 4 and the receiving antenna are different (however, the resonance frequencies need to be the same), the value of the input impedance when the transmitting antenna 1 is viewed from the transmitting circuit 1 by the same procedure. (Requires an expression corresponding to the expression (5)), and the resonance frequency condition described in the expression (7) (this condition is an expression using values of L1 and C1 corresponding to the transmission antenna 4; (Two of the equations using the values of L2 and C2 corresponding to the receiving antenna will be used.), The equation corresponding to equation (8) can be obtained.

FIG. 8 shows the locus of the input impedance Zin (ω = ω ₀ ) when the coupling coefficient k is changed (that is, when the gap Gp between the transmitting and receiving antennas is changed) using Equation (8). Is a diagram plotted on a Smith chart. In FIG. 8, the coupling coefficient k changes in the range of 0.001 to 0.7. FIG. 9 is a diagram supplementarily describing an explanation to be described later in the Smith chart of FIG.

As shown in FIG. 8, in the electromagnetic resonance coupling method, when the gap Gp between the transmission and reception antennas is changed, the input impedance when the transmission antenna 4 is viewed from the transmission circuit 1 side greatly changes. The center point (also referred to simply as “center point”) of the Smith chart shown in FIG. 8 is in a state where impedance matching is performed (in this case, Z ₀ = 50Ω, hereinafter “matching state”). Or “matching point”). And the state which moved to the right from the center point represents that the input impedance is higher than that of the matching point. Conversely, a state of moving to the left side from the center point indicates that the input impedance is lower than that of the matching point. In other words, the state moved to the right from the center point (corresponding to the inside of the broken line frame WR in FIG. 9) is a case where the gap Gp between the transmitting and receiving antennas from the matching point is made smaller, that is, the coupling between the transmitting and receiving antennas than the matching point This is a condition that occurs when the is strong. On the contrary, the state moved to the left from the center point (corresponding to the inside of the broken line WL in FIG. 9) is when the gap Gp between the transmitting and receiving antennas from the matching point is increased, that is, the coupling between the transmitting and receiving antennas from the matching point This is a condition that occurs when it is small.

[Concept of impedance matching in the present invention]
As shown in FIGS. 8 and 9, the input impedance changes by changing the coupling state (ie, gap Gp) between the transmitting and receiving antennas. On the other hand, the change in the input impedance is a change close to one dimension slightly curved along the horizontal axis (resistance axis) of the Smith chart. What is characteristic is that the reactance component changes near the resistance axis where the reactance component is “0”. In such a case, the value of the phase component “arg (Γ)” of the complex reflection coefficient at the obtained point on the input impedance locus Tr is slightly curved when the coupling is strong (in the broken line frame WR in FIG. 9). If the coupling is weak (within the broken line frame WL in FIG. 9), it is almost 180 degrees. This is because the relationship between the phase of the traveling wave voltage Vf corresponding to the input signal to the transmitting antenna 4 and the phase of the reflected wave voltage Vr corresponding to the reflected signal returning from the transmitting antenna 4 due to the mismatch of impedance values is The former indicates almost the same phase, and the latter indicates the opposite phase.

  FIG. 10 shows a result of measuring a traveling wave voltage Vf and a reflected wave voltage Vr by modeling a transmission / reception antenna using the above-described series-parallel equivalent circuit and inserting a directional coupler between the transmission circuit 1 and the transmission antenna 4. . Specifically, FIG. 10A corresponds to the case where the coupling between the transmitting and receiving antennas is strengthened from the matching point, and FIG. 10B corresponds to the case where the coupling between the transmitting and receiving antennas is weakened from the matching point. . 10A and 10B, “Gvf” corresponds to the measurement result of the traveling wave voltage Vf, and “Gvr1” is the measurement of the reflected wave voltage Vr when the coupling coefficient k is 0.07. “Gvr2” corresponds to the measurement result of the reflected wave voltage Vr with a coupling coefficient k of 0.08, and “Gvr3” corresponds to the measurement of the reflected wave voltage Vr when the coupling coefficient k is 0.1. “Gvr4” corresponds to the measurement result of the reflected wave voltage Vr when the coupling coefficient k is 0.14, and “Gvr5” corresponds to the reflected wave voltage Vr when the coupling coefficient k is 0.2. It corresponds to the measurement result. “Gvr6” corresponds to the measurement result of the reflected wave voltage Vr when the coupling coefficient k is 0.05, and “Gvr7” is the measurement result of the reflected wave voltage Vr when the coupling coefficient k is 0.04. “Gvr8” corresponds to the measurement result of the reflected wave voltage Vr when the coupling coefficient k is 0.03, and “Gvr9” corresponds to the reflected wave voltage Vr when the coupling coefficient k is 0.02. It corresponds to the measurement result.

  In this way, by examining the phase relationship between the traveling wave voltage Vf and the reflected wave voltage Vr (whether it is in phase or in phase), the impedance matching device 2 determines that the position of the input impedance on the Smith chart is a broken line. It can be grasped whether it is in the frame WR or in the broken line frame WL.

  In addition, the example of the value of the coupling coefficient k shown here uses an antenna having a diameter of 30 cm, a number of turns of 5, a pitch between windings of 5 mm, and a copper wire thickness of 2 mm as the transmitting antenna 4 and the receiving antenna of FIG. If it was. When the antenna size and other structural parameters change, the value of the coupling coefficient k shown here can also change.

  Using this feature, the impedance matching device 2 according to the present embodiment operates in two ways as a pattern of impedance matching operation. Specifically, the impedance matching device 2 according to the present embodiment includes a first-type matching circuit 24 and a second-type matching circuit 26 as matching circuits, and the traveling wave voltage Vf and the reflected wave voltage Vr. Use properly based on the phase relationship. FIG. 11A shows a configuration example of the matching circuit 24 of the first format. FIG. 11B shows a configuration example of the matching circuit 26 of the second format. Then, when the traveling wave voltage Vf and the reflected wave voltage Vr are in phase, the impedance matching device 2 is in a state in which the coupling between the transmitting and receiving antennas is stronger than the matching point because the gap Gp becomes smaller from the matching point. The first type matching circuit 24 is used. On the other hand, when the traveling wave voltage Vf and the reflected wave voltage Vr are in opposite phases, the impedance matching device 2 is in a state in which the coupling between the transmitting and receiving antennas is weaker than the matching point due to the gap Gp increasing from the matching point. And the second type matching circuit 26 is used.

  Here, the variable inductor elements 240 and 260 and the variable capacitor elements 241 and 261 used in the matching circuit will be supplementarily described. As a method for realizing the variable inductor elements 240 and 260 and the variable capacitor elements 241 and 261, a known method can be used. For example, the variable inductor elements 240 and 260 connect a minute inductor in series and realize an inductor having a predetermined value by switching, and the variable capacitor elements 241 and 261 connect a minute capacitor in parallel and perform predetermined switching by switching. A capacitor having a value of is realized. As another realization means, the variable capacitor elements 241 and 261 may be a variable capacitor such as a vacuum capacitor or an air variable condenser. In that case, the rotation axis portion of the variable capacitor elements 241 and 261 is rotated using mechanical means such as a stepping motor. Furthermore, the variable capacitor elements 241 and 261 may be semiconductor elements such as variable capacitance diodes (varactor diodes) although they are not suitable for high power applications.

  FIG. 12 shows an arbitrary point on the input impedance locus Tr shown in FIG. 9 on the Smith chart using the first type or second type matching circuits 24 and 26 shown in FIGS. A schematic diagram is shown in which it is moved along the equal resistance circle and the equal conductance circle to reach the matching point of 50Ω.

  First, the case where the traveling wave voltage Vf and the reflected wave voltage Vr are substantially in phase, that is, the case where the impedance point to be matched exists in the broken line frame WR will be described. Here, as a representative example, it is assumed that an impedance point to be matched exists at the position Pr. In this case, the impedance matching device 2 moves the position Pr clockwise by a predetermined susceptance correction amount “A” on the equal conductance circle using the first type matching circuit 24 shown in FIG. Next, a predetermined reactance correction amount “B” is moved clockwise on the equal resistance circle C1 of the normalized resistance “r = 1” (see arrow Y2). Thereby, the impedance matching device 2 can move the impedance point to be matched to the matching point. The method for determining the susceptance correction amount A and the reactance correction amount B will be described later.

  Next, the case where the traveling wave voltage Vf and the reflected wave voltage Vr are in opposite phases, that is, the case where the impedance point to be matched exists within the broken line frame WL will be described. Here, as a representative example, it is assumed that an impedance point to be matched exists at the position Pl. In this case, the impedance matching device 2 moves the position Pl clockwise by a predetermined reactance correction amount “C” on the equal resistance circle using the second-type matching circuit 26 shown in FIG. Next, move it by a predetermined susceptance correction amount “D” clockwise on an equal conductance circle of normalized conductance “g = 1” (see arrow Y4). Thereby, the impedance matching device 2 can move the impedance point to be matched to the matching point. A method for determining the reactance correction amount C and the susceptance correction amount D described above will be described later.

  Considering the above, the impedance matching device 2 calculates the correction amounts A to D described above for each position on the input impedance trajectory Tr to be matched, and stores them in the first and second storage units 25 and 27. Remember. Thereby, the impedance matching apparatus 2 can obtain the above-described correction amounts A to D necessary for matching by knowing where the impedance point is when performing impedance matching.

  Here, the impedance matching device 2 specifies the correction amounts A to D with reference to the first and second storage units 25 and 27 based on the reflection coefficient absolute value | Γ |. This will be supplementarily described. Since the reflection coefficient absolute value | Γ | is equal to the distance from the center point of the Smith chart to the impedance point, the same reflection coefficient absolute value is obtained when there is an impedance point within the broken line frame WR and when there is an impedance point within the broken line frame WL. There is a pair of impedance points with the value | Γ |. However, as for the phase of the reflection coefficient absolute value | Γ |, the former has a value close to 0 degrees and the latter has a value close to 180 degrees. Therefore, the impedance matching device 2 can clearly distinguish between the traveling wave voltage Vf and the reflected wave voltage Vr by specifying whether the phases of the traveling wave voltage Vf and the reflected wave voltage Vr are substantially in phase or almost in phase.

  Considering the above, the impedance matching device 2 is used when the traveling wave voltage Vf and the reflected wave voltage Vr are in phase as a reference source for storing the control value Tc necessary for matching for each reflection coefficient absolute value | Γ |. Two storage units (tables) are prepared: a first storage unit 25 to be referred to, and a second storage unit 27 to be referred to when the traveling wave voltage Vf and the reflected wave voltage Vr are in opposite phases. The storage capacity required for the storage unit is determined in consideration of only the one-dimensional input impedance locus Tr slightly curved near the real axis on the Smith chart. Therefore, the required memory size can be significantly reduced as compared with the case where both real and imaginary values are required for matching.

  The impedance matching device 2 performs the above-described processing when the coupling coefficient k is smaller than the coupling coefficient k corresponding to the intersection of the equal resistance circle C1 with the normalized resistance “r = 1” and the input impedance locus Tr. By performing, the impedance point at the time of performing matching can be suitably changed to the matching point. In particular, in the electromagnetic resonance coupling method employed in the present embodiment, the coupling coefficient smaller than the coupling coefficient k corresponding to the intersection of the equal resistance circle C1 with the normalized resistance “r = 1” and the input impedance locus Tr. k is used. Therefore, the impedance matching device 2 of the present embodiment can move an arbitrary impedance point to the matching point.

[Control value generation method]
The correction amounts A to D described above for each impedance point on the derived input impedance locus Tr are calculated using Smith chart theoretical formulas. The capacitance correction amount Cm and the inductance correction amount Lm, which are control values Tc, are calculated based on the correction amounts A to D. This calculation will be described below. The capacitance correction amount Cm and the inductance correction amount Lm obtained by this calculation draw a graph composed of continuous values. However, as will be described later, the impedance matching device 2 stores in advance in the storage unit a table (also referred to as a “quantization table”) obtained by quantizing the above-described continuous values so as to have a size necessary for an application. A method for creating this quantization table will be described later.

(First storage unit)
First, a method for creating a table of the reflection coefficient absolute value | Γ | and the control value Tc stored in the first storage unit 25 will be described. The first storage unit 25 is used when the traveling wave voltage Vf and the reflected wave voltage Vr are substantially in phase.

  FIG. 13 is a diagram schematically illustrating a method of creating a table of reflection coefficient absolute values | Γ | and control values Tc stored in the first storage unit 25. Assume that the impedance point to be matched is at “Zin” in the figure. The impedance point Zin is on an equal conductance circle with a normalized conductance “g = gin” and an equal susceptance circle with a normalized susceptance “b = bin”. First, the coordinates (u, v) of the intersection “A” between the equal conductance circle of “g = gin” where the point of the impedance point Zin exists and the equal resistance circle of normalized resistance “r = 1” are as follows: It is represented by equation (9).

  Here, the normalized susceptance correction amount “Δb” necessary for moving the point of the impedance point Zin to the intersection A along the isoconductance circle of “g = gin”, and the point of the intersection A “r = The normalized reactance correction amount “Δx” required for moving to the center of the Smith chart along the equal resistance circle of “1” is based on the theoretical formula of the equal susceptance circle and the theoretical formula of the equal reactance circle. It can be expressed as shown in

  As shown in Expression (10), the normalized susceptance correction amount “Δb” is adjusted by a slight curve by subtracting the normalized susceptance “bin” of the impedance point Zin. The normalized reactance correction amount Δx corresponds to the reactance correction amount B described above, and the normalized susceptance correction amount Δb corresponds to the susceptance correction amount A described above.

Finally, Equation (11) that represents the actual capacitance correction amount Cm and inductance correction amount Lm by the obtained normalized reactance correction amount Δx and normalized susceptance correction amount Δb is shown below. The variable “f” used at this time indicates the drive frequency (unit: Hz), and “Z ₀ ” indicates the impedance value of the matching target.

  The impedance point Zin on the input impedance trajectory Tr has a one-to-one correspondence with the reflection coefficient absolute value | Γ | if only the right side of the Smith chart is considered, as shown in the following equation (12).

  Therefore, each impedance point Zin on the input impedance trajectory Tr is converted into the reflection coefficient absolute value | Γ | according to the equation (12), and the capacitance correction amount Cm obtained in advance according to the equation (11) for each value. Then, a table in which a set of values of the inductance correction amount Lm is associated is generated and stored in the first storage unit 25. Here, the above-described table is prepared as a table having a memory size necessary and permitted by the application. Thereby, the impedance matching device 2 can specify the capacitance correction amount Cm and the inductance correction amount Lm necessary for matching based on the reflection coefficient absolute value | Γ |.

14 (a) and 14 (b) show the reflection coefficient absolute value | Γ | prepared for a tip open type helical antenna (see FIG. 2) having a diameter of 30 cm, a winding number of 5, a winding pitch of 5 mm, and a copper wire thickness of 2 mm. Is a map (graph) showing the relationship between the control value and the control value Tc. Specifically, FIG. 14A is a graph showing the relationship between the capacitance correction amount Cm and the reflection coefficient absolute value | Γ |, and FIG. 14B shows the inductance correction amount Lm and the reflection coefficient absolute value |. It is a graph which shows the relationship with (GAMMA) |. In this case, the resonant frequency f is 15.7 MHz, and the matching target impedance Z ₀ is 50Ω.

  As will be described later, the impedance matching device 2 holds, in the first storage unit 25, a quantization table created at a resolution required by the application based on the values shown in FIGS. 14 (a) and 14 (b). .

(Second storage unit)
Next, a method for creating a table of the reflection coefficient absolute value | Γ | and the control value Tc stored in the second storage unit 27 will be described. The second storage unit 27 is used when the traveling wave voltage Vf and the reflected wave voltage Vr are substantially in reverse phase.

  FIG. 15 is a diagram schematically illustrating a method for creating a table stored as the second storage unit 27. Assume that the impedance point to be matched is at “Zin” in the figure. The impedance point Zin is on an equal resistance circle of normalized resistance “r = rin” and an equal reactance circle of normalized reactance “x = xin”. First, the coordinates (u, v) of the intersection “D” between the equal resistance circle of “r = rin” where the point of the impedance point Zin exists and the equal conductance circle of the normalized conductance “g = 1” are as follows: It can be expressed as shown in equation (13).

  Here, the normalized reactance correction amount “Δx” necessary for moving the impedance point Zin along the equal resistance circle of “r = rin” to the intersection “D”, and the point of the intersection D as “g = The normalized susceptance correction amount “Δb” required for moving to the center point along the isoconductance circle of “1” is expressed by the equation (14) based on the theoretical equation of the isosusceptance circle and the theoretical equation of the isoreactance circle. It can be expressed as follows.

  As shown in Expression (14), the normalized reactance correction amount Δx is adjusted by a slight curve by subtracting the normalized reactance xin of the impedance point Zin. The normalized susceptance correction amount Δb corresponds to the susceptance correction amount D described above, and the normalized reactance correction amount Δx corresponds to the reactance correction amount C described above.

Finally, the equation (15) representing the actual inductance correction amount Lm and the capacitance correction amount Cm for the obtained correction amounts is shown below. The variable “f” used at this time is the drive frequency (unit: Hz), and “Z ₀ ” is the impedance value of the matching target.

  Accordingly, as in the case where the traveling wave voltage Vf and the reflected wave voltage Vr are substantially in phase, each impedance point Zin is converted into a reflection coefficient absolute value | Γ | according to the equation (15), A table in which the set of the inductance correction amount Lm and the capacitance correction amount Cm obtained according to the equation (15) is associated is stored in the second storage unit 27. This table is prepared as a table having a memory size required and allowed by the application. Thereby, the impedance matching device 2 can specify the capacitance correction amount Cm and the inductance correction amount Lm necessary for impedance matching based on the reflection coefficient absolute value | Γ |.

FIGS. 16 (a) and 16 (b) show the reflection coefficient absolute value | Γ | prepared for a tip open type helical antenna (see FIG. 2) having a diameter of 30 cm, a number of turns of 5, a pitch between windings of 5 mm, and a copper wire thickness of 2 mm. Is a map (graph) showing the relationship between the control value and the control value Tc. In this case, the resonant frequency f is 15.7 MHz, and the matching target impedance Z ₀ is 50Ω.

  As will be described later, the impedance matching device 2 stores, in the second storage unit 27, a quantization table created at a resolution required by the application based on the values shown in FIGS. 16 (a) and 16 (b). .

[How to create a quantization table]
Next, a method of creating a quantization table that is actually stored in the impedance matching device 2 as a storage unit from the graphs shown in FIGS. 14 and 16 will be specifically described.

  The graphs showing the control values Tc shown in FIGS. 14 and 16 are continuous values. However, in reality, the impedance matching device 2 needs to hold a table obtained by quantizing these graphs so as to have a size necessary for an application. Here, “quantization” means the range (value range) of the reflection coefficient absolute value | Γ | in which the same inductance correction amount Lm and capacitance correction value Cm are used for a certain range of reflection coefficient absolute value | Γ |. Determining and determining representative values (also referred to as “quantized representative values”) of the inductance correction amount Lm and the capacitance correction value Cm used in each value range of the divided reflection coefficient absolute value | Γ |. Hereinafter, the boundary of each range (value range) of the above-described reflection coefficient absolute value | Γ | is referred to as a “quantization boundary”. Quantization is performed using iterative processing. Schematically, in the quantization, the quantization boundary and the quantization representative value are alternately obtained so that the reflection coefficient absolute value | Γ | is equal to or less than a preset threshold value | Γ | thr even in the vicinity of the quantization boundary. To be executed.

  Here, as an input for the quantization processing of the control value Tc, consider a table composed of a capacitance correction amount Cm and an inductance correction amount Lm that are so accurate that they can be regarded as a continuous amount corresponding to the reflection coefficient absolute value | Γ |. This table is originally obtained on the input impedance trajectory Tr obtained by changing the coupling coefficient k, and a corresponding coupling coefficient k exists in each row of the table. By changing the coupling coefficient k, the input impedance trajectory Tr is moved.

  When generating the table (first storage unit 25) referred to when the traveling wave voltage Vf and the reflected wave voltage Vr are in phase, the coupling coefficient k is slightly increased, and the traveling wave voltage Vf and the reflected wave voltage Vr are in opposite phases. At the time of generating the table (second storage unit 27) to be referred to in this case, the coupling coefficient k is slightly reduced to intentionally deteriorate the matching state, and the increase state of the reflection coefficient absolute value | Γ | is observed. Then, the quantization boundary and the quantization representative value are alternately set based on whether or not the reflection coefficient absolute value | Γ | exceeds a predetermined threshold value | Γ | thr.

Procedures 1 to 11 showing specific processing procedures will be described below. In the following, “updating the coupling coefficient k” refers to adding a predetermined value to the coupling coefficient k when generating the first storage unit 25, and generating the second storage unit 27. In this case, it means to subtract a predetermined value from the coupling coefficient k.
(1) Initialization Procedure 1: The coupling coefficient k is set so that it becomes a matching point in a state where the switch unit 32 selects the through circuit 31. The capacitance correction amount Cm and the inductance correction amount Lm are set to 0, respectively. Iterate the following:
(2) Processing for obtaining quantization boundary Procedure 2: Calculate the input impedance at the current coupling coefficient k.

  Procedure 3: Calculate an impedance value when a matching circuit (the initial values of Cm and Lm are 0) is added to the input impedance obtained in Procedure 2.

  Procedure 4: The reflection coefficient absolute value | Γ | is calculated from the impedance value obtained in Procedure 3.

Procedure 5: Check whether the reflection coefficient absolute value | Γ | exceeds a threshold value | Γ | thr. If not, the coupling coefficient k is updated and the procedure returns to step 2. If exceeded, the current coupling coefficient k and the corresponding reflection coefficient absolute value | Γ | are stored as quantization boundaries, and the process proceeds to step 6.
(3) Processing for obtaining quantized representative value Procedure 6: The coupling coefficient k is set to the value of the quantization boundary obtained in the procedures 2 to 5 immediately before. Also, the input impedance at this time is calculated.

  Procedure 7: The coupling coefficient k is updated, and the capacitance correction amount Cm and the inductance correction amount Lm corresponding to the values are set.

  Step 8: Calculate the impedance value when the capacitance correction amount Cm and the inductance correction amount Lm set in step 7 are added to the input impedance obtained in step 6.

  Procedure 9: Calculate the reflection coefficient absolute value | Γ | from the impedance value obtained in Procedure 8.

Procedure 10: Check whether the reflection coefficient absolute value | Γ | exceeds a threshold value | Γ | thr. If not, the coupling coefficient k is updated and the procedure returns to step 7. If it exceeds, the current coupling coefficient k, the current capacitance correction amount Cm, and the inductance correction amount Lm are stored as quantized representative values. Proceed to the end confirmation process (procedure 11).
(4) Completion confirmation process Procedure 11: If the coupling coefficient k has reached a predetermined end value, all processes are terminated. If it has not yet reached, the process returns to step 2 again to perform iterative processing.

Next, a specific example of a table stored in the first storage unit 25 generated by the above-described procedure 1 to procedure 11 will be described. Hereinafter, the threshold value | Γ | thr is set to 0.0707. In this case, the loss due to reflection at the quantization boundary (corresponding to | Γ | ² ) is 0.5%.

  FIG. 17A shows a graph “Gcm1” indicating the transition of the capacitance correction amount Cm before quantization and a graph “Qcm1” indicating the transition of the capacitance correction amount Cm after quantization. FIG. 17B shows a graph “Glm1” indicating the transition of the inductance correction amount Lm before quantization and a graph “Qlm1” indicating the transition of the inductance correction amount Lm after quantization. As shown in FIGS. 17A and 17B, the capacitance correction amount Cm and the inductance correction amount Lm are such that the quantization interval (that is, the interval between the quantization boundaries) increases as the reflection coefficient absolute value | Γ | increases. Quantized to be small.

  FIG. 18 illustrates an example of a table actually held in the first storage unit 25. In the table shown in FIG. 18, the lower limit value of the quantization boundary of the reflection coefficient absolute value | Γ |, the lower limit value of the quantization boundary of the coupling coefficient k, the capacitance correction amount Cm, and the inductance correction amount Lm for each row. It is associated. Also, an index Idx from “0” to “12” is assigned to each value range of the reflection coefficient absolute value | Γ |. Here, the upper limit value of the quantization boundary of the reflection coefficient absolute value | Γ | and the upper limit value of the quantization boundary of the coupling coefficient k are the quantization of the reflection coefficient absolute value | Γ | corresponding to the index Idx that is smaller by one. It is determined based on the lower limit value of the boundary and the lower limit value of the quantization boundary of the coupling coefficient k. As shown in FIG. 18, the index Idx is assigned a larger value as the coupling coefficient k is larger. In addition, the 1st memory | storage part 25 does not necessarily need to memorize | store the value of the coupling coefficient k.

  Next, a specific example of the second storage unit 27 generated by the above-described procedure 1 to procedure 11 will be described.

  FIG. 19A shows a graph “Glm2” showing the transition of the inductance correction amount Lm before quantization and a graph “Qlm2” showing the transition of the inductance correction amount Lm after quantization. FIG. 19B shows a graph “Gcm2” showing the transition of the capacitance correction amount Cm before quantization and a graph “Qcm2” showing the transition of the capacitance correction amount Cm after quantization. As shown in FIGS. 19A and 19B, the capacitance correction amount Cm and the inductance correction amount Lm are quantized so that the quantization interval decreases as the reflection coefficient absolute value | Γ | increases. .

  FIG. 20 shows an example of a table actually held in the impedance matching device 2 as the second storage unit 27. In the table shown in FIG. 20, the lower limit value of the quantization boundary of the reflection coefficient absolute value | Γ |, the lower limit value of the quantization boundary of the coupling coefficient k, the capacitance correction amount Cm, and the inductance correction amount Lm for each row. It is associated. Also, an index Idx from “−1” to “−12” is assigned to each value range of the reflection coefficient absolute value | Γ |. Here, the upper limit value of the quantization boundary of the reflection coefficient absolute value | Γ | and the upper limit value of the quantization boundary of the coupling coefficient k are the quantization of the reflection coefficient absolute value | Γ | corresponding to the index Idx that is smaller by one. It is determined based on the lower limit value of the boundary and the lower limit value of the quantization boundary of the coupling coefficient k. As shown in FIG. 20, the index Idx is assigned a larger value as the coupling coefficient k is larger, as in FIG. Further, the index Idx is assigned serial numbers from “−12” to “12” through FIGS. 18 and 20, and a larger value is assigned as the coupling coefficient k is larger. Note that the second storage unit 27 does not necessarily store the value of the coupling coefficient k.

[Second impedance matching]
Next, the second impedance matching performed by the impedance matching device 2 in the post-matching state will be specifically described. Schematically, the impedance matching device 2 detects the reflection coefficient absolute value | Γ | at every predetermined period in the post-matching state, and whether or not the reflection coefficient absolute value | Γ | is larger than the threshold value | Γ | thr. To monitor. When the reflection coefficient absolute value | Γ | becomes larger than the threshold value | Γ | thr, the impedance matching device 2 determines whether the phase of the reflected wave voltage Vr is delayed or advanced from the phase of the traveling wave voltage Vf. Based on this, the reading direction Didx is determined. Here, as will be described later, when the phase of the reflected wave voltage Vr lags behind the phase of the traveling wave voltage Vf, the impedance matching device 2 moves in a direction in which the coupling of the transmitting and receiving antennas becomes stronger from the matching state. It is determined that the alignment is shifted, and the reading direction Didx is determined in the direction in which the index Idx increases. On the other hand, when the phase of the reflected wave voltage Vr is more advanced than the phase of the traveling wave voltage Vf, the impedance matching device 2 indicates that the matching is shifted from the matching state in a direction in which the coupling of the transmission / reception antenna is weakened. Judgment is made, and the reading direction Didx is determined in the direction in which the index Idx decreases.

  Hereinafter, the case where the matching is shifted in the direction in which the coupling of the transmission / reception antenna becomes strong and the case where the matching is shifted in the direction in which the coupling of the transmission / reception antenna becomes weak will be described separately.

(When the alignment shifts in the direction of strong coupling)
First, the case where the alignment is shifted in the direction in which the coupling of the transmission / reception antenna becomes stronger, that is, the case where the state of the transmission / reception antenna changes in the direction in which the coupling coefficient k increases will be described.

  FIG. 21A illustrates a traveling wave when the transmission system 100 is in a matching state by the first impedance matching when the coupling coefficient k is 0.1, and then the coupling coefficient k increases to 0.12 to 0.3. The waveform of the voltage Vf and each reflected wave voltage Vr is shown. Specifically, the graph “Gvr10” corresponds to the case where the coupling coefficient k is 0.1, that is, the matching state, and the graph “Gvr11” corresponds to the case where the coupling coefficient k is 0.12. “Gvr12” corresponds to the case where the coupling coefficient k is 0.15, the graph “Gvr13” corresponds to the case where the coupling coefficient k is 0.2, and the graph “Gvr14” has a coupling coefficient k of 0.3. This corresponds to the case. FIG. 21B shows a case where the transmission system 100 is in a matching state by the first impedance matching when the coupling coefficient k is 0.055, and then the coupling coefficient k increases from 0.06 to 0.10. The waveforms of the traveling wave voltage Vf and each reflected wave voltage Vr are shown. Specifically, the graph “Gvr15” corresponds to the case where the coupling coefficient k is 0.055, that is, the matching state, and the graph “Gvr16” corresponds to the case where the coupling coefficient k is 0.06. The graph “Gvr17” corresponds to a case where the coupling coefficient k is 0.07, the graph “Gvr18” corresponds to a case where the coupling coefficient k is 0.08, and the graph “Gvr19” has a coupling coefficient k of 0. This corresponds to the case of 10.

  Here, the graph Gvr10 illustrated in FIG. 21A corresponds to the case where the impedance point at the time of executing the first impedance matching is on the input impedance locus Tr in the broken line frame WR. On the other hand, the graph Gvr15 shown in FIG. 21B corresponds to the case where the impedance point at the time of executing the first impedance matching is on the input impedance locus Tr in the broken line frame WL. In any of these cases, when the alignment shifts in the direction in which the coupling becomes stronger, the phase of the reflected wave voltage Vr is delayed from the phase of the traveling wave voltage Vf (the graphs Gvr11 to Gvr14 and the graph). Gvr16-Gvr19). Note that the degree of the phase delay of the reflected wave voltage Vr is uniquely determined by the impedance point immediately before the execution of the first impedance matching. Specifically, the degree of the phase delay of the reflected wave voltage Vr becomes smaller as the impedance point is closer to the matching point that is the center point of the Smith chart.

  Further, as shown in FIGS. 21A and 21B, the deviation from the matching state is larger as the coupling coefficient k is farther from the matching state coupling coefficient k, that is, due to the increase in the coupling coefficient k. As it is, the level of the reflected wave voltage Vr increases. Also, from equation (1), the reflection coefficient absolute value | Γ | increases as the level (absolute value) of the reflected wave voltage Vr increases. Therefore, the larger the reflection coefficient absolute value | Γ | is, the larger the deviation from the alignment state is. Therefore, in this case, the adjustment step width determining unit 29 needs to set the step width Widx to be larger.

  Considering the above, the impedance matching apparatus 2 determines whether or not the matching state is deteriorated by monitoring the reflection coefficient absolute value | Γ | after the transmission system 100 is in the after-matching state. When the impedance matching device 2 determines that the reflection coefficient absolute value | Γ | is increased and the phase of the reflected wave voltage Vr is delayed from the phase of the traveling wave voltage Vf, the impedance matching device 2 is coupled between the transmitting and receiving antennas. It is specified that the alignment is shifted in the direction in which the intensity increases. That is, in this case, the adjustment direction determination unit 28 reads out the direction in which the coupling coefficient k increases from the index Idx corresponding to the control value Tc currently used, and the direction in which the index Idx increases in FIGS. Determined as direction Didx. Preferably, the adjustment step width determination unit 29 increases the step width Widx as the change width of the reflection coefficient absolute value | Γ | from the matching state increases. As a result, the impedance matching device 2 can quickly shift the transmission system 100 to the matching state again. Details of the method for determining the step width Widx by the adjustment step width determination unit 29 will be described later in the section [Step Width Determination Method]. Instead of the above description, the adjustment step width determination unit 29 may always set the step width Widx to a predetermined value (for example, “1”) regardless of the reflection coefficient absolute value | Γ |.

(When the alignment is shifted in the direction of weakening)
Next, a case where the matching is shifted in a direction in which the coupling of the transmission / reception antenna becomes weak, that is, a case where the state of the transmission / reception antenna changes in a direction in which the coupling coefficient k decreases will be described.

  FIG. 22A shows a traveling wave when the transmission system 100 is in a matching state by the first impedance matching when the coupling coefficient k is 0.1, and then the coupling coefficient k is decreased to 0.05 to 0.09. The waveform of the voltage Vf and each reflected wave voltage Vr is shown. Specifically, the graph “Gvr10” corresponds to the case where the coupling coefficient k is 0.1, that is, the matching state, as in FIG. 21A, and the graph “Gvr21” has the coupling coefficient k of 0. The graph “Gvr22” corresponds to the case where the coupling coefficient k is 0.08, the graph “Gvr23” corresponds to the case where the coupling coefficient k is 0.07, and the graph “Gvr24” This corresponds to the case where the coupling coefficient k is 0.06, and the graph “Gvr25” corresponds to the case where the coupling coefficient k is 0.05. FIG. 22B shows a case where the transmission system 100 is in a matching state by the first impedance matching when the coupling coefficient k is 0.055, and then the coupling coefficient k is decreased to 0.02 to 0.05. The waveforms of the traveling wave voltage Vf and each reflected wave voltage Vr are shown. Specifically, the graph “Gvr15” corresponds to the case where the coupling coefficient k is 0.055, that is, the matching state, as in FIG. 21B, and the graph “Gvr26” has the coupling coefficient k of 0. .05, the graph “Gvr27” corresponds to the case where the coupling coefficient k is 0.04, the graph “Gvr28” corresponds to the case where the coupling coefficient k is 0.03, and the graph “Gvr29”. Corresponds to the case where the coupling coefficient k is 0.02.

  Here, the graph Gvr10 illustrated in FIG. 22A corresponds to the case where the impedance point at the time of executing the first impedance matching is on the input impedance locus Tr in the broken line frame WR. A graph Gvr15 shown in FIG. 22B corresponds to the case where the impedance point at the time of executing the first impedance matching is on the input impedance locus Tr in the broken line frame WL. In any of these cases, when the matching is shifted in the direction in which the coupling becomes weaker, the phase of the reflected wave voltage Vr is more advanced than the phase of the traveling wave voltage Vf (see graphs Gvr21 to Gvr29). Note that the degree of advance of the phase of the reflected wave voltage Vr is uniquely determined by the impedance point immediately before the execution of the first impedance matching. Specifically, the degree to which the phase of the reflected wave voltage Vr advances increases as the impedance point is closer to the matching point, which is the center point of the Smith chart.

  Further, as shown in FIGS. 22A and 22B, the deviation from the matching state becomes larger as the coupling coefficient k is farther from the matching state coupling coefficient k, that is, due to the increase in the coupling coefficient k. As it is, the level of the reflected wave voltage Vr increases. Also, from equation (1), the reflection coefficient absolute value | Γ | increases as the level of the reflected wave voltage Vr increases. Therefore, the larger the reflected wave coefficient absolute value | Γ | is, the larger the deviation from the matching state is. Therefore, in this case, the adjustment step width determining unit 29 needs to set the step width Widx to be larger.

  Considering the above, the impedance matching apparatus 2 determines whether or not the matching state is deteriorated by monitoring the reflection coefficient absolute value | Γ | after the transmission system 100 is in the after-matching state. When the impedance matching device 2 determines that the reflection coefficient absolute value | Γ | is increased and the phase of the reflected wave voltage Vr is advanced from the phase of the traveling wave voltage Vf, the impedance matching device 2 is coupled between the transmitting and receiving antennas. It can be specified that the alignment is shifted in the direction in which the weakening occurs. That is, in this case, the adjustment direction determination unit 28 determines the direction in which the coupling coefficient k decreases from the index Idx selected when the first impedance matching is executed, the direction in which the index Idx increases in FIGS. Can be determined as Preferably, the adjustment step width determination unit 29 increases the step width Widx as the change width of the reflection coefficient absolute value | Γ | from the matching state increases. As a result, the impedance matching device 2 can quickly shift the transmission system 100 to the matching state again. Note that, instead of the above description, the adjustment step width determination unit 29 may always set the step width Widx to a predetermined value regardless of the reflection coefficient absolute value | Γ |.

[Operation example and effect]
Next, a specific example of the operation of the impedance matching device 2 and the effects accompanying it will be described.

(First impedance matching)
First, the first impedance matching process that is executed when the transmission system 100 is in the initial state, that is, when impedance matching is not yet performed between the transmission circuit 1 and the transmission antenna 4 will be described.

  In the initial state, the impedance matching device 2 is inserted so that the through circuit 31 is connected between the transmission circuit 1 and the transmission antenna 4 by the switch unit 32. Here, it is assumed that the coupling coefficient k between the transmitting and receiving antennas is 0.095. This state belongs to a relatively strong coupling when the open-ended helical antenna shown in FIG. 2 is used. A directional coupler is used as the traveling wave / reflected wave extraction unit 21. The threshold value | Γ | thr is assumed to be 0.0707.

  First, the traveling wave / reflected wave extraction unit 21 extracts the traveling wave voltage Vf and the reflected wave voltage Vr. Then, the reflection coefficient calculation unit 22 calculates the reflection coefficient absolute value | Γ | based on the above-described equation (1).

  Further, the phase determination unit 23 determines the phase relationship between the traveling wave voltage Vf and the reflected wave voltage Vr, that is, whether they are in phase or in phase. When these are substantially in phase, the matching circuit selection unit 33 selects the first type matching circuit 24 and the storage unit selection unit 34 selects the first storage unit 25. On the other hand, when the above-described phase relationship is substantially opposite, the matching circuit selection unit 33 selects the second type matching circuit 26 and the storage unit selection unit 34 selects the second storage unit 27.

  FIG. 23A shows waveforms of the traveling wave voltage Vf and the reflected wave voltage Vr immediately before the execution of the first impedance matching. In FIG. 23A, the graph “Gvf” corresponds to the waveform of the traveling wave voltage Vf, and the graph “Gvr” corresponds to the waveform of the reflected wave voltage Vr. As shown in FIG. 23A, the traveling wave voltage Vf and the reflected wave voltage Vr are substantially in phase. Accordingly, the first storage unit 25 and the first type matching circuit 24 are selected. In FIG. 23A, the traveling wave voltage Vf is observed to be “15.8 mV” and the reflected wave voltage Vr is observed to be “6.3 mV”. Therefore, the reflection coefficient absolute value | Γ | is calculated as 0.40. FIG. 23B shows frequency characteristics of transmission efficiency. When the driving frequency is “15.7 MHz”, the transmission efficiency is 82%.

  Next, a process for selecting the control value Tc from the table stored in the first storage unit 25 will be described. On the table shown in FIG. 18, the index Idx corresponding to the reflection coefficient absolute value | Γ | being 0.40 is “3”, and the quantized representative value is that the capacitance correction amount Cm is “94 pF”. The inductance correction amount Lm is “587 nH”. The control value output unit 35 sets the capacitance correction amount Cm and the inductance correction amount Lm in the variable capacitor element 241 and the variable inductor element 240 of the first type matching circuit 24.

  FIG. 24A shows waveforms of the traveling wave voltage Vf and the reflected wave voltage Vr when impedance matching is performed based on the control value Tc. FIG. 24B shows frequency characteristics of transmission efficiency. In the graph of FIG. 24A, the traveling wave voltage Vf is observed as “15.8 mV”, the reflected wave voltage Vr is observed as “0.43 mV”, and the reflection coefficient absolute value | Γ | is calculated as 0.027. Therefore, the loss due to reflection is as very small as 0.07%. Further, the transmission efficiency is improved to 97.6% at the drive frequency of “15.7 MHz”.

(Second impedance matching)
Hereinafter, in the post-matching state, the second impedance matching process executed when the matching is deviated from the matching state due to the influence of the change in the coupling between the transmitting and receiving antennas will be described for each case.

1. Here, it is assumed that the gap Gp between the transmitting and receiving antennas is reduced and the coupling coefficient k is increased from 0.095 to 0.102. In the matching circuit, the control value Tc set by the first impedance matching, that is, the control value Tc having the index Idx in the table of the first storage unit 25 is still reflected. FIG. 25A shows waveforms of traveling wave voltage Vf and reflected wave voltage Vr corresponding to the above-described state. FIG. 25B shows frequency characteristics of transmission efficiency. In FIG. 25A, the traveling wave voltage Vf is observed as “15.8 mV”, the reflected wave voltage Vr is observed as “1.54 mV”, and the reflection coefficient absolute value | Γ | is calculated as 0.097. Therefore, in the state shown in FIG. 25, the loss of reflection due to mismatching increased to 0.95% due to the deterioration of matching. On the other hand, the transmission efficiency was 97.2%, which was slightly lowered but hardly changed.

  In the state shown in FIG. 25, the reflection coefficient absolute value | Γ | (0.097) exceeds a preset threshold value | Γ | thr (0.0707). Therefore, the impedance matching device 2 performs the second impedance matching.

  Here, comparing the phase of the traveling wave voltage Vf and the phase of the reflected wave voltage Vr in FIG. 25A, the phase of the reflected wave voltage Vr is delayed from the phase of the traveling wave voltage Vf. Therefore, in this case, the impedance matching device 2 can determine that the coupling between the transmitting and receiving antennas has shifted in the direction in which the coupling is strong. Then, the adjustment direction determination unit 28 determines the reading direction Didx in the direction in which the index Idx selected at the time of the first impedance matching is increased from 3 from the table shown in FIG. 18 stored in the first storage unit 25. Also, here, the adjustment step width determination unit 29 sets the step width Widx to “1” which is a predetermined value. Therefore, here, the storage unit selection unit 34 has the control value Tc corresponding to the case where the index Idx is “4” from the first storage unit 25, that is, the capacitance correction amount Cm is “87 pF” and the inductance correction amount Lm is “736 nH”) is extracted. Then, the control value output unit 35 sets the control value Tc in the matching circuit 24 of the first format.

  FIG. 26A shows the traveling wave voltage Vf and the reflected wave voltage Vr after the above-described control value Tc is set. FIG. 26B shows the transmission efficiency after the above-described control value Tc is set. In FIG. 26A, the traveling wave voltage Vf is observed as “15.73 mV”, the reflected wave voltage Vr is observed as “0.72 mV”, and the reflection coefficient absolute value | Γ | is calculated as 0.046. As described above, by updating the control value Tc set in the matching circuit, the reflection loss due to mismatching is reduced to 0.21%. Further, the transmission efficiency is 97.1%, and there is hardly any change.

  What should be noted here is that, as shown in FIGS. 24 (b), 25 (b), and 26 (b), once impedance matching is performed, the transmission efficiency hardly changes. That is, the impedance matching device 2 observes a change in the absolute value of the reflection coefficient | Γ | before the transmission efficiency is greatly adversely affected, and controls the value to be always equal to or less than a predetermined threshold value | Γ | thr. Thus, the transmission efficiency can always be maintained at a high level.

2. When matching is shifted in the direction of weak coupling Here, after impedance matching is performed once for the state where the coupling coefficient k is 0.095, the gap Gp between the transmitting and receiving antennas increases, and the coupling coefficient k becomes 0.085. The case where it becomes is described. In the matching circuit, the control value Tc set by the first impedance matching, that is, the control value Tc having the index Idx in the table of the first storage unit 25 is still reflected. FIG. 27A shows waveforms of traveling wave voltage Vf and reflected wave voltage Vr corresponding to the above-described state. FIG. 27B shows transmission efficiency corresponding to the above-described state. In FIG. 27A, the traveling wave voltage Vf is observed as “15.7 mV”, the reflected wave voltage Vr is observed as “1.29 mV”, and the reflection coefficient absolute value | Γ | is calculated as 0.082. As described above, the reflection loss due to mismatching increased to 0.68% as the matching deteriorated. On the other hand, as shown in FIG. 27 (b), the transmission efficiency at the drive frequency slightly decreased to 96.1%, but maintained a high value of 96% or more.

  In the state shown in FIG. 27, the reflection coefficient absolute value | Γ | (0.082) exceeds a preset threshold value | Γ | thr (0.0707). Therefore, the impedance matching device 2 performs the second impedance matching.

  Comparing the phase of the traveling wave voltage Vf and the phase of the reflected wave voltage Vr in FIG. 27A, the phase of the reflected wave voltage Vr is ahead of the phase of the traveling wave voltage Vf. Therefore, in this case, the impedance matching device 2 can determine that the coupling between the transmitting and receiving antennas has shifted in the direction of weakening. Then, the adjustment direction determination unit 28 sets the reading direction Didx in a direction to decrease the index Idx selected at the time of the first impedance matching from “3” from the table shown in FIG. 18 stored in the first storage unit 25. Determine. Also, here, the adjustment step width determination unit 29 sets the step width Widx to “1” which is a predetermined value. Therefore, here, the storage unit selection unit 34 has the control value Tc corresponding to the case where the index Idx is “2” from the first storage unit 25, that is, the capacitance correction amount Cm is “95 pF” and the inductance correction amount Lm is “443 nH”). Then, the control value output unit 35 sets the control value Tc in the matching circuit 24 of the first format.

  FIG. 28A shows the traveling wave voltage Vf and the reflected wave voltage Vr after the above-described control value Tc is set. FIG. 28B shows the transmission efficiency after the above-described control value Tc is set. In FIG. 28A, the traveling wave voltage Vf is observed as “15.8 mV”, the reflected wave voltage Vr is observed as “0.95 mV”, and the reflection coefficient absolute value | Γ | is calculated as 0.060. Then, by updating the control value Tc set in the matching circuit, the reflection loss due to mismatching is reduced to 0.36%. Further, the transmission efficiency is improved to 97.4% and maintains a high value.

  Thus, as in the case where the coupling gradually increases, as shown in FIGS. 24B, 27B, and 28B, the transmission efficiency after impedance matching once is 96%. It is maintained at a high value above. That is, the impedance matching device 2 observes a change in the absolute value of the reflection coefficient | Γ | before the transmission efficiency is greatly adversely affected, and controls the value to be always equal to or less than a predetermined threshold value | Γ | thr. Thus, the transmission efficiency can always be maintained at a high level.

  1 above. And 2. In the example described in (2), the case where the alignment is deviated from the relatively strong coupling state (k = 0.095) as the initial state has been described. However, the case where the alignment is deviated from the relatively weak coupling state is similarly dealt with. be able to. In this case, the impedance matching device 2 determines the control value Tc with reference to the table shown in FIG. 20 stored in the second storage unit 27.

[Step width determination method]
Next, a supplementary description will be given of a method for determining the step width Widx based on the reflection coefficient absolute value | Γ |.

  In the above-mentioned example of “2. When the alignment is shifted in the direction in which the coupling is weakened”, the step width Widx is fixed to “1”. However, when the reflection coefficient changes abruptly, if the index Idx is shifted one by one and the control value Tc is updated, it may take a considerable time to reach the index Idx related to the desired control value Tc. There is. That is, when power is supplied to a moving object using an electromagnetic resonance coupling system, a change in the gap Gp between the transmitting and receiving antennas and a positional deviation may occur at a high speed and with a large fluctuation range. is there. In such a case, it is expected that the amount of change described above within the period in which the reflection coefficient absolute value | Γ | In preparation for such a case, the impedance matching apparatus 2 preferably determines the step width Widx flexibly according to the change width of the reflection coefficient absolute value | Γ | from the matching state. Thereby, the impedance matching device 2 can quickly match even when the change of the gap Gp and the change of the positional deviation occur at high speed.

  Specifically, the following mounting methods can be considered.

  Here, it is assumed that the gap Gp is reduced from the matching state shown in FIG. 24 after the first impedance matching is performed, and the coupling coefficient k is changed from 0.095 to 0.12. At this time, the traveling wave voltage Vf and the reflected wave voltage Vr are “15.88 mV” and “4.03 mV”, respectively, and the reflection coefficient absolute value | Γ | is 0.254. In this case, it is assumed that the impedance matching apparatus 2 moves the index Idx from the current “3” by the step width Widx “2” in the direction in which the coupling becomes stronger to “5”. At this time, the control value Tc reflected in the matching circuit has a capacitance correction amount Cm of “78 pF” and an inductance correction amount Lm of “896 uH”. As a result, the traveling wave voltage Vf after reflecting the control value Tc is “15.74 mV”, the reflected wave voltage Vr is “0.484 mV”, and the reflection coefficient absolute value | Γ | is 0.03. As described above, the impedance matching device 2 can improve matching at once by appropriately setting the step width Widx.

  Further, it is assumed that the gap Gp is increased from the matching state shown in FIG. 24 after the first impedance matching is performed, and the coupling coefficient k is increased from 0.095 to 0.145. At this time, the traveling wave voltage Vf and the reflected wave voltage Vr are “15.97 mV” and “6.73 mV”, respectively, and the reflection coefficient absolute value | Γ | is 0.42. In this case, it is assumed that the impedance matching device 2 moves the index Idx from the current “3” by the step width Widx “3” in the direction in which the coupling becomes stronger to “6”. At this time, the control value Tc reflected in the matching circuit has a capacitance correction amount Cm of “69 pF” and an inductance correction amount Lm of “1070 uH”. As a result, the traveling wave voltage Vf is “15.76 mV”, the reflected wave voltage Vr is “0.344 mV”, and the reflection coefficient absolute value | Γ | is 0.022. As described above, the impedance matching device 2 can improve matching at once by appropriately setting the step width Widx.

From the above, as an example, a method of changing the step width Widx on the basis of the following can be considered.
・ When “| Γ | change width <0.15”, “Widx = 1”
・ When “| Γ | change width <0.30”, “Widx = 2”
・ When “| Γ | change width <0.45”, “Widx = 3”
・ In the case of “variation width of || Γ | ≧ 0.45”, “Widx = 4”
As described above, the impedance matching device 2 stores, for example, a table of appropriate step widths Widx corresponding to the variation widths of the respective reflection coefficient absolute values | Γ | in advance in a memory. The above table is created in advance based on, for example, experiments. The impedance matching device 2 determines the step width Widx from the change width of the reflection coefficient absolute value | Γ | with reference to this table, thereby rapidly changing the gap Gp between the transmitting and receiving antennas and the position shift. In such a case, the alignment state can be quickly recovered.

[Processing flow]
Next, a processing procedure in the first embodiment will be described. In the following, the first impedance matching processing procedure will be described first, and then the second impedance matching processing procedure will be described.

(First impedance matching)
FIG. 29 is a flowchart showing a processing procedure executed by the impedance matching apparatus 2 in the first embodiment. The impedance matching device 2 executes the process shown in FIG. 29 at a predetermined timing.

  First, the matching circuit selection unit 33 sets the switch unit 32 to the through circuit 31 (step S101). Then, the traveling wave / reflected wave extraction unit 21 measures the magnitudes of the traveling wave voltage Vf and the reflected wave voltage Vr (step S102). Then, the reflection coefficient calculation unit 22 calculates the reflection coefficient absolute value | Γ | (step S103). Specifically, the reflection coefficient calculation unit 22 refers to Equation (1) and calculates based on the traveling wave voltage Vf and the reflected wave voltage Vr.

  Next, the matching circuit selection unit 33 determines whether or not the reflection coefficient absolute value | Γ | is equal to or less than the threshold value | Γ | thr (step S104). Thereby, the matching circuit selection unit 33 determines whether or not impedance matching needs to be performed. If the reflection coefficient absolute value | Γ | is equal to or smaller than the threshold value | Γ | thr (step S104; Yes), the matching circuit selection unit 33 determines that it is not necessary to perform impedance matching, and sets the switch unit 32. It does not change. On the other hand, when the reflection coefficient absolute value | Γ | is larger than the threshold value | Γ | thr (step S104; No), the matching circuit selection unit 33 determines that impedance matching needs to be performed, and proceeds to step S105. .

  Next, the phase determination unit 23 performs the first phase determination based on the traveling wave voltage Vf and the reflected wave voltage Vr (step S105). Specifically, the phase determination unit 23 determines whether these voltages are close to the same phase or close to the opposite phase. When the phase determination unit 23 determines that the traveling wave voltage Vf and the reflected wave voltage Vr are close to the same phase (step S106; Yes), the storage unit selection unit 34 selects the first storage unit 25 (step S106). S107). And the memory | storage part selection part 34 reads the control value Tc corresponding to reflection coefficient absolute value | (GAMMA) | (step S108). Then, the control value output unit 35 sets the control value Tc in the first format matching circuit 24 (step S109). Then, the matching circuit selection unit 33 sets the switch unit 32 to the first type matching circuit 24 (step S110).

  On the other hand, when the phase determination unit 23 determines that the traveling wave voltage Vf and the reflected wave voltage Vr are not close to the same phase, that is, close to the opposite phase (step S106; No), the storage unit selection unit 34 performs the second storage. The unit 27 is selected (step S111). And the memory | storage part selection part 34 reads the control value Tc corresponding to reflection coefficient absolute value | (GAMMA) | (step S112). Then, the control value output unit 35 sets the control value Tc in the second-type matching circuit 26 (step S113). Then, the matching circuit selection unit 33 sets the switch unit 32 to the second type matching circuit 26 (step S114).

(Second impedance matching)
FIG. 30 is an example of a flowchart showing the processing procedure of the second impedance. The impedance matching device 2 repeatedly executes the process of the flowchart shown in FIG. 30 according to a predetermined cycle after executing the process of FIG.

  First, the impedance matching device 2 sets the matching state to the reference state (step S201). Specifically, the impedance matching device 2 determines the transmission system immediately after the first or second impedance matching is performed as a reference state. In the reference state, as a result of impedance matching, the reflection coefficient absolute value | Γ | is small enough to be regarded as “0”. Therefore, in the following, the reflection coefficient absolute value | Γ | in the reference state is treated as “0”.

  Next, the traveling wave / reflected wave extraction unit 21 measures the magnitudes of the traveling wave voltage Vf and the reflected wave voltage Vr (step S202). Then, the reflection coefficient calculation unit 22 calculates the reflection coefficient absolute value | Γ | (step S203). Specifically, the reflection coefficient calculation unit 22 refers to Equation (1) and calculates based on the traveling wave voltage Vf and the reflected wave voltage Vr.

  Next, the matching circuit selection unit 33 determines whether or not the reflection coefficient absolute value | Γ | is equal to or less than the threshold value | Γ | thr (step S204). Thereby, the matching circuit selection unit 33 determines whether or not impedance matching needs to be performed. Then, when the reflection coefficient absolute value | Γ | is equal to or smaller than the threshold value | Γ | thr (step S204; Yes), the matching circuit selection unit 33 determines that it is not necessary to perform impedance matching, and ends the processing of the flowchart. . On the other hand, when the reflection coefficient absolute value | Γ | is larger than the threshold value | Γ | thr (step S204; No), the matching circuit selection unit 33 determines that impedance matching needs to be performed, and proceeds to step S205. .

  Next, the phase determination unit 23 performs a second phase determination between the traveling wave voltage Vf and the reflected wave voltage Vr (step S205). Specifically, the phase determination unit 23 determines whether or not the phase of the reflected wave voltage Vr is delayed from the phase of the traveling wave voltage Vf (step S206). When the phase determination unit 23 determines that the phase of the reflected wave voltage Vr is behind the phase of the traveling wave voltage Vf (step S206; Yes), the adjustment direction determination unit 28 increases the coupling between the transmission and reception antennas. The reading direction Didx is determined as the direction (step S207). Specifically, the adjustment direction determination unit 28 determines the reading direction Didx in a direction in which an index Idx larger than the index Idx related to the control value Tc currently reflected in the matching circuit exists. Then, the adjustment step width determination unit 29 determines the step width Widx based on the reflection coefficient absolute value | Γ | (step S208). Specifically, the adjustment step width determination unit 29 refers to a predetermined map or table, for example, and sets the step width Widx to be large based on the reflection coefficient absolute value | Γ |. The above-described map and the like are created based on, for example, experiments in advance and stored in the memory of the impedance matching device 2.

  On the other hand, when the phase determination unit 23 determines that the phase of the reflected wave voltage Vr is not delayed from the phase of the traveling wave voltage Vf (step S206; No), that is, the phase of the reflected wave voltage Vr is the traveling wave voltage Vf. If it is determined that the phase is more advanced than the phase, the adjustment direction determination unit 28 determines the reading direction Didx in a direction in which the coupling between the transmission and reception antennas is weakened (step S209). Specifically, the adjustment direction determination unit 28 determines the reading direction Didx in a direction in which an index Idx smaller than the index Idx related to the control value Tc currently reflected in the matching circuit exists. Then, the adjustment step width determination unit 29 determines the step width Widx based on the reflection coefficient absolute value | Γ | (step S210). Specifically, the adjustment step width determination unit 29 refers to a predetermined map or table, for example, and sets the step width Widx to be large based on the reflection coefficient absolute value | Γ |, as in step S208.

  Next, the reading position determination unit 30 determines the storage unit and index Idx to be used (step S211). Specifically, the reading position determination unit 30 specifies a storage unit that stores the corresponding index Idx and the control value Tc related to the index Idx based on the determined reading direction Didx and step width Widx.

  Next, the control value output unit 35 reads the control value Tc and reflects the control value Tc in the matching circuit, and the matching circuit selection unit 33 appropriately switches the switch unit 32 (step S212). Specifically, when the control value Tc stored in the first storage unit 25 is used, the matching circuit selection unit 33 operates the switch unit 32 so that the first-type matching circuit 24 is enabled. Let On the other hand, when the control value Tc stored in the second storage unit 27 is used, the matching circuit selection unit 33 operates the switch unit 32 so as to select the matching circuit 26 of the second format.

  Here, a supplementary description of the flowchart of FIG. 30 will be given. The processes in steps S208 and S210 can be omitted if it is not necessary to implement them. In this case, for example, the step width Widx is fixed to “1”, for example.

  In step S211, the impedance matching device 2 may be used by switching from the first storage unit 25 to the second storage unit 27. For example, it is assumed that the impedance matching device 2 is currently using the control value Tc related to the index Idx “1” in the table of the first storage unit 25. At this time, due to a sudden change in the gap Gp, the impedance matching device 2 sets the reading direction Didx in a direction in which the coupling between the transmitting and receiving antennas is weakened, and sets the step width Widx to “4”. The selected index Idx is “−3”. Therefore, in this case, the impedance matching apparatus 2 uses the control value Tc by switching from the first storage unit 25 to the second storage unit 27. In this case, the impedance matching device 2 switches the matching circuit to be used from the first type matching circuit 24 to the second type matching circuit 26. Thus, the impedance matching device 2 can appropriately select the control value Tc by flexibly switching between the first storage unit 25 and the second storage unit 27 and using them.

Second Embodiment
Next, a second embodiment will be described. The second embodiment is different from the first embodiment in that the first type matching circuit 24 and the second type matching circuit 26 are realized by one integrated matching circuit. Hereinafter, the description of the same parts as those in the first embodiment will be omitted as appropriate.

  FIG. 31 is an example of a schematic configuration diagram of a transmission system 100A according to the second embodiment. The transmission system 100A includes a transmission circuit 1, an impedance matching device 2A, and a transmission antenna 4.

  The impedance matching device 2A includes a matching circuit 24A in which the first-type matching circuit 24 and the second-type matching circuit 26 in the first embodiment are integrated. In the matching circuit 24A, the function as the first-type matching circuit 24 and the function as the second-type matching circuit 26 are switched by switching the switch unit 32Y. In the matching circuit 24A, the control ranges of the variable inductor elements 240 and 260 used in the first type matching circuit 24 and the second type matching circuit 26, that is, the inductance correction amount Lm that can be set to these are all settable 1 Variable inductor elements. Further, the matching circuit 24A can set all the control ranges of the variable capacitor elements 241 and 261 used in the first type matching circuit 24 and the second type matching circuit 26, that is, the capacitance correction amount Cm that can be set therein. 1 variable capacitor element.

  Further, the impedance matching device 2A includes a switch unit 32X capable of selecting the through circuit 31 and the matching circuit 24A, and the configuration and second configuration of the first type matching circuit 24 when the matching circuit 24A is selected by the switch unit 32X. And a switch unit 32Y for switching the configuration of the matching circuit 26 of the type.

  As described above, in the second embodiment, the impedance matching apparatus 2A can perform impedance matching by the single matching circuit 24A by switching the switch units 32X and 32Y as in the first embodiment.

<Modification>
Next, modified examples suitable for the first embodiment and the second embodiment will be described. The modifications described below may be applied to the first embodiment and the second embodiment described above in any combination.

(Modification 1)
In the first embodiment, the impedance matching device 2 specifies the control value Tc with reference to the tables such as FIGS. 18 and 20 based on the reflection coefficient absolute value | Γ |. However, the configuration to which the present invention is applicable is not limited to this. Instead, the impedance matching device 2 may specify the control value Tc based on a value corresponding to the reflection coefficient absolute value | Γ | (hereinafter also referred to as “reflection coefficient absolute value equivalent value”). Here, the reflection coefficient absolute value equivalent value includes a reflection coefficient absolute value | Γ |, a value that is uniquely related to the reflection coefficient absolute value | Γ |, such as an absolute value of an impedance value, and other correlated values. .

  Here, a case where the control value Tc is specified based on the absolute value of the impedance value will be described. In this case, the impedance matching apparatus 2 generates a table of the quantization boundary of the absolute value of the impedance value larger than the normalized impedance (50Ω in the first embodiment) and the control value Tc as the quantization representative value as the first table. In addition to storing in the storage unit 25, a table of the quantization boundary of the absolute value of the impedance value smaller than the normalized impedance and the control value Tc serving as the quantization representative value is stored in the second storage unit 27. At this time, for example, an index Idx that is larger as the coupling coefficient k is larger is assigned to each quantization boundary and quantization representative value. Specific control values Tc stored in the first storage unit 25 and the second storage unit 27 are set in advance by calculation or experiment, for example, as in the first embodiment.

  When the impedance matching device 2 executes the first impedance matching, the impedance matching device 2 calculates the absolute value of the current impedance value, and if the absolute value of the impedance value is more than a predetermined value from the normalized impedance, The storage unit to be used is specified based on the phase determination result Jr1. Next, the impedance matching device 2 specifies the control value Tc from the specified storage unit based on the absolute value of the impedance value, and reflects the control value Tc in the matching circuit corresponding to the specified storage unit. In the second impedance matching, the impedance matching device 2 determines the reading direction Didx based on the second phase determination result Jr2 as in the first embodiment. Further, the impedance matching device 2 determines the step width Widx by referring to a predetermined table or map based on the change width of the impedance value from the matching state of the absolute value or using a predetermined fixed value. Then, the impedance matching device 2 specifies the storage unit and the index Idx to be referred to based on the reading direction Didx and the step width Widx, and reflects the corresponding control value Tc in the matching circuit corresponding to the specified storage unit.

(Modification 2)
In the first embodiment, the transmission antenna 4 and the reception antenna are modeled by a series-parallel equivalent circuit. Instead, the transmitting antenna 4 and the receiving antenna may be modeled by a series resonance equivalent circuit that is an equivalent circuit obtained by simplifying the series-parallel type equivalent circuit. Further, the input impedance trajectory Tr may be derived by being measured by experiments with the transmitting and receiving antennas actually facing each other.

(Modification 3)
The configuration of the matching circuit applicable to the present invention is not limited to the configuration shown in FIG. 1 or FIG. This will be described with reference to FIG.

  FIG. 33A shows a matching circuit in which only the variable inductor element is shared by the first-type matching circuit 24 and the second-type matching circuit 26. The matching circuit shown in FIG. 33A can function as the first-type matching circuit 24 or can function as the second-type matching circuit 26 by switching the switch unit. Similarly, the matching circuit may be configured so that only the variable capacitor element is shared by the first type matching circuit 24 and the second type matching circuit 26.

  FIG. 33B shows a circuit diagram of a matching circuit using a fixed inductor and a variable capacitor instead of the variable inductor. The matching circuit shown in FIG. 33B can function as the first-type matching circuit 24 by switching the switch unit, and can also function as the second-type matching circuit 26. The fixed inductor and the variable capacitor in FIG. 33B are examples of the “variable inductor element” in the present invention. As described above, the present invention can also be suitably implemented by the matching circuit shown in FIGS. 33 (a) and 33 (b).

(Modification 4)
In the first embodiment, the control value Tc is the inductance correction amount Lm and the capacitance correction amount Cm. However, the control value Tc to which the present invention can be applied is not limited to this.

Instead, the control value Tc corresponds to the control voltage value for reflecting the capacitance correction amount Cm applied to the variable capacitor elements 241 and 261, and the on / off of the switch group constituting the variable inductor elements 240 and 260. It may be a bit pattern for reflecting the inductance correction amount Lm. Accordingly, in this case, the impedance matching device 2 sets the capacitance correction amount Cm and the inductance correction amount Lm for setting the variable inductor elements 240 and 260 and the variable capacitor elements 241 and 261 constituting the matching circuit to predetermined capacitances and inductances. The corresponding control value Tc is stored in the first and second storage units 25 and 27 in correspondence with each reflection coefficient absolute value | Γ |.
(Modification 5)
In the first embodiment, the impedance matching device 2 includes first and second type matching circuits 24 and 26, and the gap Gp is close (that is, the coupling between the transmitting and receiving antennas is stronger than the matching point) and the gap. Impedance matching was performed in both cases where Gp is far away (ie, the coupling between the transmit and receive antennas is weaker than the matching point). However, the configuration to which the present invention is applicable is not limited to this.

  Instead, the impedance matching device 2 performs matching in the case where the gap Gp changes only in the range in which the coupling is strong from the matching point, that is, in the direction in which the gap Gp is close to the matching point. In such a case, only the matching circuit corresponding to the first type matching circuit 24 among the first and second type matching circuits 24 and 26 may be provided. FIG. 34 shows a schematic configuration of a transmission system 100B that matches the mismatch in the direction in which the gap Gp is close. The impedance matching device 2B shown in FIG. 34 mainly includes a traveling wave / reflected wave extraction unit 21, a reflection coefficient calculation unit 22, a phase determination unit 23, a matching circuit 24, a storage unit 25, and an adjustment direction determination unit. 28, an adjustment step width determination unit 29, a reading position determination unit 30, a through circuit 31, a switch unit 32, a matching circuit selection unit 33, and a control value output unit 35. The storage unit 25 corresponds to the first storage unit 25 in the first embodiment, and the matching circuit 24 corresponds to the first type matching circuit 24 in the first embodiment. Further, the variable capacitor element is connected in parallel to the transmission antenna 4 side than the variable inductor element.

  On the other hand, in the impedance matching device 2, if the gap Gp changes only in the range in which the coupling is weakened from the matching point, that is, in the range in which the gap Gp is far from the matching point, In such a case, only the matching circuit corresponding to the second type matching circuit 26 among the first and second type matching circuits 24 and 26 may be provided. FIG. 35 shows a schematic configuration of a transmission system 100C that matches mismatches in a direction in which the gap Gp is far away. The impedance matching apparatus 2B shown in FIG. 35 mainly includes a traveling wave / reflected wave extraction unit 21, a reflection coefficient calculation unit 22, a phase determination unit 23, a matching circuit 24, a storage unit 25, and an adjustment direction determination unit. 28, an adjustment step width determination unit 29, a reading position determination unit 30, a through circuit 31, a switch unit 32, a matching circuit selection unit 33, and a control value output unit 35. The storage unit 25 corresponds to the second storage unit 27 in the first embodiment, and the matching circuit 24 corresponds to the second type matching circuit 26 in the first embodiment. The variable capacitor element is connected in parallel to the transmission circuit 1 side with respect to the variable inductor element.

  The present invention is suitably applied to all wireless power transmission systems using an electromagnetic resonance coupling method. The present invention can be suitably applied to various systems such as magnetic field coupling and electric field coupling.

DESCRIPTION OF SYMBOLS 1 Transmission circuit 2, 2A Impedance matching apparatus 4 Transmitting antenna 11 Transmission signal source 12 Amplifying part 21 Traveling wave / reflected wave extraction part 22 Reflection coefficient calculation part 23 Phase determination part 24 1st type matching circuit 25 1st memory | storage part 26 Second-type matching circuit 27 Second storage unit 28 Adjustment direction determination unit 29 Adjustment step width determination unit 30 Read position determination unit 31 Through circuit 32, 32X, 32Y Switch unit 33 Matching circuit selection unit 34 Storage unit selection unit 35 Control Value output unit 100, 100A transmission system

Claims (10)

In the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, it is installed between the transmission antenna and transmission circuit, and the impedance of the transmission circuit, and the impedance of the transmitting antenna, and a matching state impedance An alignment device,
A first type matching circuit comprising: a variable inductor element inserted in series between the transmission circuit and the transmission antenna; and a variable capacitor element connected in parallel to the transmission antenna side with respect to the variable inductor element. When,
A control value corresponding to the inductance values and capacitance values required to match the predetermined impedance value with the matching circuit of the first type, is stored in advance in correspondence with the coupling coefficient between the transmit and receive antennas A first storage unit;
A second type matching circuit comprising: a variable inductor element inserted in series between the transmission circuit and the transmission antenna; and a variable capacitor element connected in parallel to the transmission circuit side with respect to the variable inductor element. When,
The inductance value required to match the predetermined impedance value with the matching circuit of the second type and the control value corresponding to the capacity stance value, the transmitting antenna and the receiving antenna and the coupling coefficient stored in advance in correspondence A second storage unit,
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that is stronger than the coupling that is in the matching state, the coupling coefficient is increased from the control value in the matching state. Determine the control value to be
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that becomes weaker than the coupling that is in the matching state, the coupling coefficient is reduced from the control value in the matching state. A control value determination unit for determining a control value to be performed;
Reads the control value by the control value determining unit has determined, the control value output unit to be reflected in the matching circuit of the first type or the second type,
An impedance matching apparatus comprising: Based on the absolute value of the reflection coefficient or the value corresponding to the absolute value of the reflection coefficient, which is a value corresponding to the absolute value, whether or not there is a need to adjust the currently used control value and the reading position of the control value is changed. The impedance matching apparatus according to claim 1, further comprising an adjustment step width determination unit that determines a step width. The control value is a change in input impedance from the transmission circuit to the transmission antenna when the transmission antenna and the reception antenna of the electromagnetic resonance coupling method are opposed to each other and the gap between the transmission antenna and the reception antenna is changed. The impedance matching device according to claim 1, wherein the impedance matching device is set based on a trajectory. 4. The impedance matching apparatus according to claim 1, wherein the control value is generated by quantization so that a loss due to reflection is always equal to or less than a predetermined threshold value. 5.   2. The control value is quantized so that a quantization interval becomes smaller as an absolute value of a reflection coefficient or a reflection coefficient absolute value equivalent value that is a value corresponding to the absolute value becomes larger. The impedance matching apparatus as described in any one of thru | or 4. In the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, it is installed between the transmission antenna and transmission circuit, and the impedance of the transmission circuit, and the impedance of the transmitting antenna, and a matching state impedance An alignment device,
A first type matching circuit comprising: a variable inductor element inserted in series between the transmission circuit and the transmission antenna; and a variable capacitor element connected in parallel to the transmission antenna side with respect to the variable inductor element. When,
A control value corresponding to the inductance values and capacitance values required to match the predetermined impedance value with the matching circuit of the first type, is stored in advance in correspondence with the coupling coefficient between the transmit and receive antennas A first storage unit;
A second type matching circuit comprising: a variable inductor element inserted in series between the transmission circuit and the transmission antenna; and a variable capacitor element connected in parallel to the transmission circuit side with respect to the variable inductor element. When,
The inductance value required to match the predetermined impedance value with the matching circuit of the second type and the control value corresponding to the capacity stance value, the transmitting antenna and the receiving antenna and the coupling coefficient stored in advance in correspondence A control method executed by an impedance matching device comprising:
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that is stronger than the coupling that is in the matching state, the coupling coefficient is increased from the control value in the matching state. Determine the control value to be
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that becomes weaker than the coupling that is in the matching state, the coupling coefficient is reduced from the control value in the matching state. A control value determining step for determining a control value to be performed;
Reads the control value by the control value determining step has determined, the control value output step to be reflected in the matching circuit of the first type or the second type,
A control method characterized by comprising: In the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, it is installed between the transmission antenna and transmission circuit, and the impedance of the transmission circuit, and the impedance of the transmitting antenna, and a matching state impedance An alignment device,
A matching circuit comprising: a variable inductor element inserted in series between the transmission circuit and the transmission antenna; and a variable capacitor element connected in parallel to the transmission antenna side with respect to the variable inductor element;
A control value corresponding to the inductance values and capacitance values required to match the predetermined impedance value using the matching circuit, the transmitting antenna and storage section in correspondence with the coupling coefficient is stored in advance in a receiving antenna ,
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that is stronger than the coupling that is in the matching state, the coupling coefficient is increased from the control value in the matching state. Determine the control value to be
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that becomes weaker than the coupling that is in the matching state, the coupling coefficient is reduced from the control value in the matching state. A control value determination unit for determining a control value to be performed;
Reads the control value by the control value determining unit has determined, the control value output unit to be reflected in the matching circuit,
An impedance matching apparatus comprising: In the wireless power transmission system for transmitting power from the transmitting antenna to the receiving antenna, it is installed between the transmission antenna and transmission circuit, and the impedance of the transmission circuit, and the impedance of the transmitting antenna, and a matching state impedance An alignment device,
A variable inductor element inserted in series between the transmission circuit and the transmission antenna; a variable capacitor element connected in parallel to the transmission circuit side relative to the variable inductor element;
A matching circuit comprising:
A control value corresponding to the inductance values and capacitance values required to match the predetermined impedance value using the matching circuit, the transmitting antenna and storage section in correspondence with the coupling coefficient is stored in advance in a receiving antenna ,
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that is stronger than the coupling that is in the matching state, the coupling coefficient is increased from the control value in the matching state. Determine the control value to be
When it is determined that the coupling between the transmitting antenna and the receiving antenna is shifted in a direction that becomes weaker than the coupling that is in the matching state, the coupling coefficient is reduced from the control value in the matching state. A control value determination unit for determining a control value to be performed;
Reads the control value by the control value determining unit has determined, the control value output unit to be reflected in the matching circuit,
An impedance matching apparatus comprising: Based on the absolute value of the reflection coefficient or the value corresponding to the absolute value of the reflection coefficient, which is a value corresponding to the absolute value, whether or not there is a need to adjust the currently used control value and the reading position of the control value is changed. impedance matching device according to claim 7 or 8, further comprising an adjustment step width determination unit which determines the step size. The control value is a change in input impedance from the transmission circuit to the transmission antenna when the transmission antenna and the reception antenna of the electromagnetic resonance coupling method are opposed to each other and the gap between the transmission antenna and the reception antenna is changed. The impedance matching device according to claim 7 , wherein the impedance matching device is set based on a trajectory.

Images