JPH09116457A - Impedance matching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain impedance matching without an influence from a human body even in the case that a user carries a radio machine to speak near his human body and to improve the convenience for use. SOLUTION: When the off-hook state is detected by an off-hook detection circuit 3 and it is detected by a hands free detection circuit 4 that a hands free function is not used, a DC current is inputted from a DC current generation circuit 5 to a switch circuit 6. By input of the DC current, the switch circuit 6 connects a correction circuit 7 and a matching circuit 2. This correction circuit 7 consists of a capacitor or a coil to suppress impedance mismatching between an antenna 1 and a radio part due to an influence of the human body of the user.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impedance matching device, and more particularly to an antenna impedance matching device used in a radio device.

[0001]

2. Description of the Related Art Conventionally, this type of antenna impedance matching device has been used for the purpose of impedance matching between an antenna and a radio section connected to the latter stage of the antenna.

However, when a wireless device is carried near the human body of a user to carry out a call, since the human body is a kind of conductor, there is a problem that mismatching occurs in impedance matching between the antenna and the wireless unit. is there.

As a means for solving this kind of problem, for example, a portable radio device described in Japanese Patent Laid-Open No. 3-141730 is known.

FIG. 6 is a schematic view of the radio device described in the publication.

In FIG. 6, the radio device includes a loop antenna 13, a choke coil 14 and a diode 15 connected to one end of the loop antenna 13, a variable capacitor 16 for tuning the loop antenna 13, and a loop antenna 13. And a transmission / reception unit 11 that is connected to and performs transmission / reception of data and comparison of data or signal levels. The loop antenna 13 is integrally formed with the battery, the sounding body, or the metal diaphragm 12.

When the radio device is used away from the human body of the wearer, a direct current is conducted to the diode 15 via the choke coil 14 and the loop antenna 1
On the other hand, when the wireless device is carried near the human body of the wearer and used, the loop antenna 13 is affected by the human body.
Since a mismatch occurs in the impedance matching between the transmission / reception unit 11 and the transmission / reception unit 11, the conduction of the direct current through the choke coil 14 to the diode 15 is stopped and the loop antenna is made non-conduction. At this time, the battery, the sounding body, or the metal diaphragm 12 formed integrally with the loop antenna 13 is electrically coupled to the human body to form a dipole antenna.

[0007]

However, in this portable wireless device, the user has to switch the loop antenna to conductive or non-conductive depending on whether or not the wireless device is carried, so that it is inconvenient. there were.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an impedance matching device that performs impedance matching and improves convenience even when a wireless device is carried near the human body of a user and a call is made.

[0009]

In order to achieve the above-mentioned object, an impedance matching device according to the present invention comprises a matching means for matching impedance between an antenna and a radio section connected to the latter stage of the antenna, and a radio device. When detecting that the wireless device is making a call near the human body of the user and detecting that the detecting means is making a call,
Correction means for correcting the impedance of the matching means.

By adopting such a configuration, when the wireless device is carried near the human body of the user for a call, it is detected by the detecting means, and by this detection, the correcting means corrects the impedance of the matching means. Therefore, it is possible to achieve impedance matching between the antenna and the wireless unit despite the influence of the human body.

Further, since the detecting means detects a call near the human body of the user of the radio,
Since it is not necessary to select whether or not the call is in the vicinity of the human body and operate the wireless device, convenience can be improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a functional block diagram showing an embodiment of an impedance matching device according to the present invention.

In FIG. 1, the impedance matching device includes an antenna 1, a matching circuit 2, an off-hook detecting circuit 3, a hands-free detecting circuit 4, and a direct current generating circuit 5.
A switch circuit 6, a correction circuit 7, and a wireless unit 8.

In this matching device, when receiving a radio signal from a partner radio (not shown), the radio signal is received by the antenna 1 and the received signal is output to the matching circuit 2. The matching circuit 2 is for impedance matching between the antenna 1 and the wireless unit 8, and the received signal is output to the wireless unit 8 via this matching circuit 2. The received signal is demodulated after being amplified and frequency-converted in the wireless section 8.

On the other hand, when the transmission signal is transmitted to the partner radio, the transmission signal modulated and amplified by the radio section 8 is output to the matching circuit 2. Then, the transmission signal is output to the antenna 1 via the matching circuit 2. Antenna 1 is
This transmission signal is transmitted to the partner radio.

Since the details of the circuit configuration of the latter stage of the radio section 8 and their operations are not directly related to the present invention, their explanations are omitted.

The off-hook switch detection circuit 3 detects whether or not the wireless device is in a call state. For example, in a mobile phone or the like, it is detected whether or not the off-hook state. When the off-hook state is detected, the off-hook switch detection circuit 3 outputs a high-level off-hook detection signal to the DC current generation circuit 5. The hands-free detection circuit 4 is used, for example, when a mobile phone or the like has a hands-free function, and when it is detected that a hands-free call is being made, a high-level hands-free detection is performed. The signal is output to the DC current generation circuit 5. It should be noted that the hands-free call is a call performed without using the handset of the mobile phone, and the mobile phone is used away from the human body of the wearer at this time. And
In a hands-free call, a microphone that inputs the voice of the carrier and a speaker that outputs the voice of the other party are used.

The DC current generating circuit 5 receives the high level off-hook detection signal from the off-hook detecting circuit 3,
Moreover, when the high level hands-free detection signal from the hands-free detection circuit 4 is not input, a DC current is output to the switch circuit 6.

The switch circuit 6 connects the matching circuit 2 and the correction circuit 7 when the direct current from the direct current generating circuit 5 is input. The correction circuit 7 is composed of a capacitor or a coil, and the other end is grounded.

Next, one embodiment of the circuit of the matching circuit 2 is shown in FIG.
This will be described with reference to FIG.

In FIG. 2, the matching circuit 2 is a π-type matching circuit including capacitors 21 and 23 and a coil 22. The matching circuit 2 achieves impedance matching between the antenna 1 and the radio unit by the combined impedance of the capacitors 21 and 23 and the coil 22.

Next, an embodiment of the circuit of the DC current generating circuit 5 will be described with reference to FIG.

In FIG. 3, the direct current generating circuit 5 has a resistor 51 having one end connected to the off-hook detection circuit 3 and a transistor 5 having a base connected to the other end of the resistor 51.
3 and the transistor 5 with one end connected to the other end of the resistor 51
3 has a resistor 54 having the other end connected to the emitter, and the DC current generating circuit 5 has a resistor 52 having one end connected to the hands-free detection circuit 4 and a base connected to the other end of the resistor 52. The collector of which is connected to the emitter of the transistor 53, the emitter of which is grounded, and the resistor 56 whose one end is connected to the other end of the resistor 52 and whose other end is connected to the emitter of the transistor 54.
And. Further, in the direct current generating circuit 5, a base of the transistor 53 is connected to the collector of the transistor 53, the collector is connected to the power supply voltage VDD, and the collector of the transistor 53 is connected to the power supply voltage VDD at one end. Resistor 57 and transistor 58
A resistor 59 whose one end is connected to the emitter of and the other end is connected to the switch circuit 6.

In the direct current generating circuit 5, when a high level off-hook detection signal from the off-hook detection circuit 3 is input to the base of the transistor 53 via the bias resistor 51, the transistor 53 is turned on. On the other hand, when a high-level handsfree detection signal is input from the handsfree detection circuit 4 to the base of the transistor 55 via the bias resistor 52, the transistor 55 is turned on.

Therefore, when a high level off-hook detection signal is input from the off-hook detection circuit 3 to the DC current generating circuit 5 and a high-level hands-free detection signal is input from the hands-free detection circuit 4 to the DC current generating circuit 5, Both transistors 53 and 55 are turned on.
At this time, a direct current from the power supply voltage VDD flows into the ground via the resistor 57, so that the bias voltage applied to the base terminal of the transistor 58 becomes low level. When the bias voltage applied to the base terminal of the transistor 58 becomes low level, the transistor 58 is turned off, so that the direct current is not output to the switch circuit 6.

On the other hand, when the off-hook detection signal from the off-hook detection circuit 3 is input to the DC current generation circuit 5 and the hands-free detection signal from the hands-free detection circuit 4 is not input to the DC current generation circuit 5, the transistor 53 is turned on. Then, the transistor 55 is turned off. Therefore, a bias from the power supply voltage VDD is applied to the base terminal of the transistor 58 by the resistor 57 and the transistor 58 is turned on, so that a direct current is output to the switch circuit 6.

When the off-hook detection signal is not input to the DC current generating circuit 5 and the hands-free detection signal is input to the DC current generating circuit 5, the transistor 53 is turned off and the transistor 55 is turned on. Therefore, the base terminal of the transistor 58 is opened, the bias voltage becomes low level, and the transistor 58 is turned off, so that the direct current is not output to the switch circuit 6.

Further, unless the off-hook detection signal is input to the DC current generating circuit 5 and the hands-free detection signal is not input to the DC current generating circuit 5, both the transistors 53 and 55 are turned off. The terminal is opened and the bias voltage becomes low level. When the bias voltage applied to the base terminal of the transistor 58 becomes low level, the transistor 58 is turned off, so that the direct current is not output to the switch circuit 6.

Therefore, the DC current is switched only when the DC current generation circuit 5 inputs the high-level off-hook detection signal from the off-hook detection circuit 3 and does not input the high-level hands-free detection signal from the hands-free detection circuit 4. It is output to the circuit 6.

Next, an embodiment of the circuit of the switch circuit 6 will be described with reference to FIG.

In FIG. 4, the switch circuit 6 has a capacitor 61 having one end connected to the direct current circuit 5 and the other end grounded, a coil 62 having one end connected to one end of the capacitor 61, and another coil 62. The anode is connected to the end,
Pin diode 63 whose cathode is connected to the correction circuit 7
And.

In the switch circuit 6, the pin diode 63 becomes conductive when a direct current is applied. Therefore, when the DC current from the DC current generating circuit 5 is input to the switch circuit 6, the high frequency component is blocked by the capacitor 61 and the coil 62, and the pin diode 63 becomes conductive. At this time, the matching circuit 2 and the correction circuit 7 are connected. The capacitor 61 and the coil 62 also have a function of preventing a received signal from the matching circuit 2, that is, an AC signal from flowing into the DC current generating circuit 5.

On the other hand, when the direct current from the direct current circuit 5 is not input to the switch circuit 6, the pin diode 63 becomes non-conductive, so that the matching circuit 2 and the correction circuit 7 are opened.

Next, the operation of the impedance matching device shown in FIG. 1 will be described.

In FIG. 1, since the call is started,
When the user puts the mobile phone in the off-hook state, the off-hook detection circuit 3 detects the off-hook state and outputs a high-level off-hook detection signal to the DC current circuit 5. On the other hand, when the user puts the mobile phone in the hands-free state because the hands-free call is started, the hands-free detection circuit 4 detects the hands-free state, and the high-level hands-free detection signal is the direct current circuit. 5 is output. When these signals are input, the direct current circuit 5 does not output a direct current, and therefore the switch circuit 6 opens the matching circuit 2 and the correction circuit 7.
At this time, since the wireless device is not used in the vicinity of the carrier, the correction circuit 7 does not correct the matching circuit 3.

On the other hand, when the mobile phone is put into the off-hook state, the off-hook detection circuit 3 outputs an off-hook detection signal to the direct current circuit 5, and when the hands-free communication is not performed, the hands-free detection circuit 4 detects the hands-free. No signal is output to the direct current circuit 5. The direct current circuit 5 outputs a direct current, so that the switch circuit 6
Thus, the matching circuit 2 and the correction circuit 7 are connected. At this time, since the radio is used near the wearer,
The matching circuit 3 is corrected by the correction circuit 7.

When the call is not started, the mobile phone is not put into the off-hook state, so that the off-hook detection circuit 3 does not output the off-hook detection signal to the direct current circuit 5. At this time, since the direct current circuit 5 does not always output the direct current, the switch circuit 6 opens the matching circuit 2 and the correction circuit 7. Therefore, the correction circuit 7 does not correct the matching circuit 3.

As described above, when the wireless device, for example, a mobile phone is used near the human body of the user, that is, when it is in the off-hook state and the hands-free call is not made, the matching circuit is switched by the switch circuit 6. 2 and the correction circuit 7 are connected to correct the impedance matching mismatch between the antenna 1 and the wireless unit 8.

The correction of the impedance matching mismatch between the antenna 1 and the radio section will be described in detail with reference to FIGS. 5 (a) and 5 (b).

FIG. 5A is a diagram showing the return loss due to the antenna and the radio section when the impedance matching device according to the present invention is not used.

In FIG. 5A, the call is not started,
When in the standby state, as indicated by the solid line in the figure, the transmission frequency band and the reception frequency band are located near the resonance frequency A between the antenna 1 and the radio unit, and the return between the antenna 1 and the radio unit is returned. There is little loss, and impedance matching between the two is achieved.

On the other hand, when the call is started and the hands-free call is not used, the resonance frequency B between the antenna 1 and the radio section 8 is affected by the human body of the user as shown by the dotted line in the figure. The frequency shifts to the low range. Therefore, the return loss between the antenna 1 and the wireless unit 8 becomes large, and impedance matching between the antenna 1 and the wireless unit 8 cannot be achieved. In this case, in particular, the reception sensitivity is deteriorated and the call is hindered.

FIG. 5B is a diagram showing the return loss due to the antenna and the radio section when the impedance matching device according to the present invention is used.

In FIG. 5B, the call is not started,
When in the standby state, as indicated by the solid line in the figure, the transmission frequency band and the reception frequency are in the vicinity of the resonance frequency C (the same frequency as the resonance frequency A) between the antenna 1 and the radio unit, as in FIG. 5A. Band 1 is located and antenna 1
And the return loss with the radio unit is reduced, and impedance matching between the two is achieved.

On the other hand, even when the call is started and the hands-free call is not used, that is, even if the influence of the human body of the user is received, the impedance matching between the antenna 1 and the radio section is corrected by the correction circuit. Because
As indicated by the dotted line in the figure, the shift of the resonance frequency D between the antenna 1 and the radio unit to the low frequency band becomes small. Therefore, the transmission frequency band and the reception frequency band are located in the vicinity of the resonance frequency D, the return loss between the antenna 1 and the radio section is reduced, and impedance matching between the two is achieved.

The deviation of the resonance frequency between the antenna 1 and the radio section due to the influence on the human body of the user has a capacitive property and a dielectric property, which are determined by the type or structure of the antenna. For example, in the case of a whip antenna, the inductance is equivalent to a circuit in which the inductance is connected in series under the influence of the human body of the user. Therefore,
In this case, the deviation of the resonance frequency between the antenna 1 and the radio section becomes dielectric, so that the correction circuit 7 is capacitive, that is, composed of a capacitor.

As described above, whether the capacitance or the dielectric property of the antenna and the radio section when the resonance frequency is shifted is determined by the type or structure of the antenna. The configuration is determined.

In the above-described embodiment, whether or not the wireless device is used near the human body of the user is explained by detecting the off-hook state and the use or non-use of the hands-free function by taking the mobile phone as an example. However, the present invention is not limited to these. Therefore, in the present invention, any means may be used as long as a means for detecting whether or not the wireless device is used near the human body of the user is used. Of course, only the off-hook state or the use state of the hands-free function may be detected.

[0050]

As described above, in the impedance matching device according to the present invention, when the radio is used near the human body of the user, the impedance between the antenna and the radio unit is mismatched due to the influence of the human body. Since the means for correcting the impedance is provided, it is possible to suppress the mismatch between the impedances of the both.

Further, the means for detecting whether or not the radio device is used near the human body of the user is not operated by the user but is automatically detected, so that the convenience of use is improved. be able to.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an impedance matching device showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of the matching circuit shown in FIG.

FIG. 3 is a circuit diagram showing an example of the DC current generating circuit shown in FIG.

FIG. 4 is a circuit diagram showing an example of a switch circuit shown in FIG.

FIG. 5 is a diagram for explaining correction of mismatching of impedance matching between an antenna and a wireless unit.

FIG. 6 is a schematic diagram of a conventional impedance matching device.

[Explanation of symbols]

 1 ・ ・ ・ Antenna 2 ・ ・ ・ Matching circuit 3 ・ ・ ・ Off-hook detection circuit 4 ・ ・ ・ Hands-free detection circuit 5 ・ ・ ・ DC current generation circuit 6 ・ ・ ・ Switch circuit 7 ・ ・ ・ Correction circuit 11 ・ ・ ・Transmitter / receiver 12 ・ ・ ・ Battery or sounding body or vibrator 13 ・ ・ ・ Loop antenna 14 ・ ・ ・ Choke coil 15 ・ ・ ・ Diode 16 ・ ・ ・ Variable capacitor 21 ・ ・ ・ Capacitor 22 ・ ・ ・ Coil 23 ・ ・ ・Capacitor 51, 52, 54, 56, 57, 59 ... Resistor 53, 55, 58 ... Transistor 61 ... Capacitor 62 ... Coil 63 ... Pin diode

Claims (8)

[Claims] 1. A matching means for matching impedance between an antenna and a wireless unit connected to the latter stage of the antenna, and detecting that the wireless device is talking near the human body of the user of the wireless device. An impedance matching device comprising: a detection unit; and a correction unit that corrects the impedance of the matching unit when the detection unit detects that a call is being made. 2. The detecting means outputs a detection signal when detecting that the wireless device is talking, and the correcting means corrects the impedance of the matching means when the detecting signal is input. The impedance matching device according to claim 1, wherein: 3. The correction means includes a switch circuit which is turned on / off by the input of the detection signal, and a capacitor or a coil, and is connected to the matching circuit when the switch means is turned on. The impedance matching device according to claim 2, further comprising: 4. The switch circuit, a capacitor having one end grounded and the other end connected to the detection means, a coil having one end connected to the other end of the capacitor, one end connected to the correction circuit, The impedance matching device according to claim 3, further comprising: a pin diode having the other end connected to the other end of the coil and the matching means. 5. The impedance matching device according to claim 1, wherein the wireless device is a mobile phone. 6. An off-hook detection unit that outputs an off-hook detection signal when the mobile phone is in an off-hook state, and a hands-free detection signal when a hands-free function is used for a call of the mobile phone. 6. A hands-free detecting means for outputting the above, and a direct current generating means for inputting the off-hook detection signal and outputting a direct current when the hands-free detection signal is not input. The impedance matching device described. 7. The direct current generating means, wherein a base terminal is connected to a first resistor for generating a bias voltage by the off-hook detection signal, and a negative feedback is applied by a second resistor connected to an emitter terminal. The base terminal is connected to the first transistor and the third resistor that generates a bias voltage by the handsfree detection signal, the emitter terminal is grounded, and the fourth resistor connected to the emitter terminal provides negative feedback. A second transistor connected to the first transistor, an emitter terminal of the first transistor and a base terminal connected to one end of a fifth resistor, and a collector terminal connected to a DC power supply voltage and the other end of the fifth resistor. And a third transistor whose emitter terminal is connected to the correction means via a sixth resistor. Impedance matching device as claimed. 8. The impedance matching device according to claim 1, wherein the matching circuit is a π-type matching circuit including at least two capacitors and at least one coil.