WO2019103134A1 - Impedance matching circuit - Google Patents

Abstract

[Problem] To provide an impedance matching circuit capable of being used for a high-power application of several tens of watts or more, and capable of higher-speed impedance matching. [Solution] An impedance matching circuit provided with a variable frequency alternating-current power source is connected to a desired object load, the frequency of the variable frequency alternating-current power source is changed, the trajectory of an output impedance is represented in a spiral form on a Smith chart, and the output impedance is either matched to an impedance being the complex conjugate of the impedance of the object load, or is brought into a desired numerical range. Furthermore, a plurality of frequency ranges in which the output impedance is either matched to the impedance being the complex conjugate of the impedance of the object load, or is brought into the desired numerical range are caused to exist. It is preferable that the impedance being the complex conjugate of the impedance of the object load be plotted in a predetermined place within the whole range on the Smith chart, and that the frequency range in which the frequency of the variable frequency alternating-current power source is changed be a desired frequency range.

Description

Impedance matching circuit

The present invention relates to an impedance matching circuit.

In recent years, semiconductor technology such as GaN HEMT (High Electron Mobility Transistor) using GaN has been developed, and a microwave power generator (AC power source) has been developed using these semiconductors.

Applications of such microwave power generators include microwave surgical equipment. In surgery with a microwave surgical device, the affected area is heated by microwaves. However, as the operation progresses, the condition of the affected area changes, and the impedance as a load on the affected area seen from the microwave generator changes. In addition, organs and blood vessels that are affected areas have different impedances depending on the site.

A device that matches the impedance on the microwave generator side immediately during surgery to prevent power reflection and efficiently transmit power to the load when the impedance changes depending on the progress of the operation and the site. And circuits are required.

Examples of impedance matching devices include a slug tuner and a stub tuner (for example, see Patent Document 1 as an example of a stub tuner). Further, an impedance matching circuit using a varactor diode or an FET switch has also been proposed (for example, see Patent Document 2 as an example of an impedance matching circuit configured by a varactor diode).

Japanese Patent Application Laid-Open No. 10-150306 JP 2011-237335 A

However, since the slug tuner, the stub tuner, etc. perform mechanical alignment, it takes about 100 milliseconds for alignment.

On the other hand, in a circuit using a varactor diode or the like, the time required for matching is relatively short. However, since the power resistance of the circuit element is as low as 1.0 W or less, it can not be used for high power applications of several tens W or more such as microwave surgical equipment.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an impedance matching circuit that can be used for high power applications of several tens of W or more and that can perform higher-speed impedance matching.

The problems are solved by the present invention described below. That is, the impedance matching circuit according to the present invention includes a variable frequency AC power source and is connected to a desired target load, changes the frequency of the variable frequency AC power source, and displays the locus of output impedance spirally on a Smith chart. And an impedance that is a complex conjugate of the impedance of the target load, and the output impedance is made to match or fall within a desired numerical range.

According to the impedance matching circuit according to the present invention, by changing the frequency of the variable frequency AC power source, the output impedance can be matched against the impedance indicated by the desired target load at a high speed such as 1.0 millisecond or less immediately. It is possible to

Furthermore, the impedance matching circuit can be configured without using a variable reactance element such as a varactor diode. That is, the impedance matching circuit can be configured only with a circuit element having high resistance to high power. Thus, it can be used for high power applications of several tens of watts or more.

FIG. 5 is a circuit diagram of a system comprising a fixed frequency AC power source V and a desired target load exhibiting an impedance ZL. FIG. 5 is a circuit diagram in which an impedance matching circuit having a fixed impedance circuit is connected between a fixed frequency AC power source V and a load. It is the circuit diagram which connected the impedance matching circuit provided with the variable element between fixed frequency alternating current power source V and load. It is a circuit diagram showing typically the principle and the embodiment of the impedance matching circuit concerning the present invention. It is a circuit diagram showing Example 1 of the impedance matching circuit concerning the present invention. In Example 1, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 1, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. FIG. 6 is a Smith chart in which the impedance of 10 random loads is plotted as an example of the impedance indicated by the load when FIG. 5 is broken by a broken line (3) and the load side (right side in FIG. 5) is seen . FIG. 7 is a Smith chart in which the 10 complex conjugate points of FIG. 8 are superimposed and plotted. FIG. 5 is a graph of a reflection coefficient γ iii and a desired frequency band when the load side (right side in FIG. 5) is seen by cutting FIG. 5 with a broken line (3). It is a circuit diagram showing Example 2 of the impedance matching circuit concerning the present invention. In Example 2, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 2, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. FIG. 11 is a graph of a reflection coefficient γiii and a desired frequency band when the load side (right side in FIG. 11) is seen by cutting FIG. 11 with a broken line (3). It is a circuit diagram showing Example 3 of an impedance matching circuit concerning the present invention. In Example 3, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 3, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. FIG. 15 is a graph of a reflection coefficient γ iii and a desired frequency band when the load side (right side in FIG. 15) is seen by cutting FIG. 15 with a broken line (3). It is a circuit diagram showing Example 4 of the impedance matching circuit concerning the present invention. In Example 4, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 4, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. FIG. 19 is a graph of a reflection coefficient γiii and a desired frequency band when the load side (right side in FIG. 19) is seen by cutting FIG. 19 with a broken line (3). It is a circuit diagram showing Example 5 of the impedance matching circuit concerning the present invention. In Example 5, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 5, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. FIG. 18 is a graph of a reflection coefficient γ iii and a desired frequency band when the load side (right side in FIG. 18) is seen by cutting FIG. 18 with a broken line (3). It is a circuit diagram showing Example 6 of the impedance matching circuit concerning the present invention. It is a circuit diagram showing Example 7 of an impedance matching circuit concerning the present invention. It is a circuit diagram showing Example 8 of the impedance matching circuit concerning the present invention. In Example 6, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 6, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. 27 is a graph of a reflection coefficient γiii and a desired frequency band when the load side (right side in FIG. 27) is seen by cutting FIG. 27 by a broken line (3). In Example 7, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 7, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. FIG. 28 is a graph of a reflection coefficient γiii and a desired frequency band when the load side (right side in FIG. 28) is seen by cutting FIG. 28 by a broken line (3). In Example 8, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within the desired frequency band, and plotted Zi. In Example 8, it is a Smith chart which changed the frequency of variable frequency alternating current power source Vs within a desired frequency band, and plotted Zii. 29 is a graph of a reflection coefficient γiii and a desired frequency band when the load side (right side in FIG. 29) is seen by cutting FIG. 29 by a broken line (3).

The first feature of the present embodiment includes a variable frequency AC power source and is connected to a desired target load, changes the frequency of the variable frequency AC power source, and spirals the locus of the output impedance on the Smith chart. And an impedance matching circuit that matches the output impedance with the impedance that is the complex conjugate of the impedance of the target load or that falls within a desired numerical range.

According to this configuration, by changing the frequency of the variable frequency AC power source, it is possible to match the output impedance to the impedance indicated by the desired target load at a high speed and immediately below 1.0 millisecond. Become. Furthermore, the impedance matching circuit can be configured only with a circuit element having high resistance to high power, and can be used for high power applications of several tens of W or more.

In the present invention, matching refers to matching the output impedance to a value that is a complex conjugate of the impedance of the target load or within a desired numerical range.

Further, in the present invention, the variable frequency alternating current power source is an alternating current power source whose frequency can be changed.

The second feature is that the impedance matching circuit has a plurality of frequency ranges in which the output impedance matches or falls within a desired numerical range with respect to the impedance that is the complex conjugate of the impedance of the target load.

According to this configuration, in addition to the above-mentioned effects, it is possible to more reliably perform high-speed and immediate output impedance matching.

The third feature is that the impedance matching circuit is configured such that an impedance that is a complex conjugate of the impedance of the target load is plotted at a predetermined location on the entire range on the Smith chart.

According to this configuration, in addition to the above-described effects, impedance that is complex conjugate is plotted according to the impedance of the target load over the entire range on the Smith chart. Therefore, by expressing the locus of the spiral output impedance on the Smith chart, it is possible to match the output impedance to the complex conjugate impedance or to fall within the desired numerical range over the entire range on the Smith chart. It becomes.

A fourth feature is that the frequency range for changing the frequency of the variable frequency alternating current power source is an impedance matching circuit that is a desired frequency range.

According to this configuration, in addition to the above effects, output impedance matching can be performed in a frequency range corresponding to the application of the impedance matching circuit.

A fifth feature is that the impedance matching circuit includes at least one transmission line.

According to this configuration, in addition to the above effects, by providing the transmission line, the transfer efficiency of power from the variable frequency AC power source can be improved, and the internal heat generation loss of the matching circuit can be reduced. Furthermore, the frequency range for changing the frequency of the variable frequency AC power source can be set to a high frequency range, and design and trial manufacture of the impedance matching circuit in the high frequency range can be facilitated.

A sixth feature is that the impedance matching circuit includes at least one coupled line.

According to this configuration, in addition to the above effects, the impedance matching circuit can be miniaturized.

A seventh feature is that the impedance matching circuit includes at least one lumped constant element.

According to this configuration, in addition to the above effects, the impedance matching circuit can be miniaturized, and the design of the impedance matching circuit is facilitated.

Hereinafter, the principle and the embodiment of the impedance matching circuit according to the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows a circuit diagram of a system of fixed frequency AC power source V with an impedance of 50 ohms and a desired target showing an impedance ZL. There is a need to efficiently transfer power from the fixed frequency AC power source V to the desired object without reflection.

The reflection coefficient γ is (ZL−50) / (ZL + 50) when looking from the broken line (1) in FIG. 1 to the left in the drawing. In FIG. 1, when the impedance ZL of the load is 50Ω, which is the same as the impedance of the fixed frequency AC power source V, the power from the fixed frequency AC power source V is transmitted to the load without reflection. When the load impedance ZL changes, the reflection coefficient γ becomes less than 1 and the power is reflected, and only the remaining non-reflected power is transmitted to the load.

However, when the load is constant and the impedance of the fixed frequency AC power source V and the load is different, as shown in FIG. 2, an impedance matching circuit 1 having a fixed impedance circuit is inserted between the fixed frequency AC power source V and the load. In this way, it is possible to prevent the reflection and transfer the power to the desired object. However, in an actual application, it is assumed that the impedance ZL of the load changes, and the matching state also deviates as the impedance of the load changes.

Therefore, as a countermeasure, as shown in FIG. 3, the impedance matching circuit 2 provided with a variable element is connected between the fixed frequency AC power source V and the load, and the output impedance of the impedance matching circuit 2 is adjusted. There is a means to get in line with the Examples of variable elements include a slug tuner, a stub tuner, and a varactor diode. However, in the case of the slag tuner, the stub tuner, etc., there is a problem that it takes about 100 milliseconds for alignment because of mechanical alignment.

On the other hand, in matching circuits using varactor diodes, although the matching variable speed is fast, the milliwatt class whose power resistance of the element is 1.0 W or less makes it possible to use for high power (several tens of W class) high power applications. It was impossible.

Therefore, in the present invention, as shown in FIG. 4, the variable frequency AC power source Vs is used in place of the fixed frequency AC power source V, and the frequency of the variable frequency AC power source Vs is changed to Align. The impedance of the variable frequency AC power source Vs is, for example, 50Ω.

More specifically, as shown in FIG. 4, the impedance matching circuit 3 includes a variable frequency AC power source Vs and is connected to a desired target load. Furthermore, while connected to a desired target load, the frequency of the variable frequency AC power source Vs is changed to make the locus of the output impedance appear spirally on the Smith chart, resulting in a complex conjugate of the impedance ZL of the target load With respect to the impedance, the output impedance matches or falls within a desired numerical range.

The variable frequency AC power source Vs is an AC power source capable of changing the frequency.

When the load impedance ZL changes, it appears as a trace on the Smith chart. In FIG. 4, since the impedance of the variable frequency AC power source Vs is 50Ω, it is normalized to 50Ω to be 1 and plotted so that the origin (center) is 1.

If all applications are assumed, it is ideal that the frequency locus of the impedance seen from the broken line (1) to the left in FIG. 4 covers the inside of the unit circle on the Smith chart without any gap.

However, it is impossible in practice to completely cover the frequency locus without gaps in the unit circle. Therefore, in the present invention, the output impedance matches or has a desired numerical range with respect to the impedance that is the complex conjugate of the impedance ZL of the target load at all points within the unit circle, with the origin of the unit circle of the Smith chart as the starting point. Consider an impedance matching circuit that draws a trajectory that fits inside. Therefore, even if the impedance ZL indicated by the load changes, it is possible to reduce the reflection at a frequency corresponding to a point coincident with or close to the spiral locus by giving a frequency that is complex conjugate matched each time.

In the above-mentioned desired numerical range in the present invention, the input side reflection coefficient (b1 / a1) which is the ratio of the incident wave a1 to the reflected wave b1 to the impedance matching circuit 1 is a desired dB (decibel) value It shall match to the following (as an example, -10 dB or less). Conversion to dB value is −20 × log (reflection coefficient). Hereinafter, the input-side reflection coefficient (b1 / a1) is denoted as (b1 / a1) as necessary. The incident wave a1 is the power incident on the output impedance. The reflected wave b1 is the power reflected from the output impedance. Furthermore, the "input side" of (b1 / a1) refers to the input side in the output impedance.

Further, in the present invention, matching means that the output impedance matches the impedance which is the complex conjugate of the impedance ZL of the target load or falls within a desired numerical range.

According to the impedance matching circuit 3 according to the present invention, by changing the frequency of the variable frequency AC power source Vs, an output can be made to the impedance ZL indicated by the desired target load at a high speed of 1.0 millisecond or less immediately. It is possible to match the impedance.

Furthermore, the impedance matching circuit 3 can be configured without using a variable reactance element such as a varactor diode. That is, the impedance matching circuit 3 can be configured only with a circuit element having high resistance to high power. Thus, it can be used for high power applications of several tens of watts or more.

More preferably, there are a plurality of frequency ranges in which the output impedance matches or falls within a desired numerical range with respect to the impedance that is the complex conjugate of the impedance ZL of the target load. According to such an impedance matching circuit, in addition to the above effects, it is possible to more reliably perform high-speed and immediate output impedance matching.

More preferably, an impedance which is a complex conjugate of the impedance ZL of the target load is plotted at a predetermined position on the entire surface of the Smith chart. According to such an impedance matching circuit, in addition to the above effects, an impedance which is complex conjugate in accordance with the impedance ZL of the target load is plotted over the entire range on the Smith chart. Therefore, by expressing the locus of the spiral output impedance on the Smith chart, it is possible to match the output impedance to the complex conjugate impedance or to fall within the desired numerical range over the entire range on the Smith chart. It becomes.

More preferably, the frequency range for changing the frequency of the variable frequency AC power source Vs is a desired frequency range. According to such an impedance matching circuit, in addition to the above effects, it is possible to match the output impedance in the frequency range according to the application of the impedance matching circuit.

The (b1 / a1) of -10 dB means that the reflected wave is 1/10 of the incident wave. Therefore, (b1 / a1) is also 1/10.

Although each Example concerning the embodiment of the present invention is explained below, the present invention is not limited only to the following examples. The same reference numerals as in FIG. 4 denote the same parts as in FIG. 4, and redundant descriptions will be omitted or simplified.

Example 1
A circuit diagram showing the impedance matching circuit of the first embodiment is shown in FIG. FIG. 5 shows a circuit diagram using two different transmission lines a and b as the output impedance shown by the impedance matching circuit including the variable frequency AC power source Vs. The transmission lines a and b are electrically connected in series.

For example, the impedance and physical length of the two transmission lines a and b are Zc ^a (Ω) and La (mm), and Zc ^b (Ω) and Lb (mm), respectively. The impedance of the variable frequency AC power source Vs is 50Ω. According to the frequency of such a variable frequency AC power source Vs, the output impedance consisting of the two transmission lines a and b appears a spiral trajectory on the Smith chart.

At least one of the two transmission lines a and b, which are output impedances, is a transmission line with a physical length of 4000 mm having an impedance of 50 Ω and is electrically connected in series to a desired object. In the embodiment of FIG. 5, the transmission line b is a transmission line of physical length Lb 4000 mm having an impedance Zc ^b of 50 Ω.

The impedance Zi and the reflection coefficient γi as viewed from the variable frequency AC power source Vs side (left side in FIG. 5) by cutting FIG. 5 with a broken line (2) are as follows:

It becomes. Here, φa = La × 2 / λ, where λ is the wavelength (mm) on the transmission line a.

Zc ^a and La are determined such that the imaginary part of Zi becomes 0Ω at the lower limit of the desired frequency band, and γi becomes the target maximum reflection coefficient at the upper limit of the same frequency band. For example, assuming an IMS (Industry Science Medical) band as a desired frequency band for changing the frequency of the variable frequency AC power source Vs, assuming that the lower limit frequency is 2.4 GHz, the upper limit frequency is 2.5 GHz, and the target maximum reflection coefficient is 0.8, Zc ^a It will be 15 Ω, La 285 mm. These values are substituted into Equation 1, and the frequency of the variable frequency AC power source Vs is changed within a desired frequency band and plotted on a Smith chart, which is shown in FIG. As shown in FIG. 6, it becomes a frequency locus going outward from the origin.

Next, the impedance Zii (output impedance) as viewed from the variable frequency AC power source Vs side (left side in FIG. 5) by cutting FIG.

It becomes. However, it is φb = Lb × 2 / λ, Lb is 4000 mm, Zc ^b is 50 [Omega, lambda is the wavelength on the transmission line b (mm).

These values are substituted into Equation 5, and the frequency of the variable frequency AC power source Vs is changed within a desired frequency band, and Zii is plotted on a Smith chart as shown in FIG. When plotted on a Smith chart, a spiral trajectory is obtained as shown in FIG. Here, the complex conjugate of the impedance Zii and the impedance ZL of the load is

It is perfectly aligned if it If it deviates from the equation 8, reflection occurs at the broken line (1). The reflection coefficient γii is

It is.

Also, assuming that the two transmission lines a and b are lossless,

It becomes. The reflection coefficient is γiii when reflection occurs in the broken line (3) in FIG. 5, and the reflection coefficient when the load side (right side in FIG. 5) is seen in the broken line (3). That is, the reflection coefficient γ iii is the input-side reflection coefficient (b1 / a1) which is the ratio of the incident wave a1 to the impedance matching circuit and the reflected wave b1.

On the other hand, random 10 points shown on the Smith chart of FIG. 8 as an example of the impedance ZL which a load shows when FIG. 5 is cut off with a broken line (3) and the load side (right side in FIG. 5) is seen. Consider the impedance of (Z _L01 to Z _L10 ). The ten points of impedance randomly give an arbitrary impedance of the target load so as to be scattered sparsely within the Smith chart circle. These ten points are obtained by plotting the impedance that is the complex conjugate of the impedance ZL of the target load at each predetermined position over the entire range on the Smith chart.

A Smith chart in which 10 complex conjugate points (Z ^* _L01 to Z ^* _L10 ) in FIG. 8 are plotted is shown in FIG. 9 (the 10 points in FIG. 8 are vertically inverted). Furthermore, the spiral trajectory shown in FIG. 7 is superimposed on FIG. The reflection is minimized at the frequency corresponding to the point closest to the spiral trajectory from each plot point in FIG. What made the situation graph on a frequency axis is shown in FIG. Each curve of the graph of FIG. 10 is the reflection coefficient γ iii for each plot point of FIG.

In this way, the frequency of the variable frequency AC power source Vs is changed to make the locus of the output impedance appear spirally on the Smith chart, and the output impedance matches the impedance that is the complex conjugate of the impedance ZL of the target load. Or within the desired numerical range.

As shown in FIG. 7 and FIG. 9, by expressing the locus of the spiral output impedance on the Smith chart, impedance (Z ^* _L01 to Z ^* _L10 ) which becomes complex conjugate over the entire range on the Smith chart. Whereas the output impedance can be matched or within the desired numerical range.

The minimum value of each curve in FIG. 10 is indicated by a black dot. This is the optimum frequency (the frequency at which the reflection coefficient γiii is minimum) for each load (the impedance Z _L01 to Z _{L10 of the} 10 points) given at random. In the present invention, when the desired frequency band for changing the frequency of the variable frequency AC power source Vs is the IMS band, it is desirable to set the output impedance to -10 dB or less with respect to the impedance that is the complex conjugate of the impedance ZL of the target load. To be within the numerical range of By setting the desired numerical range to -10 dB or less, in the case of FIG. 10, the reflection coefficient γiii becomes -10 dB or less at all loads (randomly given 10 points of impedance Z _L01 to Z _L10 ) It can be seen that there is more than one frequency. That is, it can be understood that a plurality of frequency ranges in which (b1 / a1) becomes −10 dB or less exist in a desired frequency band (2.4 GHz or more and 2.5 GHz or less). Therefore, in the impedance matching circuit of the present embodiment, a plurality of frequency ranges in which the output impedance matches or falls within a desired numerical range for the impedance which is the complex conjugate of the impedance ZL of the target load are present. According to the above, it is possible to perform high-speed and immediate output impedance matching more reliably.

When the impedances (Z ^* _L01 to Z ^* _L10 ) at 10 points in FIG. 9 are plotted on a spiral trajectory, the output impedance is not the impedance that is the complex conjugate of the impedance ZL of the target load. Matched and matched. In the first embodiment, it can be seen from FIG. 9 that although there is no coincidence at all ten points, there is a frequency which is within the desired numerical range and is −10 dB or less. Of course, depending on the settings of the 10 points of impedance (Z ^* _L01 to Z ^* _L10 ), there are multiple matching impedances, and the output impedance is in multiple frequency ranges with respect to the impedance that becomes the complex conjugate of the impedance ZL of the target load. There is also a possibility of a match.

Furthermore, according to the impedance matching circuit according to the first embodiment, in addition to the effects of the embodiment shown in FIG. 4, by providing at least one transmission line b, the power from the variable frequency AC power source Vs can be The transfer efficiency is improved, and the internal heat generation loss of the impedance matching circuit can be reduced. Furthermore, the frequency range for changing the frequency of the variable frequency AC power source Vs can be set to a high frequency range (for example, several GHz band or more), and design and trial manufacture of the impedance matching circuit in the high frequency range becomes easy.

(Example 2)
Next, the impedance matching circuit according to the second embodiment will be described with reference to FIGS. The same reference numerals as in FIG. 4 and the first embodiment denote the same parts, and a redundant description will be omitted or simplified.

The first embodiment comprises a transmission line a having an impedance Zc ^a of 15 Ω and a transmission line b having an impedance Zc ^b of 50 Ω. Coaxial cables having an impedance of 50Ω are commercially available. On the other hand, the transmission line of Zc ^a 15 Ω and La 285 mm is assumed to be difficult to obtain. Thus, an example in which a coaxial cable with an impedance of 15 Ω is not used will be described in a second embodiment.

The impedance matching circuit of the second embodiment is shown in FIG. The impedance of the variable frequency AC power source Vs is 50 Ω as in the first embodiment. The impedance Zi seen from the side of the variable frequency AC power source Vs (left side in FIG. 11) by cutting FIG.

It becomes. The reflection coefficient γi is the same as the equation (4).

The inductor L and the capacitor C are determined such that the imaginary part of Zi becomes 0Ω at the lower limit of the desired frequency band, and γi becomes the target maximum reflection coefficient at the upper limit of the same frequency band. For example, assuming the IMS band as the desired frequency band as in the first embodiment, assuming that the lower limit frequency is 2.4 GHz, the upper limit frequency is 2.5 GHz, and the target maximum reflection coefficient is 0.8, L 101 nH and C 0.04 pF are obtained. These values are substituted into Equation 11, and the frequency of the variable frequency alternating current power source Vs is changed within a desired frequency band and plotted on a Smith chart as shown in FIG. As shown in FIG. 12, it becomes a frequency locus going outward from the origin.

Next, the impedance Zii (output impedance) as viewed from the variable frequency AC power source Vs side (left side in FIG. 11) by cutting FIG. 11 along the broken line (1) is expressed by Equations 5 to 7.

These values are substituted into Equation 5, and the frequency of the variable frequency AC power source Vs is changed within a desired frequency band, and Zii is plotted on a Smith chart as shown in FIG. When plotted on a Smith chart, a spiral trajectory is obtained as shown in FIG.

Assuming that the impedance matching circuit shown in FIG. 11 is lossless, several 10 is obtained (see also several 9). Similar to Embodiment 1 and FIG. 8, the impedance of 10 points is randomly given sparsely within the Smith chart circle, and the reflection coefficient γiii when reflection occurs at the broken line (3) of FIG. 11 is shown in FIG. It can be seen from FIG. 14 that at all loads, there are one or more frequencies at which the reflection coefficient γiii is −10 dB or less.

According to the impedance matching circuit of the second embodiment, in addition to the effects of the embodiment shown in FIG. 4 and the first embodiment, the impedance matching can be achieved by providing at least one lumped constant element (L or C). The circuit can be miniaturized and the design of the impedance matching circuit is facilitated.

(Example 3)
Next, the impedance matching circuit according to the third embodiment will be described with reference to FIGS. The same reference numerals as in FIG. 4 and the first embodiment or the second embodiment denote the same parts or parts, and a redundant description will be omitted or simplified.

In the third embodiment shown in FIG. 15, as an impedance matching circuit provided with a variable frequency AC power source Vs, two different transmission lines b and c and the same electrostatics on the left end side of each of the transmission lines b and c It comprises two capacitors C1 and C1 having a capacitance. A capacitor on the variable frequency AC power source Vs side is C1, and a capacitor on the desired target side, which is a load, is C2.

The impedance Zi is derived by cutting along the broken line (2) in FIG. 15 and looking at the variable frequency AC power source Vs side (left side in FIG. 15). First, the impedance Z ₁ of the variable frequency AC power source Vs and C1 is

It becomes. Furthermore, impedance Z ₂ with transmission line c added to the right is

It becomes. Z ₁₁ is the impedance Zc ^c Omega transmission line c, a coefficient obtained by dividing by (jtanΦc). Φ c is the physical length L c (mm) × 2 / λ of the transmission line c (λ is the wavelength (mm) on the transmission line c). Z ₁₂ and Z ₂₁ together with Zc ^c Omega, a coefficient obtained by dividing by (jsinΦc).

Therefore,

It becomes. γ i is the same as in Eq.

As in the first embodiment, in the transmission lines b and c and the two C1 and C2, the imaginary part of Zi becomes 0 Ω at the lower limit of the desired frequency band, and γi becomes the target maximum reflection coefficient at the upper limit of the same frequency band. As determined. Assuming an IMS band as a desired frequency band as in Example 1, assuming that the lower limit frequency is 2.4 GHz, the upper limit frequency is 2.5 GHz, and the target maximum reflection coefficient is 0.8, C1 = C2 = 0.5 pF, Zc ^c 15 Ω, Lc 173 It becomes deg (2.45 GHz).

When Zi in equation 14 is plotted on a Smith chart, it becomes a frequency locus going outward from the origin as shown in FIG.

Next, when the impedance Zii (output impedance) is obtained by cutting the broken line (1) in FIG. 15 and looking at the variable frequency AC power source Vs side (left side in FIG. 15), several 5 to several 7 are obtained. . When the frequency of the variable frequency AC power source Vs is changed within a desired frequency band and Zii of the equation 5 is plotted on a Smith chart, a spiral trajectory is obtained as shown in FIG.

Assuming that the impedance matching circuit shown in FIG. 15 is lossless, several 10 can be obtained (see also several 9). Similar to the first embodiment and FIG. 8, the impedance of 10 points is randomly given sparsely within the Smith chart circle, and the reflection coefficient γ iii when the reflection occurs at the broken line (3) of FIG. 15 is shown in FIG. It can be seen from FIG. 18 that at all loads, there are one or more frequencies at which the reflection coefficient γiii is −10 dB or less.

Furthermore, as a result of trial manufacture of the impedance matching circuit of FIG. 15 by the applicant and verification, it was confirmed that the substrate fits within about 25 mm in width and about 40 mm in depth using a substrate with a relative dielectric constant of about 3 and a thickness of 1 mm or less. .

Furthermore, according to the impedance matching circuit according to the third embodiment, in addition to the effects of the embodiment shown in FIG. 4 and the first embodiment, the impedance can be improved by providing at least one lumped constant element (C1 or C2). The matching circuit can be miniaturized, and the design of the impedance matching circuit is facilitated.

(Example 4, Example 5)
Next, the impedance matching circuit of the fourth embodiment will be described with reference to FIGS. 19 to 22. FIG. An impedance matching circuit according to a fifth embodiment of the present invention will be described with reference to FIGS. 23 to 26. The same reference numerals as in FIG. 4 and the above-described embodiments denote the same parts, and a redundant description will be omitted or simplified.

From FIG. 19, an impedance matching circuit including a capacitor C 3, transmission lines b and d, and a coupling line CL is taken as Example 4 as an impedance matching circuit including a variable frequency alternating current power source Vs. On the other hand, referring to FIG. 23, as an impedance matching circuit provided with a variable frequency alternating current power source Vs, an impedance matching circuit constituted only by a transmission line b and two coupled lines CL1 and CL2 is taken as Example 5. In Example 4 and Example 5, Zi was determined by circuit simulation so that the imaginary part of Zi becomes 0 Ω at the upper limit of the desired frequency band and γi becomes the target maximum reflection coefficient at the lower limit of the same frequency band. . That is, the relationship between the upper limit and the lower limit of the desired frequency band is reversed between the first embodiment and the third embodiment. Also in the fourth and fifth embodiments, an IMS band is considered as a desired frequency band. Therefore, in Example 4 and Example 5, the upper limit frequency is 2.4 GHz and the lower limit frequency is 2.5 GHz.

Further, in the fourth embodiment, the target maximum reflection coefficient is 0.7. In this case, the C3 is 3.8 pF, the impedance Zc ^d of the transmission line d is 41Omu, Ld is 157deg (2.45GHz), the coupling line CL is even mode impedance Zeven 87Omu, odd mode impedance Zodd 44Ω, L 119deg (2.45GHz) . As shown in FIG. 20, Zi has a locus going outward from the origin on the Smith chart. However, the origin is the upper limit frequency, and the lower limit frequency is on the unit circle side of the Smith chart.

Next, when the impedance Zii (output impedance) as viewed from the side of the variable frequency AC power source Vs (left side in FIG. 19) cut along the broken line (1) in FIG. 19 is plotted on the Smith chart, FIG. As shown, it has a spiral trajectory.

Similar to Embodiment 1 and FIG. 8, impedances of 10 points are randomly given sparsely within the Smith chart circle, and a reflection coefficient γiii when reflection occurs at the broken line (3) of FIG. 19 is shown in FIG. It can be seen from FIG. 22 that at all the loads, there are one or more frequencies at which the reflection coefficient γiii is −10 dB or less.

On the other hand, in the fifth embodiment, the target maximum reflection coefficient is 0.9. In this case, the coupling line CL1 on the variable frequency AC power source Vs side of the impedance matching circuit shown in FIG. 23 is 57.65 Ω for Zeven1, 40.4 Ω for Zodd1, and L 96 deg (2.45 GHz), and the coupling line CL2 for the load side is 57.65 for Zeven2. Ω, Zodd2 becomes 40.4 Ω, L 80.5 deg (2.45 GHz).

When impedance Zi cut on broken line (2) in FIG. 23 and looking at variable frequency AC power source Vs side (left side in FIG. 23) is plotted on a Smith chart, as shown in FIG. It becomes a locus. However, as in the fourth embodiment, the origin is the upper limit frequency, and the lower limit frequency is on the unit circle side of the Smith chart.

Next, when the impedance Zii (output impedance) as cut at the broken line (1) in FIG. 23 and looking at the variable frequency AC power source Vs side (left side in FIG. 23) is plotted on a Smith chart, FIG. As shown, it has a spiral trajectory.

Similar to Embodiment 1 and FIG. 8, impedances of 10 points are randomly given sparsely within the Smith chart circle, and a reflection coefficient γiii when reflection occurs at the broken line (3) of FIG. 23 is shown in FIG. It can be seen from FIG. 26 that at all loads, there are one or more frequencies at which the reflection coefficient γiii is −10 dB or less.

According to the impedance matching circuits according to the fourth and fifth embodiments, in addition to the effects of the embodiment shown in FIG. 4 and the first embodiment, at least one coupled line (CL, CL1, CL2) is provided. The impedance matching circuit can be miniaturized.

Further, according to the impedance matching circuit according to the fourth embodiment, in addition to the effects of the embodiment shown in FIG. 4 and the first embodiment, the impedance matching circuit can be provided by including at least one lumped constant element (C3). Can be miniaturized and the design of the impedance matching circuit is facilitated.

(Example 6, Example 7, Example 8)
The impedance matching circuits of the sixth to eighth embodiments will now be described with reference to FIGS. The same reference numerals as in FIG. 4 and the above-described embodiments denote the same parts, and a redundant description will be omitted or simplified. Also in the sixth to eighth embodiments, the IMS frequency band is considered as the desired frequency band.

As described in the first to fifth embodiments, as the circuit diagrams (FIGS. 5, 11, 15, 19, and 23) of each embodiment, the output impedance that draws an arc from the origin to the outside, and the impedance Zc ^b Exemplifies a circuit diagram in which a transmission line b having 50 Ω is connected. In the Smith chart of each embodiment, a spiral trajectory of frequency can be realized. The output impedance that arcs outward from this origin is also using the steepness of the passband and the cutoff band of the filter. An impedance matching circuit using a Chebyshev filter consisting of L and C is illustrated in FIGS. 27 to 29 as an impedance matching circuit provided with a variable frequency AC power source Vs.

FIG. 27 relates to the sixth embodiment and is a circuit diagram of an impedance matching circuit using an LPF as an output impedance. FIG. 28 relates to the seventh embodiment and is a circuit diagram of an impedance matching circuit using an HPF as an output impedance. FIG. 29 relates to the eighth embodiment and is a circuit diagram of an impedance matching circuit using a BPF as an output impedance.

Zi in the impedance matching circuit of FIG. 27 is impedance which saw FIG. 27 with the broken line (2) and looked at the variable frequency alternating current power source Vs side (left side in FIG. 27). First, the impedance Z _{K + 1} when the variable frequency AC power source Vs side (left side in FIG. 27) is cut by broken line (K + 1) in FIG.

It becomes. However, K + 1 <final stage N.

In an ordinary filter, each is counted as one stage, but in this case, two circuit elements of L and C are one set. In order to set the impedance of each of the input and output to 50 Ω, the number of stages is odd. The impedance Z _N of the final stage N is

It becomes.

Similarly, Zi in the impedance matching circuit of FIG. 28 is shown. The impedance Z _{K + 1} when the variable frequency AC power source Vs side (left side in FIG. 28) is cut by broken line (K + 1) in FIG.

It becomes. However, K + 1 <final stage N. Also in FIG. 28, two circuit elements of L and C are one set. In order to set the impedance of each of the input and output to 50 Ω, the number of stages is odd. The impedance Z _N (= Zi) of the final stage N is

It becomes.

Similarly, Zi in the impedance matching circuit of FIG. 29 is shown. The impedance Z _{K + 1} when the variable frequency AC power source Vs side (left side in FIG. 29) is cut by broken line (K + 1) in FIG.

It becomes. In BPF, N-1 indicates the number of filter stages, and N indicates the number of C. The impedance Z _N (= Zi) of the output is

It becomes.

Next, the value of the circuit element is determined. In the LPF, the values of L and C are determined on the basis of the ripple of the Chebyshev filter, the number of filter stages, and the procedure in which the imaginary part of Zi becomes 0Ω at the lower limit of the desired frequency band. The target maximum reflection coefficient is determined by the ripple and the number of filter stages. An example of 9 stages is shown in FIGS. 30 to 32 for the LPF (ripple 0.5).

In the Chebyshev LPF, when the ripple is 0.5 and nine stages, the target maximum reflection coefficient is 0.8. As before, Zi has a locus going outward from the origin on the Smith chart (see FIG. 30).

Next, when the impedance Zii (output impedance) is cut on the Smith chart when cut along the broken line (1) in FIG. 27 and looking at the variable frequency AC power source Vs side (left side in FIG. 27), As shown in FIG. 31, it has a spiral trajectory.

Similar to the first embodiment and FIG. 8, the impedance of 10 points is randomly given sparsely in the Smith chart circle, and the reflection coefficient γiii when reflection occurs at the broken line (3) in FIG. 27 is shown in FIG. It can be seen from FIG. 32 that at all loads, there are one or more frequencies at which the reflection coefficient γiii is −10 dB or less.

In the case of the HPF, it is symmetrical at the center frequency with the LPF. In the LPF, the lower limit frequency is used as a reference, but in the HPF, the upper limit frequency is a reference. Therefore, the values of L and C are determined based on the ripple of the Chebyshev filter, the number of filter stages, and the procedure in which the imaginary part of Zi becomes 0 Ω at the upper limit of the desired frequency band. As in the case of the LPF, the target maximum reflection coefficient is determined by the ripple and the number of filter stages.

For Chebyshev HPF, for a ripple of 0.5 and 9 stages, the target maximum reflection coefficient is 0.8. As before, Zi has a locus going outward from the origin on the Smith chart (see FIG. 33). However, the origin is the upper limit frequency, and the unit circle direction side of the Smith chart is the lower limit frequency.

Next, when impedance Zii is plotted on a Smith chart when cut along the broken line (1) in FIG. 28 and looking at the variable frequency AC power source Vs side (left side in FIG. 28), it is shown in FIG. It becomes a spiral trajectory.

Similar to Embodiment 1 and FIG. 8, the impedance of 10 points is randomly given sparsely within the Smith chart circle, and the reflection coefficient γiii when reflection occurs at the broken line (3) of FIG. 28 is shown in FIG. It can be seen from FIG. 35 that at all the loads, there are one or more frequencies at which the reflection coefficient γiii is −10 dB or less.

BPF can be considered as a filter that has both LPF and HPF. Even with the same ripple and the number of filter stages, either the procedure in which the imaginary part of Zi becomes 0Ω at the lower limit of the desired frequency band or the procedure in which the imaginary part of Zi at the upper limit of the desired frequency band becomes 0Ω can be taken. The eighth embodiment shows a procedure in which the imaginary part of Zi becomes 0 Ω at the lower limit of the desired frequency band.

FIG. 36 shows Zi when the ripple is 0.1 and the number of filter stages is three. The target maximum reflection coefficient is 0.9. As before, Zi is a trajectory going outward from the origin on the Smith chart.

Next, when impedance Zii is plotted on a Smith chart when cut along the broken line (1) in FIG. 29 and looking at the variable frequency AC power source Vs side (left side in FIG. 29), it is shown in FIG. It becomes a spiral trajectory.

Similar to Embodiment 1 and FIG. 8, impedances of 10 points are randomly given sparsely within the Smith chart circle, and a reflection coefficient γiii when reflection occurs at the broken line (3) of FIG. 29 is shown in FIG. It can be seen from FIG. 38 that at all the loads, there are one or more frequencies at which the reflection coefficient γiii is −10 dB or less.

In the case of the same ripple value in the Chebyshev filter, the spiral trajectory becomes larger as the number of stages is larger. Further, in the case of the same number of filter stages, the larger the ripple value, the larger the size of the spiral trajectory, and the range of complex conjugate matching is broadened.

According to the impedance matching circuit of any of the sixth to eighth embodiments, in addition to the effects of the embodiment shown in FIG. 4 and the first embodiment, at least one lumped constant element (L or C) is provided. As a result, the impedance matching circuit can be miniaturized, and the design of the impedance matching circuit is facilitated.

1, 2, 3 Impedance matching circuit a, b, c, d Transmission line C, C1, C2, C3 Capacitor CL, CL1, CL2 Coupled line L Inductor V Fixed frequency AC power source Vs Variable frequency AC power source ZL Desired target Load indicated by impedance

Claims (7)

1. A variable frequency AC power source is provided and connected to a desired target load,
   The frequency of the variable frequency AC power source is changed, and the locus of the output impedance is spirally displayed on the Smith chart, and the output impedance is matched or within a desired numerical range with respect to the impedance which becomes the complex conjugate of the impedance of the target load. Impedance matching circuit to fit into.
2. The impedance matching circuit according to claim 1, wherein there are a plurality of frequency ranges in which the output impedance matches or falls within a desired numerical range with respect to an impedance that is a complex conjugate of the impedance of the target load.
3. The impedance matching circuit according to claim 1 or 2, wherein an impedance that is a complex conjugate of the impedance of the target load is plotted at a predetermined position on the entire surface of the Smith chart.
4. The impedance matching circuit according to any one of claims 1 to 3, wherein a frequency range in which the frequency of the variable frequency alternating current power source is changed is a desired frequency range.
5. The impedance matching circuit according to any one of claims 1 to 4, comprising at least one transmission line.
6. The impedance matching circuit according to any one of claims 1 to 5, comprising at least one coupled line.
7. The impedance matching circuit according to any one of claims 1 to 6, comprising at least one lumped constant element.

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