JP2014011475A - Matching circuit and antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a matching circuit which does not require a plurality of control devices, by limiting the voltage supply source of a PIN diode, as a switching element, to only one without using a variable element of large loss such as a varicap diode.SOLUTION: A matching circuit 20 including a first passive element 40a connected with an antenna 1, and a second passive element 40b connected in parallel with the first passive element 40a is further provided with a voltage supply terminal 6 for applying a control voltage to the first passive element 40a and second passive element 40b, a first voltage division circuit 30a having one end connected with the voltage supply terminal 6 and the other end connected with one end of the first passive element 40a, and a second voltage division circuit 30b having one end connected with the voltage supply terminal 6 and the other end connected with one end of the second passive element 40b. The first passive element 40a and second passive element 40b are controlled externally and simultaneously by a single voltage supply source.

Description

  The present invention relates to a matching circuit and an antenna device for adjusting the frequency of an antenna in a wireless device such as a portable terminal.

In recent years, in wireless devices such as mobile phones, the number of antennas tends to increase as the number of wireless systems increases. Further, the occupied volume allowed for the antenna tends to be reduced, and there is a strong demand for miniaturization of the internal antenna. However, the antenna characteristics are generally in a trade-off relationship with the size, and with the progress of miniaturization, narrowing of the frequency band and deterioration of efficiency become problems.
As a solution to this problem, a technique has been proposed in which a single antenna element is used, and the tuning frequency is made variable by changing the capacitance value of the varicap diode (see Patent Document 1).
As a technique for changing the element value of the matching circuit, a technique using a PIN diode as a switching element has been proposed (see Patent Document 2).
In this variable technique, matching elements are connected to a plurality of switching elements, and the switching elements are selectively turned on / off to realize a desired frequency.

JP 2002-232313 A JP 2011-35505 A

  Patent Document 1 discloses an antenna device in which a varicap diode is connected as a variable capacitance element to a feeding portion of a monopole antenna. In this antenna, by changing the voltage applied to the varicap diode, it is possible to change the capacitance value which is a matching element to correspond to a desired frequency. However, in this method, the problem that the influence of the loss of the varicap diode directly deteriorates the characteristics of the antenna cannot be avoided. In particular, in an application with a frequency of 1 GHz or more where the loss of the varicap diode is large, the antenna characteristics are significantly deteriorated, which becomes a problem.

Patent Document 2 discloses an antenna device in which two inductors connected in series to an antenna feeding unit and a PIN diode as a switching element are connected in parallel to each inductor. This antenna is provided with a device capable of independently controlling the switches of the respective PIN diodes, and the values of four matching elements can be realized from combinations of ON and OFF states. Arbitrary four frequencies can be selected from the matching element values. However, in this method, the number of voltage supply sources for controlling the respective PIN diodes is the same as that of the switching elements, so that the circuit structure is complicated. Further, since a control device is required, an increase in cost and circuit is inevitable. Further, when the voltage supply source is put into service, there is a problem that the switching selectivity is lost.

The present invention has been made in view of the above, and an object thereof is to provide a matching circuit that is configured with a simple circuit and can be controlled by a single voltage supply source.

  To achieve the above object, a matching circuit according to the present invention includes a first switching element connected in series, a first passive element unit having a first passive element, a second switching element connected in series, and a second switching element. A second passive element unit having two passive elements and connected in parallel to the first passive element unit; and for applying a control voltage to the first passive element unit and the second passive element unit A voltage supply terminal, one end connected to the voltage supply terminal, the other end connected to one end of the first passive element section, and one end connected to the voltage supply terminal. Thus, the first feature is that a second voltage dividing circuit having the other end connected to one end of the second passive element portion is provided.

According to the present invention having the above characteristics, the first switching element is turned on first by continuously applying a voltage from the voltage supply terminal. Thereafter, when a voltage is applied, the first and second switching elements are simultaneously turned ON. Therefore, when the present invention is combined with an antenna device, the connection of the passive element portion can be configured in two ways as the state of the matching circuit, and the antenna frequency can be varied over a wide range.

In addition, since a supply voltage source and a control device corresponding to each switching element are not necessary, the circuit can be simplified. As a result, the transmission line can be shortened and deterioration of the antenna characteristics can be prevented.

Furthermore, the matching circuit according to the present invention is characterized in that the first and second passive elements are capacitors or inductors.

According to the matching circuit of the above characteristics, when the passive element is a capacitor, the impedance can be changed to capacitive, and when the passive element is an inductor, the impedance can be changed to inductive, so that the impedance can be easily adjusted. It becomes.

Furthermore, the matching circuit according to the present invention has a third feature that the first and second switching elements are PIN diodes.

According to the matching circuit having the above characteristics, the switching element can be reduced in size by using the PIN diode, and therefore the size of the entire matching circuit can be reduced.

Furthermore, the matching circuit according to the present invention is a first voltage dividing circuit, the first resistor having one end connected to the voltage supply terminal, the one end connected to the other end of the first resistor, and the other end Consists of a second resistor connected to a reference potential. As a second voltage dividing circuit, one end is connected to the voltage supply terminal, and one end is connected to the other end of the third resistor. The fourth feature is that the other end is composed of a fourth resistor connected to the reference potential.

According to the matching circuit having the above characteristics, it is possible to reduce the size of the matching circuit by using a resistance element as a component of the voltage dividing circuit, and therefore, the size of the entire matching circuit can be reduced.

Furthermore, the matching circuit according to the present invention has a fifth feature that the second passive element portion is connected to the first passive element portion via a third capacitor.

  According to the matching circuit having the above characteristics, it is possible to prevent the supply voltage from being applied to the second switching element via the first voltage dividing circuit by disposing the third capacitor. This makes it possible to accurately control the switching element.

Furthermore, the matching circuit according to the present invention is characterized in that a first inductor is provided between the voltage supply terminal and the second voltage dividing circuit.

  According to the matching circuit having the above characteristics, by providing the third inductor, it is possible to prevent a high frequency component due to coupling with the high frequency line connected to the antenna from flowing into the voltage supply source, and to stabilize the power supply source. Can be achieved.

Furthermore, the first resistor of the matching circuit according to the present invention has a lower resistance value than the second resistor, the third resistor has a higher resistance value than the fourth resistor, and the voltage dividing ratio is the second resistance value. The seventh feature is that the first voltage dividing circuit is larger than the voltage dividing circuit.

  According to the matching circuit having the above characteristics, by changing the ratio between the first and second resistors connected to the first switching element and the third and fourth resistors connected to the second switching element. The voltage dividing ratio of the voltage applied to each switching element can be changed. As a result, a plurality of switching elements can be controlled by a single voltage supply source.

Furthermore, the matching circuit according to the present invention includes a first high frequency cut element having one end connected to the other end of the first voltage dividing circuit and the other end connected to one end of the first switching element, One end is connected to the other end of the first switching element, and the other end is connected to a reference potential, and the other end is connected to the other end of the second voltage dividing circuit. A third high-frequency cut element having the other end connected to one end of the second switching element, one end connected to the other end of the second switching element, and the other end connected to a reference potential. An eighth characteristic is that the fourth high-frequency cut element is provided.

  According to the matching circuit having the above characteristics, the high-frequency signal and the DC signal that is the supply voltage can be separated by connecting the high-frequency cut element. As a result, attenuation of the high-frequency signal can be prevented and the switching element can be accurately controlled.

Furthermore, the matching circuit according to the present invention has a ninth feature that the first, second, third and fourth high frequency cut elements are choke coils.

According to the matching circuit having the above characteristics, the use of the choke coil as the high-frequency cut element can efficiently prevent the passage of the high-frequency signal. Moreover, since it can respond with a chip inductor, mounting is easy.

Furthermore, an antenna device according to the present invention has a tenth feature including an antenna and a matching circuit described in any one of the first to ninth features connected to the antenna.

  According to the antenna device having the above characteristics, an arbitrary matching element can be selected by controlling the supply voltage from the voltage supply terminal. Therefore, an antenna device corresponding to a plurality of frequencies can be realized with one antenna element, and the device can be downsized and the number of parts can be reduced.

According to the present invention, a plurality of voltage supply sources and control devices for controlling the switching elements are unnecessary. Therefore, it is configured with a simple circuit, and it is possible to adjust the frequency of the antenna in a wide band by controlling the states of at least two matching circuits with a single voltage supply source.

1 is a circuit diagram (simplified diagram) of a matching circuit according to an embodiment of the present invention. FIG. 3 is a circuit diagram illustrating a specific circuit configuration of the matching circuit according to the first embodiment. It is explanatory drawing of operation | movement of the matching circuit of FIG. It is the schematic diagram showing VSWR at the time of using the matching circuit which concerns on 1st Embodiment for an antenna apparatus. It is the schematic diagram showing the efficiency at the time of using the matching circuit which concerns on 1st Embodiment for an antenna apparatus. It is an illustration figure of the layout in case the matching circuit of 1st Embodiment is mounted in a mobile telephone as an antenna apparatus. It is a circuit diagram of the antenna apparatus of a comparative example. FIG. 6 is a simplified diagram of a matching circuit according to a second embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. Further, various modifications can be made to the present embodiment without departing from the spirit of the present embodiment.

FIG. 1 is a simplified diagram of a matching circuit 20 for switching the operating frequency of an antenna mounted on a radio. The matching circuit 20 includes a first passive element unit 40a having a first PIN diode 3a that is a first switching element connected to an antenna 1 that transmits and receives radio waves, and a first capacitor 2a that is a first passive element. And a second passive element unit that is connected in parallel to the first passive element unit 40a and has a second PIN diode 3b that is a second switching element and a second capacitor 2b that is a second passive element. 40b, a voltage supply terminal 6 for applying a control voltage to the first passive element part 40a and the second passive element part 40b, one end connected to the voltage supply terminal 6, and the other end to the first The first voltage dividing circuit 30a connected to one end of the passive element section 40a, one end connected to the voltage supply terminal 6, and the other end connected to one end of the second passive element section 40b. Second minute And it includes a circuit 30b.

The first voltage dividing circuit 30a has one end connected to the voltage supply terminal 6 via the second connection node 8 and one end other than the first resistor 4a. The second voltage dividing circuit 30b is connected to one end and the other end is connected to a reference potential. One end of the second voltage dividing circuit 30b is supplied with the voltage via the second connection node 8. A third resistor 4b connected to the terminal 6 and a fourth resistor 5b having one end connected to the other end of the third resistor 4b and the other end connected to a reference potential. . In the matching circuit 20, the second passive element unit 40b is further connected to the first passive element unit 40a via the first connection node 7 and the third capacitor 9 for DC cut.

(First embodiment)
FIG. 2 shows a specific circuit configuration of the matching circuit 20 according to the first embodiment. The antenna 1 is connected to one end of each of the first passive element unit 40 a and the second passive element unit 40 b connected in parallel, and is connected to the transceiver 11 via the fourth capacitor 13. Further, a first inductor 14 for cutting high frequency noise is provided, one end of which is connected to the second connection node 8 and the other end is connected to one end of the third resistor 4b. The resistance value of each resistor is such that the first resistor 4a has a lower resistance value than the second resistor 5a, and the third resistor 4b has a higher resistance value than the fourth resistor 5b. . For this reason, the first voltage dividing circuit 30a has a larger voltage dividing ratio than the second voltage dividing circuit 30b.

Further, the matching circuit 20 is a first high-frequency cut element having one end connected to the other end of the first voltage dividing circuit 30a and the other end connected to one end of the first switching element 3a. 1 choke coil 12a and a second choke coil 12b which is a second high frequency cut element having one end connected to the other end of the first switching element 3a and the other end connected to a reference potential. And a third high-frequency cut element having one end connected to the other end of the second voltage dividing circuit 30b and the other end connected to one end of the second switching element 3b. A choke coil 12c, and a fourth choke coil 12d which is a fourth high frequency cut element having one end connected to the other end of the second switching element 3b and the other end connected to a reference potential. Yes. The first, second, third, and fourth choke coils 12a, 12b, 12c, and 12d play a role of preventing the passage of a high-frequency signal without affecting the DC signal. The same effect can be obtained by using a resistance element instead of the choke coil.

The first and second PIN diodes 3 a and 3 b function as switching elements, and a voltage supply source 15 for controlling ON / OFF thereof is connected via the second connection node 8. The fourth capacitor 13 is for adjusting the impedance of the antenna, and the first inductor 14 is for cutting high frequency noise.
With these structures, it is possible to arbitrarily select a matching element even when a voltage is simultaneously supplied to two PIN diodes from a single voltage supply source. As a result, the circuit can be simplified and the cost and circuit loss can be reduced.

A specific operation of the matching circuit 20 is shown in FIG. By gradually increasing the control voltage, the first and second PIN diodes 3a and 3b are continuously turned on. That is, when the voltage is low, the PIN diode 3a is turned on. When the voltage is continuously increased, the first PIN diode 3a and the second PIN diode 3b are turned on. Further, the capacitance in each state is C1 when the voltage is low and C1 + C2 when the voltage is high.

FIG. 4 is a schematic diagram showing VSWR characteristics when the matching circuit of FIG. 2 is used in an antenna device. In this figure, the vertical axis represents VSWR (voltage standing wave ratio), and the horizontal axis represents frequency.

FIG. 5 is a schematic diagram showing radiation efficiency characteristics when the matching circuit of FIG. 2 is used in an antenna device. In this figure, the vertical axis represents radiation efficiency and the horizontal axis represents frequency.

The indications of states 1 and 2 shown in the graphs of FIGS. 4 and 5 indicate the ON / OFF states of the first and second PIN diodes 3a and 3b as switching elements. As can be seen from these figures, by switching the matching circuit according to the two states of the first and second PIN diodes 3a and 3b, the GPS frequency band (1.575 GHz) to the W-LAN frequency band (2.44 GHz). Variable frequency 2 state is realized. The frequency changes in FIGS. 4 and 5 show an example and are adjusted according to the actual antenna configuration and the wireless device terminal.

For example, the resistance value of this example is the first resistor 4a = 100Ω, the second resistor 5a = 200Ω, the third resistor 4b = 200Ω, the fourth resistor 5b = 100Ω, and the supply voltage is the standard forward voltage. Therefore, the low voltage value is 1.2V and the high voltage value is 2.4V. In this case, the resistance value of each resistor is such that the first resistor 4a has a lower resistance value than the second resistor 5a, and the third resistor 4b has a higher resistance value than the fourth resistor 5b. is there. Therefore, the voltage dividing ratio is higher in the first voltage dividing circuit 30a (ratio 0.67) than in the second voltage dividing circuit 30b (ratio 0.33). As a result, the matching circuit 20, when a low voltage is supplied from the voltage supply source 15, the first PIN diode 3 a is turned on and the second PIN diode 3 b is turned off.

The first and second capacitors 2a and 2b connected in parallel to the antenna 1 are matching elements for frequency adjustment, and the fourth capacitor 13 connected in series is a matching element for impedance adjustment. The capacitance values in this example are, for example, the first capacitor 2a = 0.1 pF, the second capacitor 2b = 1.5 pF, and the fourth capacitor 13 = 0.5 pF. That is, in the W-LAN frequency band (state 1), the parallel connection capacitor selects C1 (0.1 pF), and in the GPS frequency band (state 2), the parallel connection capacitor selects C1 + C2 (1.6 pF). It is possible to select two different applications. Since the capacitance values of these capacitors depend on the distance between the antenna element and the GND, the capacitance values are adjusted to match the characteristics of each antenna when connected to an actual antenna.

FIG. 6 shows an example of a mounting layout when the matching circuit 20 is mounted on a mobile phone as an antenna device. A feeding point 16, a matching circuit 20, and a transceiver 11 are provided on the mounting substrate 17. The mounting substrate 17 is a substrate on which general-purpose electronic components are mounted, and is built in the mobile phone. The antenna element is connected to the feeding point 16. As a material for the mounting substrate 17, ABS resin, FR4, or the like can be used.

In this embodiment, a varicap diode is not used as a variable matching element for changing the frequency, and a matching circuit is realized by selecting a capacitor using a PIN diode as a switching element. According to this configuration, since no varicap diode is used, it is possible to avoid deterioration of antenna characteristics due to loss of the varicap diode. This avoidance of characteristic deterioration is particularly useful at a frequency of 1 GHz or more. Furthermore, since the capacitance value can be changed larger than that of the varicap diode, the frequency can be varied over a wide frequency range.

(Comparative example)
As a comparative example, FIG. 7 shows a circuit diagram of a conventional antenna device. According to this structure, the same number of voltage supply sources (Vb1, Vb2) and control devices as PIN diodes (D4, D5) are required. However, in the present invention, since the voltage supply source 15 of the PIN diode is one regardless of a plurality of PIN diodes, a control device is not required. Therefore, the complexity of the circuit and the increase in circuit loss can be avoided. In addition, the cost can be reduced because the number of parts is reduced.

In the present invention, when all the PIN diodes are ON, the state of the lowest frequency is obtained. At this time, since all the PIN diodes are connected in parallel, the high frequency resistance of the PIN diode is minimized. This can reduce the loss of the entire PIN diode. Further, since the capacitor 13 for impedance adjustment is connected immediately before the transmitter / receiver 11 separately from the matching circuit 20, adjustment according to the individual antenna and the transmitter / receiver is easy.

(Second Embodiment)
FIG. 8 shows a simplified diagram of a matching circuit according to the second embodiment. The difference from the matching circuit according to the first embodiment shown in FIG. 2 is that the passive element section and the voltage dividing circuit are connected in three stages in parallel. Although the matching circuit 20 can be switched in two stages, it can be switched in three stages by connecting the third voltage dividing circuit 30c and the third passive element unit 40c in parallel. At this time, the first switching element is turned on at a low voltage, the first and second switching elements are turned on at a medium voltage, and the first, second, and third switching elements are turned on at a high voltage. In addition, the voltage dividing ratio is the relationship of the first voltage dividing circuit 30a, the second voltage dividing circuit 30b, and the third voltage dividing circuit 30c in the order of high ratio.

The present invention is effective for an application of 1 GHz or more (for example, a composite antenna that switches multi-frequency antenna frequencies such as GPS, W-LAN, Bluetooth (registered trademark)) mounted on a portable wireless device.

The present invention can also be configured in one chip with a thin film structure. By configuring in one chip, the height and size can be reduced, and the line loss can be reduced.

Although the preferred embodiments of the present invention have been described above, modifications other than those described above can be made.

  As described above, the matching circuit according to the present invention is a low-loss matching circuit capable of adjusting the antenna frequency over a wide band. With this matching circuit, an antenna that can be used for a plurality of applications using a single antenna element can be realized. Therefore, the antenna can be reduced in size, the number of parts can be reduced, and the added value of the antenna can be greatly improved.

DESCRIPTION OF SYMBOLS 1 Transmission / reception antenna 2a 1st capacitor | condenser, 2b 2nd capacitor | condenser, 2c 5th capacitor | condenser 3a 1st PIN diode, 3b 2nd PIN diode 3c 3rd PIN diode 4a 1st resistance, 4b 3rd 3rd Resistor 4c fifth resistor 5a second resistor 5b fourth resistor 5c sixth resistor 6 voltage supply terminal 7 first connection node 8 second connection node 9 third capacitors 10a, 10b, 10c 10d, 10e, 10f, 10g, 10h, 10i Reference potential (GND)
11 Transceiver 12a First choke coil, 12b Second choke coil 12c Third choke coil, 12d Fourth choke coil 13 Fourth capacitor 14 First inductor 15 Voltage supply source 16 Feed point 17 Mounting substrate 18 Sixth capacitor 20 Matching circuit 30a First voltage divider circuit, 30b Second voltage divider circuit, 30c Third voltage divider circuit 40a First passive element portion, 40b Second passive element portion 40c Third passive Element part

Claims (10)

A first passive element unit having a first switching element and a first passive element connected in series;
A second passive element unit having a second switching element and a second passive element connected in series, and connected in parallel to the first passive element unit;
A voltage supply terminal for applying a control voltage to the first passive element section and the second passive element section;
A first voltage dividing circuit having one end connected to the voltage supply terminal and the other end connected to one end of the first passive element unit;
A matching circuit comprising: a second voltage dividing circuit having one end connected to the voltage supply terminal and the other end connected to one end of the second passive element unit. The matching circuit according to claim 1, wherein the first and second passive elements are capacitors or inductors. The matching circuit according to claim 1, wherein the first and second switching elements are PIN diodes. A first resistor having one end connected to the voltage supply terminal as the first voltage dividing circuit;
One end is connected to the other end of the first resistor, and the other end is composed of a second resistor connected to a reference potential.
As the second voltage dividing circuit, a third resistor having one end connected to the voltage supply terminal;
The matching circuit according to claim 1, wherein the matching circuit includes a fourth resistor having one end connected to the other end of the third resistor and the other end connected to a reference potential. The matching circuit according to claim 1, wherein the second passive element unit is connected to the first passive element unit via a third capacitor. The matching circuit according to claim 1, further comprising a first inductor between the voltage supply terminal and the second voltage dividing circuit. The first resistor has a lower resistance value than the second resistor, the third resistor has a higher resistance value than the fourth resistor, and a voltage dividing ratio is higher than that of the second voltage dividing circuit. 5. The matching circuit according to claim 4, wherein the first voltage dividing circuit is larger. A first high-frequency cut element having one end connected to the other end of the first voltage dividing circuit and the other end connected to one end of the first switching element; and one end of the first switching element The second high-frequency cut element is connected to the other end, the other end is connected to a reference potential, one end is connected to the other end of the second voltage dividing circuit, and the other end is the second A third high frequency cut element connected to one end of the switching element, and a fourth high frequency cut element connected at one end to the other end of the second switching element and connected at the other end to a reference potential. The matching circuit according to claim 1, further comprising: 9. The matching circuit according to claim 8, wherein the first, second, third and fourth high frequency cut elements are choke coils. The antenna apparatus which has an antenna and the matching circuit in any one of Claims 1-9 connected to the said antenna.

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