JP2006245755A - Mobile wireless apparatus, and matching circuit selection circuit and matching circuit selection method used for the mobile wireless apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile wireless apparatus the speech quality of which is not deteriorated even when its antenna approaches a user's body. <P>SOLUTION: A frequency mixing circuit 22 mixes a reflected wave f of a transmission wave d made incident onto an antenna 19 with a first oscillation signal (a) to produce a reflection signal g whose frequency F4 (=F2+F1-F1=F2) is the same as that of a second oscillation signal b, and a matching circuit 16 or 17 wherein a level of the reflection wave f is minimized is selected on the basis of a level of a detection output voltage h resulting from detecting the reflection signal g by a comparator 26, a reference voltage source 25 and changeover devices 15, 18. Thus, a maximum transmission output can be obtained at all times and stable speech quality can be obtained. Further, since a single setting of a reference voltage j of the reference voltage source 25 is enough, the configuration of a matching circuit selection section 20 can be comparatively simplified. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a portable radio device, a matching circuit selection circuit and a matching circuit selection method used in the portable radio device, and a state in which call quality deteriorates due to an antenna close to a user's body, such as a mobile phone. And a matching circuit selection circuit and a matching circuit selection method used for the portable radio.

  In recent years, in portable radio devices such as mobile phones, miniaturization of the main body has progressed rapidly, and along with this, antennas tend to be miniaturized. In this trend, when the user is carrying a mobile phone, the antenna is naturally close to the user's body, or the user covers the antenna with his / her hand without being particularly aware of the antenna's position during a call. The call quality may deteriorate. For this reason, a mobile phone has been proposed in which countermeasures against such deterioration of the call quality are taken.

  Conventionally, this type of mobile phone has, as shown in FIG. 2, for example, an oscillator 1, an oscillator 2, a frequency conversion circuit 3, a transmission circuit 4, a switch 5, a matching circuit 6 and a switching circuit. It comprises a device 8 and an antenna 9. The oscillator 1 generates a first oscillation signal a (for example, a frequency F1) that can change to a plurality of types of frequencies. The oscillator 2 always generates the second oscillation signal b having the frequency F2. The frequency conversion circuit 3 frequency-converts the first oscillation signal a and the second oscillation signal b to generate a carrier signal c having a frequency F3 (= F2 + F1), for example. The transmission circuit 4 amplifies the carrier signal c to a specified power and generates a transmission wave d. The switch 5 connects the input side of the matching circuit 6 or the matching circuit 7 and the output side of the transmission circuit 4 based on the switching signal e.

  The matching circuit 6 is composed of a passive element or the like, and transmits the transmission wave d from the transmission circuit 4 to the antenna 9 via the switch 8 and the characteristic impedance so that the antenna 9 has a maximum transmission output in free space. Has been adjusted. The matching circuit 7 is composed of a passive element or the like, transmits the transmission wave d to the antenna 9 via the switch 8, and adjusts the characteristic impedance so that the transmission output is maximized when the antenna 9 is close to the human body. Has been. The switch 8 connects the output side of the matching circuit 6 or the matching circuit 7 and the antenna 9 based on the switching signal e. The antenna 9 radiates the transmission wave d transmitted from the transmission circuit 4 via the switch 5, the matching circuit 6 or the matching circuit 7, and the switch 8.

  In this mobile phone, in a standby state in which it is assumed that the antenna 9 is not close to the human body, the matching circuit 6 is selected based on a switching signal e from a control unit (not shown), and the antenna 9 is close to the human body. It is assumed that the maximum transmission output in each state is obtained by selecting the matching circuit 7 based on the switching signal e in the call state assumed to be present.

In addition to the above-described mobile phone, conventionally, this type of technology has been described in, for example, the following documents.
In the transmission circuit described in Patent Document 1, the input signal is modulated by the modulation circuit, the modulation signal output from the modulation circuit is amplified by the power amplification circuit, and the output of the power amplification circuit is transmitted from the antenna. The modulated signal is demodulated by the demodulation circuit, and the out-of-band component of the input signal included in the demodulated signal is detected by the out-of-band component detection circuit. A control signal is output from the control circuit in response to the out-of-band component detection signal, and the control signal is input to the impedance conversion circuit, and impedance matching between the power amplifier circuit and the antenna is achieved. For this reason, even if the input impedance of the power amplifier circuit changes and a reflected wave is generated in the antenna, impedance matching between the power amplifier circuit and the antenna is achieved, and the gain of the power amplifier circuit is always kept constant. The generation of reflected waves in the antenna is suppressed.
JP-A-8-288864 (abstract, FIG. 1)

However, the above conventional mobile phone has the following problems.
That is, in the mobile phone of FIG. 2, the matching circuit 6 is selected in the standby state and the matching circuit 7 is selected in the call state. However, the antenna 9 is close to a human body or metal even in the standby state. Therefore, there has been a problem that the call quality is deteriorated, for example, the maximum transmission output cannot be obtained and the incoming call cannot be made.

  In the transmission circuit described in Patent Document 1, an out-of-band component of an input signal included in a demodulated signal is detected by an out-of-band component detection circuit, and power amplification is performed based on a control signal corresponding to the out-of-band component detection signal. Impedance matching between the circuit and the antenna is taken. For this reason, the configuration is different from the present invention.

  The present invention has been made in view of the above circumstances, and when the frequency of the first oscillation signal changes by automatically detecting the load state of the antenna and switching the matching circuit with a relatively simple configuration. However, it is an object of the present invention to provide a portable radio device that can always obtain the maximum transmission output and obtain stable call quality.

  In order to solve the above problems, the invention according to claim 1 is characterized in that a first oscillator capable of generating a first oscillation signal having a plurality of types of frequencies and a second oscillation signal having a fixed frequency are always generated. A second oscillator that performs frequency conversion of the first and second oscillation signals to generate a carrier signal, a transmission circuit that amplifies the carrier signal to generate a transmission wave, and the transmission wave And a plurality of matching circuits that transmit the transmission wave from the transmission circuit to the antenna and have characteristic impedances matched in advance corresponding to changes in the impedance of the antenna. According to a portable wireless device provided, a reflected signal of the same frequency as the second oscillation signal is generated by mixing the reflected wave of the transmission wave incident on the antenna and the first oscillation signal, Reflection Based on the level of the matching circuit selection means the level of the reflected wave to select the matching circuit having the minimum from among the respective matching circuits is characterized by being provided.

  A second aspect of the present invention relates to the portable wireless device according to the first aspect, wherein the frequency conversion circuit converts the frequency of the first oscillation signal having the frequency F1 and the second oscillation signal having the frequency F2 to convert the frequency. The carrier signal of F3 (= F2 + F1 or F2-F1) is generated, and the matching circuit selection means has the same frequency F4 (= F2 + F1-F1 = F2 or F2-) as that of the second oscillation signal. F1 + F1 = F2) is generated, and the reflected signal is generated.

  A third aspect of the present invention relates to the portable wireless device according to the first or second aspect, wherein each matching circuit transmits the transmission wave from the transmission circuit to the antenna, and the antenna transmits in free space. A first matching circuit whose characteristic impedance is matched corresponding to the impedance of the antenna so that the output is maximized, and the transmission wave is transmitted to the antenna, and when the antenna is close to the human body, the transmission output A second matching circuit whose characteristic impedance is matched corresponding to the impedance of the antenna so as to be maximized, and the matching circuit selection means detects the reflected wave from the antenna. A frequency mixing circuit for mixing the reflected wave detected by the directional coupler and the first oscillation signal to output the reflected signal, and detecting the reflected signal The first and second matching circuits when the detection output voltage is larger than the reference voltage, and the detection unit that outputs a DC detection output voltage is compared with a reference voltage set in advance. In place of the selected matching circuit, a comparison unit that generates a selection signal for selecting another matching circuit, and the first matching circuit or the second matching circuit are changed according to the selection signal. It is characterized by comprising a selector for selecting.

  According to a fourth aspect of the present invention, there is provided a matching circuit selection circuit, wherein a first oscillator capable of generating a first oscillation signal having a plurality of types of frequencies F1 and a second oscillation signal having a fixed frequency F2 are always provided. A second oscillator to be generated, a frequency conversion circuit for generating a carrier signal of frequency F3 (= F2 + F1, or F2-F1) by frequency-converting the first and second oscillation signals, and amplifying the carrier signal A transmission circuit for generating a transmission wave, a single antenna for radiating the transmission wave, the transmission wave from the transmission circuit to the antenna, and a characteristic corresponding to a change in impedance of the antenna Used in a portable wireless device including a plurality of matching circuits whose impedances are matched in advance, and the first oscillation signal is mixed with the reflected wave of the transmission wave incident on the antenna. A reflected signal having the same frequency F4 (= F2 + F1-F1 = F2 or F2-F1 + F1 = F2) as that of the oscillation signal is generated, and based on the level of the reflected signal, the reflected wave of each of the matching circuits is generated. A feature is that a matching circuit having a minimum level is selected.

  The invention according to claim 5 relates to the matching circuit selection circuit according to claim 4, wherein each of the matching circuits transmits the transmission wave from the transmission circuit to the antenna, and the antenna transmits a transmission output in free space. A first matching circuit whose characteristic impedance is matched corresponding to the impedance of the antenna so as to be maximized, and the transmission wave is transmitted to the antenna, and when the antenna is close to a human body, the transmission output is A directional coupler for detecting the reflected wave from the antenna, and a directional coupler for detecting the reflected wave from the antenna. A frequency mixing circuit that mixes the detected reflected wave and the first oscillation signal to output the reflected signal; and detects the reflected signal to generate a DC detection output voltage. The detection output voltage is compared with a preset reference voltage, and when the detection output voltage is greater than the reference voltage, the first matching circuit and the second matching circuit are selected. In place of the matching circuit, a comparison unit that generates a selection signal for selecting another matching circuit, and a selector that selects the first matching circuit or the second matching circuit by the selection signal It is characterized by being.

  According to a sixth aspect of the present invention, there is provided a matching circuit selection method, wherein a first oscillator capable of generating first oscillation signals having a plurality of types of frequencies F1 and a second oscillation signal having a fixed frequency F2 are always provided. A second oscillator to be generated, a frequency conversion circuit for generating a carrier signal of frequency F3 (= F2 + F1, or F2-F1) by frequency-converting the first and second oscillation signals, and amplifying the carrier signal A transmission circuit for generating a transmission wave, a single antenna for radiating the transmission wave, the transmission wave from the transmission circuit to the antenna, and a characteristic corresponding to a change in impedance of the antenna Used in a portable wireless device including a plurality of matching circuits whose impedances are matched in advance, and the reflected wave of the transmission wave incident on the antenna is mixed with the first oscillation signal to A reflected signal having the same frequency F4 (= F2 + F1−F1 = F2 or F2−F1 + F1 = F2) as that of the Cull signal is generated, and the level of the reflected wave from each of the matching circuits based on the level of the reflected signal It is characterized by selecting a matching circuit that minimizes.

  According to the configuration of the present invention, the matching circuit selection unit mixes the reflected wave of the transmission wave incident on the antenna and the first oscillation signal to generate a reflection signal having the same frequency as the second oscillation signal. The matching circuit that minimizes the level of the reflected wave is selected from the matching circuits based on the level of the reflected signal. Thus, a stable call quality can be obtained. In addition, since the matching circuit is selected based on the level of the reflected signal having the same frequency as that of the second oscillation signal, the configuration of the matching circuit selecting unit can be made relatively simple. In the matching circuit selection means, the frequency mixing circuit mixes the reflected wave of the transmission wave incident on the antenna and the first oscillation signal to generate a reflected signal having the same frequency as the second oscillation signal, Based on the level of the detection output voltage obtained by detecting the reflected signal by the comparison unit and the selector, the matching circuit that minimizes the level of the reflected wave is selected from the matching circuits. For this reason, the maximum transmission output is always obtained, and stable call quality is obtained. Further, since the reflected signal has the same frequency as that of the second oscillation signal, the configuration of the comparison unit is simplified, and the configuration of the matching circuit selection unit can be relatively simplified.

  A plurality of matching circuits whose characteristic impedances are pre-matched in response to changes in the impedance of the antenna are provided, and a matching circuit that detects a reflected wave from the antenna and minimizes the level of the reflected wave is selected. Provided is a portable wireless device that transmits a transmission wave to the same antenna through a selected matching circuit.

FIG. 1 is a block diagram showing an electrical configuration of a main part of a mobile phone according to an embodiment of the present invention.
As shown in the figure, the mobile phone of this example includes an oscillator 11, a local oscillator 12, a frequency conversion circuit 13, a transmission circuit 14, a switch 15, a matching circuit 16, 17, and a switch 18. The antenna 19 and the matching circuit selection unit 20 are configured. The oscillator 11 generates a first oscillation signal a (for example, frequency F1) that can change to a plurality of types of frequencies. The oscillator 12 always generates the second oscillation signal b having the frequency F2. The frequency conversion circuit 13 frequency-converts the first oscillation signal a and the second oscillation signal b to generate a carrier signal c having a frequency F3 (= F2 + F1), for example. The transmission circuit 14 amplifies the carrier signal c to a specified power and generates a transmission wave d. The switch 15 connects the input side of the matching circuit 16 or the matching circuit 17 and the output side of the transmission circuit 14 via the matching circuit selection unit 20 based on the switching signal e from the matching circuit selection unit 20.

  The matching circuit 16 is composed of a passive element or the like, and transmits the transmission wave d from the transmission circuit 14 to the antenna 19 via the switch 18, and the antenna 19 so that the transmission output is maximized in free space. The characteristic impedance is matched to 19 impedances. The matching circuit 17 is composed of a passive element or the like, and transmits the transmission wave d to the antenna 19 via the switch 18, and when the antenna 19 is close to the human body, the transmission output of the antenna 19 is maximized. The characteristic impedance is matched corresponding to the impedance. The switch 18 connects the output side of the matching circuit 16 or the matching circuit 17 and the antenna 19 based on the switching signal e from the matching circuit selection unit 20. The antenna 19 radiates the transmission wave d transmitted from the transmission circuit 14 via the switch 15, the matching circuit 16 or the matching circuit 17, and the switch 18. The matching circuit selection unit 20 mixes the reflected wave of the transmission wave d incident on the antenna 19 and the first oscillation signal a, and has the same frequency F4 as the second oscillation signal b (= F2 + F1-F1 = F2). And a matching circuit with the lowest reflected wave level is selected from the matching circuits 16 and 17 based on the level of the reflected signal.

  In other words, the matching circuit selection unit 20 includes a directional coupler 21, a frequency mixing circuit 22, a resistor 23, a detection diode 24, a reference voltage source 25, and a comparator 26. The directional coupler 21 detects the reflected wave f from the antenna 19 while transmitting the transmission wave d from the transmission circuit 14 to the switch 15. The frequency mixing circuit 22 mixes the reflected wave f detected by the directional coupler 21 with the first oscillation signal a and has the same frequency F4 (= F2 + F1−F1 = F2) as the second oscillation signal b. The reflected signal g is output. The resistor 23 performs impedance matching with respect to the matching circuits 16 and 17 by terminating one of the directional couplers 21. The detection diode 24 detects the reflected signal g and outputs a DC detection output voltage h. In the reference voltage source 25, a reference voltage j is set as a threshold for switching the matching circuits 16 and 17. The comparator 26 compares the detection output voltage h with the reference voltage j of the reference voltage source 25, and when the detection output voltage h is larger than the reference voltage j, the matching circuit selected from the matching circuits 16 and 17 is selected. Instead, a selection signal e for selecting another matching circuit is generated.

Next, processing contents of the matching circuit selection method used in the portable wireless device of this example will be described.
In this portable wireless device, the matching circuit selection unit 20 mixes the reflected wave f of the transmission wave d incident on the antenna 19 and the first oscillation signal, and has the same frequency F4 as the second oscillation signal b (= F2 + F1-F1 = F2) is generated, and a matching circuit that minimizes the level of the reflected wave f is selected from the matching circuits 16 and 17 based on the level of the reflected signal g.

  That is, the first oscillation signal a having the frequency F1 is generated from the oscillator 11, and the second oscillation signal b having the frequency F2 is generated from the oscillator 12. The frequency conversion circuit 13 performs frequency conversion of the first oscillation signal a and the second oscillation signal b, and generates a carrier signal c having a frequency F3 (= F2 + F1). The carrier signal c is amplified to a level commensurate with the prescribed power transmitted from the antenna 19 by the transmission circuit 14, and a transmission wave d is output from the transmission circuit 14. After passing through the directional coupler 21, the transmission wave d is radiated from the antenna 19 through the switch 15, the matching circuit 16 and the switch 18.

  In the matching circuit 16, the characteristic impedance is matched with the impedance of the antenna 19 and the impedance of the directional coupler 21 so that the maximum transmission output can be obtained when the antenna 19 is not close to the human body. At this time, if the antenna 19 is not close to the human body, the matching state is good, and the reflected wave f of the transmission wave d from the antenna 19 is extremely small. The reflected wave f is coupled by the directional coupler 21 and input to the frequency mixing circuit 22. In the frequency mixing circuit 22, the reflected wave f (frequency F3) input from the directional coupler 21 and the first oscillation signal a (frequency F1) from the oscillator 11 are frequency-converted, and a reflected signal g of frequency F4 is output. Is done.

  The reflected signal g is, for example, an intermediate frequency signal having a frequency F4 (= F3-F1 = F2 + F1-F1 = F2). The reflected signal g is converted into a DC detection output voltage h by the detection diode 24 and input to the + side input terminal of the comparator 26. The reference voltage j input to the negative input terminal of the comparator 26 is set to a voltage for switching the matching circuits 16 and 17 according to the magnitude of the reflected wave f, and the selection signal e output from the comparator 26 is When the reflected wave f is small, the level is low (hereinafter referred to as “L”), and when the reflected wave f is large, the level is high (hereinafter referred to as “H”). Therefore, if the matching circuit 16 is selected and the antenna 19 is not close to a human body or the like, the reflected wave f is small and the selection signal e of the comparator 26 is “L”.

  Further, when a human body is brought close to the antenna 19, the impedance of the antenna 19 changes greatly, thereby causing an impedance mismatch with the matching circuit 16, and the reflected wave f becomes large, and the selection signal of the comparator 26 is selected. e becomes "H", the matching circuit 17 is selected by the switches 15 and 18, the matching state becomes good, and the maximum transmission output is transmitted. Therefore, the reflected wave f becomes small and the selection signal e of the comparator 26 becomes “L”. The matching circuit 11 has a characteristic impedance matched with the impedance of the antenna 19 and the impedance of the directional coupler 21 so that the maximum transmission output can be obtained when a human body is close to the antenna 19.

  Further, when the human body changes from the proximity state to the non-proximity state, the reflected wave f increases, so that the selection signal e of the comparator 26 becomes “H” and the matching circuit 16 is selected by the switches 15 and 18. The matching state becomes good, and the maximum transmission output is transmitted from the antenna 19. Further, the frequency F1 of the first oscillation signal a from the oscillator 11 is controlled by the oscillator 11, but is frequency-converted by the frequency mixing circuit 22, so that the reflected signal output from the frequency mixing circuit 22 is used. The frequency of g is always constant, and the matching circuits 16 and 17 are switched regardless of the frequency F1 of the first oscillation signal a.

  As described above, in this embodiment, the frequency mixing circuit 22 mixes the reflected wave f of the transmission wave d incident on the antenna 19 and the first oscillation signal a so as to be the same as the second oscillation signal b. A reflected signal g having a frequency F4 (= F2 + F1−F1 = F2) is generated, and the comparator 26, the reference voltage source 25, and the switches 15 and 18 detect the reflected signal g based on the level of the detected output voltage h. A matching circuit that minimizes the level of the reflected wave f is selected from the matching circuits 16 and 17. For this reason, the maximum transmission output is always obtained, and stable call quality is obtained. In addition, since the setting of the reference voltage j of the reference voltage source 25 may be single, the configuration of the matching circuit selection unit 20 is relatively simple.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiment, and even if there is a design change without departing from the gist of the present invention, Included in the invention.
For example, the matching circuits 16 and 17 are not limited to these two, and three or more matching circuits whose characteristic impedances are matched in accordance with the impedance change of the antenna 19 may be provided. In this case, a switch for selecting one of the three or more matching circuits is provided in place of the switches 15 and 18, and an A / D converter having two or more bits in place of the comparator 26, and It is necessary to provide a decoder for selecting the matching circuit by decoding the output signal of the A / D converter. In the above embodiment, the carrier signal c has the frequency F3 (= F2 + F1) and the reflected signal g has the frequency F4 (= F2 + F1-F1 = F2), but the carrier signal c has the frequency F3 (= F2-F1). The reflected signal g may be set to the frequency F4 (= F2−F1 + F1 = F2).

  The present invention can be applied not only to mobile phones but also to mobile radio devices in general, such as PDAs (Personal Digital Assistants), in which the antenna is likely to be close to the human body and the frequency of the transmission wave can be varied into a plurality of types.

It is a block diagram which shows the electrical constitution of the principal part of the mobile telephone which is an Example of this invention. It is a block diagram which shows the electric constitution of the principal part of the conventional mobile telephone.

Explanation of symbols

11 Oscillator (first oscillator, part of portable radio)
12 Oscillator (second oscillator, part of portable radio)
13 Frequency converter circuit 14 Transmitter circuit 15, 18 selector (part of matching circuit selection means, selector)
16, 17 Matching circuit 19 Antenna 20 Matching circuit selection unit (matching circuit selection means)
21 Directional coupler (part of matching circuit selection means)
22 Frequency mixing circuit (part of matching circuit selection means)
23 Resistance (part of matching circuit selection means)
24 Detection diode (part of matching circuit selection means, detection unit)
25 Reference voltage source (part of matching circuit selection means, part of comparison unit)
26 Comparator (part of matching circuit selection means, part of comparison unit)

Claims (6)

A first oscillator capable of generating first oscillation signals having a plurality of types of frequencies;
A second oscillator that constantly generates a second oscillation signal having a fixed frequency;
A frequency conversion circuit that converts the frequency of the first and second oscillation signals to generate a carrier signal;
A transmission circuit for amplifying the carrier signal to generate a transmission wave;
One antenna for radiating the transmitted wave;
A portable wireless device comprising: a plurality of matching circuits that transmit the transmission wave from the transmission circuit to the antenna and have characteristic impedances matched in advance corresponding to a change in impedance of the antenna;
The reflected wave of the transmission wave incident on the antenna is mixed with the first oscillation signal to generate a reflected signal having the same frequency as the second oscillation signal, and based on the level of the reflected signal, A portable wireless device, comprising: a matching circuit selecting unit that selects a matching circuit that minimizes the level of the reflected wave from the matching circuits. The frequency conversion circuit includes:
The first oscillation signal having the frequency F1 and the second oscillation signal having the frequency F2 are frequency-converted to generate the carrier signal having the frequency F3 (= F2 + F1 or F2-F1).
The matching circuit selection means includes
2. The portable radio according to claim 1, wherein the reflected signal is generated with the same frequency F4 (= F2 + F1-F1 = F2 or F2-F1 + F1 = F2) as the second oscillation signal. Machine. Each matching circuit includes:
A first matching circuit that transmits the transmission wave from the transmission circuit to the antenna and that has a characteristic impedance matched to the impedance of the antenna so that the antenna has a maximum transmission output in free space; ,
The transmission wave is transmitted to the antenna, and includes a second matching circuit whose characteristic impedance is matched corresponding to the impedance of the antenna so that the transmission output is maximized when the antenna is close to the human body. ,
The matching circuit selection means includes
A directional coupler for detecting the reflected wave from the antenna;
A frequency mixing circuit for mixing the reflected wave detected by the directional coupler and the first oscillation signal to output the reflected signal;
A detector for detecting the reflected signal and outputting a DC detection output voltage;
When the detection output voltage is compared with a preset reference voltage and the detection output voltage is greater than the reference voltage, instead of the matching circuit selected from the first and second matching circuits, A comparator for generating a selection signal for selecting another matching circuit;
The portable wireless device according to claim 1 or 2, wherein the portable wireless device includes a selector that selects the first matching circuit or the second matching circuit by the selection signal. A first oscillator capable of generating first oscillation signals of a plurality of types of frequencies F1,
A second oscillator that constantly generates a second oscillation signal having a fixed frequency F2, and
A frequency conversion circuit that frequency-converts the first and second oscillation signals to generate a carrier signal having a frequency F3 (= F2 + F1 or F2-F1);
A transmission circuit for amplifying the carrier signal to generate a transmission wave;
One antenna for radiating the transmitted wave;
The transmission wave from the transmission circuit is transmitted to the antenna, and is used for a portable wireless device including a plurality of matching circuits whose characteristic impedances are matched in advance in response to a change in the impedance of the antenna.
The reflected wave of the transmission wave incident on the antenna and the first oscillation signal are mixed to have the same frequency F4 as the second oscillation signal (= F2 + F1-F1 = F2 or F2-F1 + F1 = F2). The matching circuit is configured to select a matching circuit that generates a minimum reflected wave level from the matching circuits based on the level of the reflected signal. circuit. Each matching circuit includes:
A first matching circuit that transmits the transmission wave from the transmission circuit to the antenna and that has a characteristic impedance matched to the impedance of the antenna so that the antenna has a maximum transmission output in free space; ,
The transmission wave is transmitted to the antenna, and includes a second matching circuit whose characteristic impedance is matched corresponding to the impedance of the antenna so that the transmission output is maximized when the antenna is close to the human body. ,
A directional coupler for detecting the reflected wave from the antenna;
A frequency mixing circuit for mixing the reflected wave detected by the directional coupler and the first oscillation signal to output the reflected signal;
A detector for detecting the reflected signal and outputting a DC detection output voltage;
When the detection output voltage is compared with a preset reference voltage and the detection output voltage is greater than the reference voltage, instead of the matching circuit selected from the first and second matching circuits, A comparator for generating a selection signal for selecting another matching circuit;
5. The matching circuit selection circuit according to claim 4, comprising a selector that selects the first matching circuit or the second matching circuit by the selection signal. A first oscillator capable of generating first oscillation signals of a plurality of types of frequencies F1,
A second oscillator that constantly generates a second oscillation signal having a fixed frequency F2, and
A frequency conversion circuit that frequency-converts the first and second oscillation signals to generate a carrier signal having a frequency F3 (= F2 + F1 or F2-F1);
A transmission circuit for amplifying the carrier signal to generate a transmission wave;
One antenna for radiating the transmitted wave;
The transmission wave from the transmission circuit is transmitted to the antenna, and is used for a portable wireless device including a plurality of matching circuits whose characteristic impedances are matched in advance in response to a change in the impedance of the antenna.
A reflected signal of the same frequency F4 (= F2 + F1-F1 = F2 or F2-F1 + F1 = F2) as the local signal by mixing the reflected wave of the transmission wave incident on the antenna and the first oscillation signal. And selecting a matching circuit that minimizes the level of the reflected wave from the matching circuits based on the level of the reflected signal.

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