JP2012023487A - Antenna matching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna matching device capable of automatically adjusting impedance matching in a main antenna.SOLUTION: A receiver 1 includes a sub-antenna 11 capable of transmitting a radio wave S2 with the multiplication frequency of a reception frequency fr to a main antenna 2. Generally, an antenna (the main antenna 2) has a characteristic to resonate even by a radio wave with the integral multiple of a reception radio wave S1 in the same way as the reception radio wave S1. Consequently, in this embodiment, when the main antenna 2 receives the multiplication frequency radio wave S2, the constant number of a matching circuit 4 is adjusted by the multiplication frequency radio wave S2, so as to obtain impedance matching between the main antenna 2 and a reception circuit 3 concerning the reception radio wave S1.

Description

  The present invention relates to an antenna matching device that performs impedance matching of an antenna.

  Conventionally, it has been known that a communication device such as a receiver or a transmitter cannot efficiently transmit a signal if the impedance is different between the antenna side of the communication device and the circuit side in the communication device. Therefore, in general, a communication device is equipped with a matching circuit that matches the impedance of the antenna (see Patent Document 1 and the like). By adjusting the matching circuit, the impedance of the antenna viewed from the matching circuit is set to a predetermined value. By matching the antenna impedance, the impedance of the antenna is matched.

JP 2001-77719 A

  By the way, when a communication device is installed at the installation location, if there is a metal or the like around the installation location, the antenna is affected by this metal, causing a mismatch in impedance matching between the antenna and the communication circuit. There is a possibility. In this case, since the impedance matching adjusted by the matching circuit is deviated, there is a problem in that efficient signal transmission is affected. Generally, since the matching circuit is a fixed value designed, it cannot be switched freely, and there is a need to adjust the matching according to the use environment.

  An object of the present invention is to provide an antenna matching device capable of automatically adjusting impedance matching of a main antenna.

  In order to solve the above problems, in the present invention, a communication main antenna having an impedance matching function for matching impedances of an antenna and a radio circuit, and a frequency multiplied by a frequency of a main radio wave handled by the main antenna for communication. An adjustment circuit that automatically adjusts impedance matching of the main antenna based on the power level of the radio wave transmitted from the sub-antenna among radio waves received by the main antenna. The summary is provided.

  According to this configuration, the sub-antenna transmits the radio wave multiplied by the main radio wave from the main antenna, and the main antenna receives the radio wave having the multiplied frequency transmitted from the sub-antenna. Based on the power level of the radio wave, Impedance matching is automatically adjusted. By the way, since the antenna has a characteristic of resonating at a multiplied frequency, if the radio wave has a multiplied frequency, the gain of the antenna also has a characteristic that changes so that a peak occurs at the multiplied frequency. Therefore, if the impedance matching of the main antenna is adjusted with the multiplied frequency radio wave as in this example, the impedance of the main radio wave is also matched as a result, so it is possible to indirectly match the impedance of the main radio wave It becomes.

In the present invention, the adjustment circuit distributes and extracts a radio wave immediately after passing through the impedance matching function of the main antenna, a filter that filters only the multiplied frequency that has passed through the distributor, The gist is provided with a detector for detecting the multiplied frequency via a filter, and a processing circuit for adjusting the impedance matching function based on the power level of the radio wave detected by the detector.
According to this configuration, the impedance matching of the main antenna can be automatically adjusted by a general-purpose circuit group such as a distributor, a filter, and a detector.

  The gist of the present invention is that the frequency of the radio wave transmitted from the sub-antenna is a multiplication of the oscillation frequency used inside the radio circuit.

According to this configuration, since the radio wave transmitted from the sub-antenna is generated using the oscillation frequency of the wireless circuit, it is not necessary to prepare a new oscillator for generating this radio wave.
In the present invention, in the case of the super tehrodyne system, the frequency of the radio wave transmitted from the sub-antenna is a local part of a PLL system local oscillator (for example, a VCO: voltage controlled oscillator) necessary for generating an intermediate frequency in the radio circuit. The gist is that the oscillation frequency is multiplied or a reference frequency (for example, a frequency of a crystal oscillator) for generating the oscillation frequency of the local oscillator is multiplied.

  According to this configuration, since the frequency of the radio wave transmitted from the sub-antenna is set based on the local oscillation frequency or the reference oscillation frequency output from the local oscillator, the local oscillator that originally exists in the radio is used. It becomes possible to set the frequency of the radio wave of the sub antenna.

  The gist of the present invention is that there is provided adjustment correction means for adjusting the impedance matching while allowing a difference when a radio wave generated from the oscillation frequency does not multiply the main radio wave.

  According to this configuration, even if the radio wave generated from the oscillation frequency is not multiplied by the main radio wave, the impedance matching can be adjusted by the adjustment correction unit, so that automatic adjustment can be performed more accurately.

The gist of the present invention is that the adjustment circuit is not activated at the frequency of the radio wave transmitted from another device, but is activated only at the radio wave transmitted from the sub-antenna.
According to this configuration, even when the main antenna receives a jamming radio wave from another device, the impedance matching operation is not performed on the radio wave, so that the accuracy of the matching operation can be ensured.

  The gist of the present invention is that the main antenna is an inverted L-shaped antenna having an antenna wire having an approximately L-shape, and the sub-antenna is a pattern antenna formed on a substrate of the approximately L-shaped antenna. .

  According to this configuration, since the inverted L-shaped antenna has an advantage of being small, if the inverted L-shaped antenna is used as the main antenna as in the present configuration, the size of the entire antenna can be suppressed small.

  According to the present invention, impedance matching of the main antenna can be automatically adjusted.

The block diagram of the receiver of 1st Embodiment. The wave form diagram which shows the detection signal of a multiplication frequency electromagnetic wave. The perspective view which shows the antenna structure of a receiver. (A) is a circuit diagram of a matching circuit, (b) is a graph which shows the relationship between the voltage applied to the varactor diode of a matching circuit, and its electric charge. The correlation figure of the frequency and gain which show the principle of the antenna matching automatic adjustment of this example. The Smith chart which shows the impedance locus | trajectory of the main antenna of 2nd Embodiment. The graph which shows the variable range of a variable capacitance diode. The block diagram of the matching circuit of another example.

(First embodiment)
Hereinafter, a first embodiment of an antenna matching apparatus embodying the present invention will be described with reference to FIGS.

  As shown in FIG. 1, a single super tehrodyne receiver 1 (hereinafter simply referred to as a receiver 1) includes a communication main antenna 2 and a receiving circuit that demodulates received radio waves S1 received by the main antenna 2. 3 is provided. The receiver 1 receives the radio wave by converting the received radio wave S1 into a signal having an intermediate frequency IF by the receiving circuit 3, and amplifying and demodulating this signal. Since the receiver 1 of this example is a single type, the process of converting the received radio wave S1 into the intermediate frequency IF is executed only in one stage.

  A matching circuit 4 that can match the impedance Z1 of the main antenna 2 is connected to the main antenna 2. The impedance Z1 is the impedance on the main antenna 2 side as viewed from the matching circuit 4. The matching circuit 4 adjusts the impedance Z1 and the impedance Z2 on the receiving circuit 3 side viewed from the matching circuit 4 to be substantially the same so that no mismatch occurs in the impedance Z1. The matching circuit 4 is connected to the receiving circuit 3 via a directional coupler 15 of the antenna matching automatic adjustment device 10 to be described later and a filter 5 that can pass only the frequency of the received radio wave S1 (hereinafter referred to as reception frequency fr). It is connected. The receiving circuit 3 and the filter 5 constitute a wireless circuit.

  The receiving circuit 3 is provided with a local oscillator 6 that generates a local oscillation frequency flo that serves as a reference for frequency conversion to the intermediate frequency IF. The local oscillator 6 outputs the reference frequency fbs output from the reference oscillator 6a as a local oscillation frequency flo by a PLL (Phase Locked Loop) method. The local oscillator 6 includes a phase comparator 6b, a loop filter 6c, a VCO 6d, and a frequency divider 6e, and controls the phase difference between the reference frequency fbs and the self oscillation frequency while taking feedback of the self oscillation frequency of the VCO 6d. A frequency that matches the reference frequency fbs is generated and output.

  The receiving circuit 3 is provided with an amplifier 7 that amplifies the received radio wave S1 of the main antenna 2 and a mixer 8 that converts the frequency of the amplified received radio wave S1 by the Teherodyne method. The local oscillation frequency flo is multiplied to a multiplication order l by a multiplier 9 and output to the mixer 8 as a local oscillation frequency l × flo of l times. The mixer 8 generates an intermediate frequency IF by subtracting l times the local oscillation frequency l × flo from the reception frequency fr of the reception radio wave S1.

  The receiver 1 of this example is provided with an antenna matching automatic adjustment device 10 that automatically adjusts the matching circuit 4 by the receiver 1 itself. By the way, when the receiver 1 is installed, for example, near a metal part, the impedance Z1 of the main antenna 2 changes compared to the impedance Z1 of the main antenna 2 before the influence of the metal due to the influence of the metal part. As a result, the matching between the matching circuit 4 and the impedance Z1 may be shifted. Therefore, in this example, the antenna matching automatic adjustment device 10 is provided in the receiver 1 to automatically eliminate the alignment shift caused by the presence of metal parts nearby.

  In this case, the receiver 1 is provided with a sub-antenna 11 capable of transmitting a radio wave obtained by multiplying the reception frequency fr by an integer m (hereinafter referred to as a multiplied frequency radio wave S2). The sub antenna 11 is connected to the local oscillator 6 via the amplifier 12, the multiplier 13, and the switch 14. When the switch 14 is on, the local oscillation frequency flo is output to the multiplier 13 whose multiplication order is n, and the frequency is multiplied by n by the multiplier 13. Therefore, the local oscillation frequency flo is output to the sub-antenna 11 through the amplifier 12 as an n-fold local oscillation frequency n × flo.

  The frequency of the multiplied frequency radio wave S2 in this example (hereinafter referred to as the multiplied frequency m × fr) is set to a value that satisfies “m × fr = n × flo”. For example, when the local oscillation frequency fl is 21.5 MHz and the reception frequency fr is 430 MHz, if n is 40, it is possible to obtain twice the reception frequency fr, that is, a multiplied frequency m × fr of 860 MHz.

  A directional coupler 15 is connected between the matching circuit 4 and the filter 5 to branch the signal received by the main antenna 2 at a constant rate. The directional coupler 15 is connected in series with a filter 16 that can pass only the multiplied frequency m × f and a detector 17 that detects, for example, an envelope of the signal that has passed through the filter 16. The directional coupler 15, the filter 16, and the detector 17 constitute an adjustment circuit.

  As shown in FIG. 2, a high frequency signal of m × fr filtered by the filter 16 is input to the detector 17. The detector 17 performs envelope detection on the multiplied frequency radio wave S2 having the multiplied frequency m × fr, thereby converting it into a detection signal S3 having a predetermined power level (hereinafter referred to as a voltage level) and outputting it.

  As shown in FIG. 1, the receiver 1 is provided with a control circuit 18 that performs overall control of the antenna matching automatic adjustment device 10. The control circuit 18 is connected to the matching circuit 4, the switch 14, and the detector 17. The control circuit 18 turns on the switch 14 at a specific fixed time, for example, periodically or at an engine start operation, and transmits the multiplied frequency radio wave S2 from the sub antenna 11 to the main antenna 2, thereby causing the matching circuit 4 to Perform the adjustment operation.

  Further, the control circuit 18 adjusts the constant of the matching circuit 4 by the voltage level of the detection signal S3 input from the detector 17, that is, the multiplication frequency m × fr, so that the main antenna is related to the reception frequency fr that is originally received radio waves. Impedance matching is performed between the 2 side and the receiving circuit 3 side. Since the control circuit 18 of this example operates by a signal that passes through the filter 16 and the detector 17 that pass only the signal according to the sub-antenna 11, it is activated only by the radio wave transmitted from the sub-antenna 11. That is, the control circuit 18 does not perform the adjustment operation on the frequency component of the radio wave received from another device.

  As shown in FIG. 3, the main antenna 2 is formed of an inverted L-shaped antenna in which an antenna wire is bent into an inverted alphabetical L-shape. The main antenna 2 has a feeding point 19 at the base of the antenna line, and receives power from this point to receive radio waves. The sub-antenna 11 is a pattern antenna formed on the substrate 20 of the inverted L-shaped antenna. The sub antenna 11 has a feeding point 21 at the center of the antenna line.

  An example of the matching circuit 4 is shown in FIG. The matching circuit 4 is provided with an inductance L and a capacitance C0. Capacitance C0 is T-connected to inductance L. In addition, a variable capacitance diode 22 whose capacitance value changes according to the applied voltage is connected in series to the capacitance C0. As the variable capacitance diode 22, for example, a varicap diode or a varactor diode is used. A voltage Vc whose value is controlled by the control circuit 18 is applied to the midpoint 4a between the capacitance C0 and the variable capacitance diode 22. The voltage Vc is biased by a resistor R between the voltage terminal and the midpoint 4a. As shown in FIG. 4B, the capacitance C1 of the variable capacitance diode 22 and the voltage Vc change in a substantially proportional relationship.

  FIG. 5 is a graph showing an image of the gain of the entire antenna unit including the matching circuit 4 viewed from the receiving circuit 3 side when the antenna gain of the main antenna 2 is constant. As shown in FIG. 5, the antenna (main antenna 2) generally has a characteristic of resonating similarly to the received radio wave S1 even with a radio wave having an integral multiple of the received radio wave S1. That is, when the antenna impedance at the same frequency is adjusted by changing the constant of the matching circuit 4 at a predetermined integer multiple frequency (for example, 860 MHz) in the matching circuit 4, the antenna impedance at another integral multiple frequency (for example, 430 MHz) is also obtained. It changes as well. In this example, by using this characteristic, the multiplied frequency radio wave S2 transmitted from the sub-antenna 11 is received by the main antenna 2, and the constant of the matching circuit 4 is adjusted by the multiplied frequency radio wave S2 to indirectly connect the main antenna. The main antenna 2 side and the receiving circuit 3 side are matched with respect to the reception frequency fr of 2.

  In this case, as shown in FIG. 1, the control circuit 18 is provided with a matching circuit automatic adjustment unit 23 that automatically adjusts the matching circuit 4 according to the principle described above. The matching circuit automatic adjustment unit 23 automatically adjusts the matching value of the matching circuit 4 by switching the voltage Vc applied to the variable capacitance diode 22 based on the voltage level of the detection signal S3 when the switch 14 is turned on. Thus, the main antenna 2 side and the receiving circuit 3 side are matched at the reception frequency fr of the main antenna 2. The matching circuit automatic adjustment unit 23 constitutes an adjustment circuit and a processing circuit.

Next, the operation of the antenna matching automatic adjustment device 10 of this example will be described with reference to FIG.
The matching circuit automatic adjustment unit 23 normally stands by with the switch 14 turned off. Then, the matching circuit automatic adjustment unit 23 turns on the switch 14 when the periodic adjustment circuit 4 starts adjusting operation or when the engine is started. At this time, the local oscillation frequency flo is multiplied by n by the multiplier 9, and the multiplied frequency radio wave S2 having a frequency of n × flo is transmitted from the sub antenna 11. The multiplied frequency radio wave S2 is transmitted as a weak radio wave.

  At this time, the main antenna 2 receives both the received radio wave S1 originally handled and the multiplied frequency radio wave S2 from the sub-antenna 11. The filter 5 passes only the reception frequency fr of the reception radio wave S1 and outputs it to the reception circuit 3. The reception circuit 3 converts the reception frequency fr to the intermediate frequency IF and amplifies the signal.

  On the other hand, the filter 16 passes only the multiplied frequency m × fr of the multiplied frequency radio wave S2 and outputs it to the detector 17. The detector 17 envelope-detects the multiplied frequency m × fr that has passed through the filter 16, converts it to a detection signal S 3 having a predetermined voltage level (voltage value), and outputs the detection signal S 3 to the matching circuit automatic adjustment unit 23. To do.

  When the detection signal S3 is input from the detector 17, the matching circuit automatic adjustment unit 23 switches the voltage Vc applied to the variable capacitance diode 22 of the matching circuit 4 based on the voltage level of the detection signal S3. Adjust the constant. As shown in FIG. 5, for example, when the voltage level of the detection signal S3 takes a value lower than the target value Vk, the matching circuit automatic adjustment unit 23 sets the voltage Vc until the voltage level of the detection signal S3 takes the target value Vk. The capacitance C1 of the variable capacitance diode 22 is increased.

  Incidentally, at this time, the constant of the matching circuit 4 is changed according to the voltage level of the signal in accordance with the multiplication frequency m × fr. However, as described above, the matching circuit 4 has a frequency that is an integral multiple of the multiplication frequency m × fr. When the constant is changed, the antenna impedance of the reception frequency fr also changes in the same manner. As a result, the impedance matching of the reception frequency fr is adjusted. Therefore, impedance matching between the main antenna 2 side and the receiving circuit 3 side at the reception frequency fr can be obtained indirectly by taking impedance matching between the main antenna 2 side and the receiving circuit 3 side at the multiplication frequency m × fr. I understand.

  As described above, in the present example, the sub-antenna 11 arranged in the vicinity of the main antenna 2 transmits the multiplied frequency radio wave S2 (frequency m × fr) multiplied by the reception frequency fr of the main antenna 2, and this is transmitted to the main antenna 2 To receive. Then, by adjusting the constant of the matching circuit 4 with the voltage level of the frequency m × fr of the multiplied frequency radio wave S2, impedance matching between the main antenna 2 side and the receiving circuit 3 side is obtained at the reception frequency fr of the main antenna 2. Is possible.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) The sub-antenna 11 for transmitting the radio wave multiplied by the reception radio wave S1 to the main antenna 2 is provided in the receiver 1, and the multi-frequency radio wave S2 transmitted from the sub-antenna 11 is received by the main antenna 2, and the multi-frequency radio wave S2 is received. By adjusting the matching circuit 4 based on the power level, the impedance of the received radio wave S1 is indirectly adjusted. Therefore, impedance matching of the main antenna 2 can be automatically adjusted.

  (2) Since the antenna matching automatic adjustment device 10 is composed of general-purpose circuit groups such as the directional coupler 15, the filter 16, and the detector 17, the main antenna 2 can be used without using a complicated circuit. Impedance matching can be automatically adjusted.

  (3) Since the multiplication frequency m × fr is generated from the local oscillation frequency flo, the multiplication frequency m × fr can be generated using the local oscillator 6 that is originally provided in the receiver 1. Therefore, when generating the multiplied frequency m × fr, it is not necessary to prepare a new oscillator.

  (4) Since the adjustment operation is executed only with the radio wave transmitted from the sub-antenna 11, even if the interference wave is received from another device, the adjustment operation is not executed with this radio wave. Therefore, the accuracy of the adjustment operation can be ensured.

(5) Since the main antenna 2 is an inverted L antenna, the size of the main antenna 2 can be reduced.
(6) Since the sub-antenna 11 is a pattern antenna on the substrate 20 of the main antenna 2, the sub-antenna 11 can be disposed in the vicinity of the main antenna 2. Therefore, the multiplied frequency radio wave S <b> 2 transmitted from the sub antenna 11 can be more reliably received by the main antenna 2. Further, the sub antenna 11 only needs to be able to transmit a weak radio wave, so that a smaller antenna than the main antenna 2 is sufficient.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. The second embodiment is an example in the case where a radio wave multiplied by the frequency of the local oscillator 6 cannot be obtained, and the basic configuration is the same as that of the first embodiment. Therefore, the same parts as those of the first embodiment are denoted by the same reference numerals, detailed description thereof is omitted, and only different parts are described in detail.

  FIG. 6 shows a Smith chart of the impedance Z2 on the main antenna 2 side as viewed from the matching circuit 4. The Smith chart of this example is a chart normalized by 50Ω. Here, since the radio wave multiplied by the reception frequency fr, that is, the radio wave of m × fr is the radio wave of the originally received frequency, if the impedance of the main antenna 2 is matched, the impedance Z2 of this frequency (FIG. 6). Is plotted on the center of the resistance axis 32 of the Smith chart. The resistance axis 32 is a reference axis of an equal reactance circle.

  However, depending on the local oscillator 6 used in the receiving circuit 3, even if the local oscillation frequency fl is multiplied by the multiplier 13, the received frequency fr may not be exactly multiplied. For example, when the multiplication frequency is 860 MHz as in this example, if the local oscillation frequency flo is 22.5 MHz, for example, only 855 MHz (= 22.5 × 38) can be taken as an approximate value. The plot point Pb of the impedance Z2 at this time is located at a location shifted from the center of the resistance axis 32 of the Smith chart.

  Therefore, in this example, when the constant of the matching circuit 4 is adjusted from the voltage level of the detector 17, the constant of the matching circuit 4 is set in consideration of the frequency shift. That is, the constant of the matching circuit 4 is adjusted so that the voltage level of the detector 17 takes a value lower than the target value Vk by a predetermined amount. This function is the correction matching unit 33 shown in FIG. The correction matching unit 33 corresponds to an adjustment correction unit.

  By the way, one index of impedance matching is, for example, a voltage standing wave ratio (VSWR). The voltage standing wave ratio is the ratio of the traveling wave and the reflected wave on the signal transmission path, and the value approaches “1” if the reflected wave is small. In the case of the second embodiment, since the impedance Z2 deviates from the center of the Smith chart, the voltage standing wave ratio takes a value deviating from “1”.

  One index of impedance matching is an S parameter. Among these, it is known whether or not impedance matching is achieved in S11 representing reflection of port 1 of the S parameter. In the case of the second embodiment, since the impedance Z2 deviates from the center of the Smith chart, S11 takes, for example, a value of several tens of dB.

  By the way, when the plot point Pb of the impedance Z2 is obtained in the Smith chart by the calculation of this example, there is a current situation that the point Pc (see FIG. 6) is also obtained at the symmetrical position on the opposite side of the resistance shaft 32. This Pc corresponds to a frequency point obtained by adding a difference (absolute value) between the multiplied frequency and the approximate multiplied frequency to the multiplied frequency. Therefore, in this example, a process of removing Pc from the determination is required in the impedance matching process.

  Here, FIG. 7 shows a variable range of the variable capacitance diode 22. As can be seen from the figure, the variable range of the variable capacitance diode 22 is a range that slightly overlaps the center of the resistance shaft 32 of the Smith chart. That is, when the variable capacitance diode 22 is varied from the initial value to the maximum value, only the frequency corresponding to the plot point Pb can be output during that time. Accordingly, since the point Pc is excluded from the variable range of the variable capacitance diode 22, only the plot point Pb is extracted without any problem.

According to the configuration of the present embodiment, the following effects can be obtained in addition to (1) to (6) described in the first embodiment.
(7) Even when the multiplication frequency m × fr cannot be obtained from the local oscillator 6, the main antenna 2 side and the receiving circuit 3 side can be matched.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
In the first and second embodiments, as shown in FIG. 8, the matching circuit 4 may be one that performs impedance matching by switching the effective capacitance. In the example shown in FIG. 8, the effective capacitor is switched from Ck1 to Ck2 by switching the switch (FET or the like) 51. In this case, the matching circuit 4 can be a simple circuit.

In the first and second embodiments, the local oscillator 6 is not limited to the PLL system, but may be another system.
-In 1st and 2nd embodiment, the receiver 1 may employ | adopt not only a single super tehrodyne system but a double and a triple, for example. Further, it is not limited to the tehrodyne method.

In the first and second embodiments, the multiplication frequency m × fr is not limited to being generated from the local oscillation frequency fl, but may be generated directly from the reference frequency fbs, for example.
In the first and second embodiments, the multiplication frequency m × fr is not limited to being generated using the local oscillation frequency flo, and a dedicated oscillator for the multiplication frequency m × fr may be provided.

-In 1st and 2nd embodiment, the main antenna 2 is not limited to an inverted L-shaped antenna, For example, you may employ | adopt other antennas, such as a loop antenna.
In the first and second embodiments, the sub antenna 11 is not limited to the pattern antenna, and other antennas can be used.

  In the first and second embodiments, the antenna impedance matching is not necessarily limited to the provision of the dedicated matching circuit 4, and may be performed by adjusting the C component of the receiving circuit, for example.

-In 1st and 2nd embodiment, the frequency of the electromagnetic wave handled with the main antenna 2 or the subantenna 11 can employ | adopt various frequencies.
In the first and second embodiments, the automatic adjustment is not limited to being performed periodically or when the engine is started, and may be performed at any time.

In the first and second embodiments, the configuration of the antenna matching automatic adjustment device 10 is not limited to the configuration described in the embodiment, and may be configured using other circuits.
-In 1st and 2nd embodiment, the antenna matching automatic adjustment apparatus 10 of this example may be applied not only to the receiver 1 but to a transmitter and a transmitter / receiver.

  DESCRIPTION OF SYMBOLS 2 ... Main antenna (antenna), 3 ... Reception circuit which comprises radio circuit, 5 ... Filter which comprises radio circuit, 6 ... Local oscillator, 11 ... Subantenna, 15 ... Directional coupling which comprises adjustment circuit and distributor 16, a filter constituting the adjustment circuit, 17, a detector constituting the adjustment circuit, 20, a substrate, 23, a matching circuit automatic adjustment unit constituting the adjustment circuit and the processing circuit, 33, correction matching as adjustment correction means Z1, Z2 ... impedance, S1 ... received radio wave constituting the radio wave (main radio wave), S2 ... multiplied frequency radio wave constituting the radio wave (radio wave from the sub-antenna), fr ... received frequency as the frequency of the main radio wave, m Xfr: frequency multiplied by frequency of main radio wave, flo: local oscillation frequency constituting oscillation frequency, fbs: reference frequency constituting oscillation frequency, IF: intermediate frequency, Z1, 2 ... impedance.

Claims (7)

A main antenna for communication having an impedance matching function for matching the impedance between the antenna and the radio circuit;
A sub-antenna capable of transmitting a frequency multiplied by a frequency of a main radio wave handled by the main antenna,
An antenna matching apparatus comprising: an adjustment circuit that automatically adjusts impedance matching of the main antenna based on a power level of a radio wave transmitted from the sub antenna among radio waves received by the main antenna. The adjustment circuit includes:
A distributor for distributing and extracting radio waves immediately after passing through the impedance matching function of the main antenna;
A filter that filters only the multiplied frequency that has passed through the distributor;
A detector for detecting the multiplied frequency via the filter;
The antenna matching apparatus according to claim 1, further comprising: a processing circuit that adjusts the impedance matching function based on a power level of a radio wave detected by the detector. 3. The antenna matching apparatus according to claim 1, wherein the frequency of the radio wave transmitted from the sub-antenna is a multiplication of an oscillation frequency used inside the radio circuit. In the case of the super tehrodyne system, the frequency of the radio wave transmitted from the sub-antenna is the multiplication of the local oscillation frequency of the local oscillator of the PLL system necessary for generating the intermediate frequency in the radio circuit, or the oscillation frequency of the local oscillator The antenna matching device according to any one of claims 1 to 3, wherein the antenna matching device is a multiplication of a reference frequency for generating the signal. 5. The antenna matching according to claim 3, further comprising an adjustment correction unit that adjusts the impedance matching while allowing a difference when a radio wave generated from the oscillation frequency is not multiplied by the main radio wave. apparatus. The said adjustment circuit does not start with the frequency of the electromagnetic wave transmitted from the other apparatus, but starts only with the electromagnetic wave transmitted from the said subantenna. Antenna matching device. 2. The main antenna is an inverted L-shaped antenna whose antenna line is substantially L-shaped, and the sub-antenna is a pattern antenna formed on a substrate of the substantially L-shaped antenna. The antenna matching device according to any one of 6.

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