JPH0983463A - Digital radio telephone set and hand-free speech headset and microphone used for the telephone set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the speech quality by preventing the generation of noise caused by the intrusion of a transmission wave signal. SOLUTION: Inductors 71, 72 being impedance elements are interposed in series to a position close to a microphone 44 between transmission signal output lines 451, 452 of the microphone 44. The inductors 71, 72 are used to prevent the intrusion of the radio transmission wave signal induced in the transmission signal output lines 451, 452 into the microphone 44.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention employs a time division multiplex transmission system as a wireless transmission system, such as a digital mobile phone and a PHS (Personal Handyphone System) terminal, and a microphone for transmission such as a condenser microphone. The present invention relates to a digital wireless telephone using a high impedance microphone.

[0002]

2. Description of the Related Art In recent years, digital portable telephones and PHS telephones have been widely used. This type of telephone generally employs a time division multiple access (TDMA) system as a wireless access system. In the TDMA method, a radio frequency is time-divided into a plurality of time slots and these time slots are assigned to each communication, and each mobile station transmits a radio signal in the time slot assigned to itself.

FIG. 8 shows a TDMA-TD used in PHS.
6 shows a transmission signal format in the D system. In the figure, one frame (5 msec) of the TDMA-TDD signal includes an uplink for transmitting a signal from a mobile station to a base station and a downlink for transmitting a signal from the base station to each mobile station. And the uplink and the downlink are respectively time-divided into four slots. Then, each pair of the uplink slots R1 to R4 and the downlink slots T1 to T4 is assigned to the mobile device as a radio channel. Therefore, for example, as shown in FIG.
The mobile device to which the radio channel composed of 2, R2 is assigned performs the receiving operation in slot T2 and the transmitting operation in slot R2. Therefore, the transmission / reception operation of the mobile device is intermittently performed in each frame cycle.

On the other hand, since the mobile phone is small,
A condenser type microphone is often used as a microphone for transmission. The condenser microphone is
Since the impedance is high, an active element such as a field effect transistor is generally incorporated for impedance conversion, and the active element is used as a buffer to output a transmission signal.

[0005]

However, when the wireless communication by the above TDMA method is performed using the mobile phone using such a condenser microphone, the following problems may occur.

That is, in a mobile phone, radio waves radiated from an antenna may mix into a signal line of a baseband circuit of the phone due to induction, and the mixed radio frequency signal may enter a microphone. At this time, since the radio frequency signal is transmitted intermittently in the frame cycle of TDMA-TDD as described above, when the radio frequency signal enters the condenser microphone, it is detected by the active element for impedance conversion. TD above
A signal corresponding to the frame frequency of MA-TDD is mixed in the transmission signal. Here, the frame frequency of PHS is 20.
Since it is in the range of 0 Hz and the audible frequency, the frame frequency signal mixed in this transmission signal is output from the telephone of the communication partner as annoying noise, which is a large factor of deterioration of the communication quality, which is not preferable.

The present invention has been made in view of the above circumstances. An object of the present invention is to prevent generation of noise due to mixing of transmitted wave signals, thereby improving the communication quality and a digital radio telephone. It is an object to provide a hands-free call headset and a microphone used in this telephone.

[0008]

In order to achieve the above-mentioned object, the present invention comprises a microphone having an active element for impedance conversion, encodes a transmission signal output from this microphone, and then performs time division. In a digital radio telephone that inserts into a designated time slot in a multiple access frame and transmits by radio, an impedance element is inserted in series with the transmission signal output line of the microphone, and this impedance element induces the transmission signal output line. The wireless transmission signal is prevented from entering the microphone.

Therefore, according to the present invention, even when the TDMA method is used and the condenser microphone is used as the microphone, the transmission wave signal is detected by the active element for impedance conversion and falls into the audible frequency band. The fear that noise is superimposed on the transmitted signal and transmitted is reduced. For this reason, no offensive noise is generated from the telephone set of the other party, whereby the call quality can be maintained high. Further, since it is only necessary to insert the impedance element into the transmission signal output line of the microphone, there is an advantage that it can be realized very easily without fear of complicating and increasing the size of the circuit configuration and further increasing the cost.

In this case, if a circuit board for mounting the microphone is provided separately from the baseband circuit board and the impedance element is mounted on the microphone board, the distance between the impedance element and the microphone is further increased. It is possible to reduce the length of the signal line connecting between them and connecting them, and thus it is possible to more effectively suppress the mixing of noise due to the induced transmission wave into the transmission signal.

Further, if the impedance element is directly attached to the transmission signal output terminal of the microphone or is built in the microphone, the transmission between the impedance conversion active element and the impedance element in the microphone is performed. The signal line length can be made as short as possible, whereby the mixture of transmission wave signals can be suppressed to a minimum and the noise level can be suppressed to a minimum. Furthermore, if the impedance element is of a microphone built-in type, it becomes possible to incorporate the impedance element when manufacturing the microphone, which eliminates the need to separately connect the impedance element when manufacturing the digital wireless telephone. Therefore, it is possible to improve the productivity of the device and provide a cheaper device.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a circuit block diagram showing a configuration of a PHS mobile device which is a first embodiment of a digital radio telephone according to the present invention.

This mobile unit includes a radio unit 1 having an antenna 11, a modem unit 2, a TDMA unit 3, a call unit 4, and
The control unit 5 includes a key input unit 51, a display unit 52, and a sounder 53, and a power supply circuit unit 6 including a battery 61 and an operating voltage generation circuit 62.

That is, a radio frequency signal arriving from a base station (not shown) is received by the antenna 11 and then input to the reception unit 13 via the high frequency switch (SW) 12 of the radio unit 1. In the receiving unit 13, the received radio frequency signal is mixed with a receiving local oscillation signal generated from the frequency synthesizer 14 and frequency-converted into a receiving intermediate frequency signal. The local oscillation frequency generated from the frequency synthesizer 14 is instructed by the control unit 5 according to the radio channel frequency. Further, the radio unit 1 is provided with a reception field strength detection unit (RSSI) 16.
The received electric field strength detection unit 16 detects the received electric field strength of the radio frequency signal coming from the master unit, and the detected value is notified to the control unit 5 for a free channel search or the like.

The received intermediate frequency signal output from the receiver 13 is input to the demodulator 21 of the modem 2. The demodulation section 21 performs digital demodulation of the received intermediate frequency signal, thereby reproducing a digital communication signal.

The TDMA decoding unit 31 of the TDMA unit 3
Extracts a digital communication signal from a time slot allocated to the own device according to an instruction from the control unit 5 and inputs the extracted digital communication signal to the communication unit 4. The call unit 4 uses an adaptive differential PCM transcoder (ADPCM-
TRANSCODER 41 and PCM codec (P
CM-COD) 42, and the digital call signal includes the adaptive differential PCM transcoder 41 and PC.
The M codec 42 sequentially decodes and reproduces an analog call signal. The analog communication signal is amplified by a receiving amplifier (not shown) and then output from the speaker 43.

On the other hand, the transmitted voice input to the microphone 44 is sequentially encoded by the PCM codec 42 and the adaptive differential PCM transcoder 41 to be a digital speech signal. In the TDMA encoding unit 32, the digital speech signal output from the adaptive difference transcoder 41 is inserted into a time slot specified by the control unit 5 and input to the modulation unit 22. In the modulator 22, the carrier signal is digitally modulated by the digital call signal, and the modulated carrier signal is input to the transmitter 15. The modulation method is π / 4 shift QPSK.
(Π / 4 Shifted Quadrature Phase Shift Keying)
Method is used.

In the transmission section 15, the modulated carrier signal is mixed with the transmission local oscillation signal generated from the frequency synthesizer 14 to be frequency-converted to the radio channel frequency instructed by the control section 5, and further predetermined. To the transmit power level of. The radio frequency signal output from the transmitter 15 is the high frequency switch 1
The signal is transmitted from the antenna 11 to the base station (not shown) via 2.

The control unit 5 has, for example, a microcomputer as a main control unit, and is provided with a wireless connection control function associated with incoming and outgoing calls, a call control function corresponding to each of a handset call mode and a hands-free call mode, and the like. There is.

The microphone 44 and its driving circuit are constructed as follows. FIG. 2 is a circuit diagram showing the configuration. The microphone 44 is a condenser microphone, and includes a microphone body 441 and an active element 442 connected to the microphone body 441 and made of a field effect transistor. The active element 442 is a high impedance microphone body 441.
Impedance conversion of the active element 4
A transmission signal is output using 41 as a buffer.

The microphone drive circuit includes a bias resistor 4
53 and 454, and these bias resistors 45
A bias voltage is applied to the microphone 44 by 3,454. Microphone 44 to transmission signal line 45
The transmission signals output to the output terminals 1 and 452 are input to the preamplifier 457 after the direct current components are cut by the stopping capacitors 455 and 456. The preamplifier 457 amplifies the transmission signal to an appropriate level for the PCM codec 42 to encode it.

By the way, the above-mentioned transmission signal lines 451 and 452.
In the vicinity of the microphone 44 of the
Inductors 71 and 72 are inserted in series with 51 and 452. The inductors 71 and 72 are used for the antenna 11
It is intended to prevent the transmission wave signal which is transmitted from the antenna and then induced and mixed into the transmission signal lines 451 and 452 from being input to the microphone 44.

FIG. 3 shows an example of the mounting structure of the inductors 71 and 72.
2 shows a configuration in the case of being arranged in proximity to a baseband circuit board 46 on which each circuit of FIG. Inductor 7
1, 72 are mounted on the baseband circuit board 46. The lead wire 4 is connected to the inductors 71 and 72.
The microphone 44 is connected via 61 and 462.

With such a configuration, even if the transmission wave radiated from the antenna 11 is inductively mixed into the transmission signal lines 451 and 452 on the baseband circuit board 46, the transmission wave signal is transmitted to the inductor 71, It is blocked by 72 and does not enter the microphone 44. Therefore, the problem that the transmission wave signal is detected by the active element 442 in the microphone 44 and the detection signal in the audio frequency band is superimposed on the transmission signal is reduced.

(Second Embodiment) As described above, in the first embodiment, the inductors 71 and 72 are mounted on the baseband circuit board 46 and the inductors 71 and 72 are connected to the inductors 71 and 72 through the lead wires 461 and 462. The case of connecting the microphone 44 has been described.

However, when the microphone 44 and the baseband circuit board 46 are separated from each other, the lead wires 461 and 462 are long, so that the transmission wave radiated from the antenna 11 is transmitted to the lead wire 461. Guided by 462, the transmission wave signal is allowed to enter the microphone 44.

The second embodiment is intended to solve this problem, and has the following mounting structure. FIG. 4 shows the configuration. That is, the microphone 44 and the inductors 71 and 72 are mounted on the microphone board 47 different from the baseband circuit board 46. Then, the inductors 71, 72 of the microphone board 47 and the input terminals of the transmission signal line on the baseband circuit board 46 are connected by lead wires 463, 464.

With such a configuration, the inductor 7
It is possible to further reduce the length of the signal line connecting between the microphones 1 and 72 and the microphone 44 to bring them closer to each other. Therefore, the transmission signal line 45 on the baseband circuit board 46 is
Of course, when the transmitted wave is inductively mixed in 1,452,
Even when the transmission waves are inductively mixed into the lead wires 463 and 464, the signals of these transmission waves are blocked by the inductors 71 and 72 and do not enter the microphone 44. Therefore, it is possible to more effectively suppress the mixing of noise into the transmission signal due to the induced transmission wave.

(Third Embodiment) In this embodiment,
This is a further improvement of the mounting structure of the inductor, in which the inductor is directly attached to or built in the microphone.

FIG. 5 shows an example of the structure. The leads of the inductors 71 and 72 are directly connected to the transmission signal output terminals 443 and 444 of the microphone 44 'by soldering or the like.

With such a configuration, the microphone 4
The connection length between 4'and the inductors 71 and 72 can be further shortened. Therefore, the microphone 44 '
It is possible to more effectively prevent the transmission wave signal from entering the main body.

Further, as shown in FIG. 5, inductors 71, 7
Instead of externally attaching the microphone 2 to the microphone 44, the microphone 2 may be housed in the microphone 44 '. In this case, inductors 71, 72 may be connected between the transmission signal output terminals 443, 444 and the active element 442 in the microphone 44 '. With this configuration, although the microphone 44 'becomes slightly larger, it is possible to further enhance the effect of preventing the intrusion of the guided transmission wave signal.

(Fourth Embodiment) In this embodiment,
Instead of providing an inductor, a lead wire connecting between the microphone and the baseband circuit board is passed through a ferrite core to prevent the inductive transmission wave signal from entering the microphone.

FIG. 6 shows the structure thereof. Lead wires 465 and 466 connecting between the microphone 44 and the baseband circuit board 46 are passed through the ferrite cores 73 and 74. As a result, the ferrite cores 73 and 74 exhibit the same function as the inductor, and the microphone 44
The intrusion of the induced transmission wave signal into the is prevented.

(Fifth Embodiment) Some mobile phones are equipped with a headset for hands-free communication so that a user can talk without holding the phone. The headset is equipped with a hands-free microphone and speaker. When making a hands-free call, the call mode selection switch provided on the telephone is operated to switch from the handset call mode to the hands-free call mode. Then, the call path selector switch in the telephone is switched, whereby the microphone and speaker of the above headset are connected to the PCM codec instead of the microphone and speaker for handset communication, enabling hands-free communication using the headset. Become.

By the way, an electret condenser type microphone is often used for the microphone of this headset, and therefore, the problem of noise generation due to intrusion of the inductive transmission wave similarly occurs. This embodiment is intended to solve this problem.

That is, as shown in FIG. 7, the hands-free speaker 81 and the hands-free microphone 82 are
Connection plug 85 through connection cords 83 and 84, respectively
It is connected to the. Among them, inductors 75 and 76 are provided between the connection cord 83 and the hands-free microphone 82.
Are inserted in series.

With this configuration, even when a hands-free call is made using the headset, the inductive transmission wave is prevented from entering the hands-free microphone 82, and a high-quality call with less noise can be made. It becomes possible to do it.

The present invention is not limited to the above embodiments. For example, although the inductors 75 and 76 are inserted in the signal line in the fifth embodiment, the signal line may be passed through the ferrite core similarly to the fourth embodiment.

As the impedance element for blocking the induced transmission wave, a resistor may be used in addition to the inductive element such as the inductor and the ferrite core. In addition, the insertion position and connection structure of the impedance element for blocking the inductive transmission wave, the shape and configuration of the microphone, the type and configuration of the digital wireless telephone, the wireless transmission system, etc. are variously modified without departing from the scope of the present invention. Can be implemented.

[0041]

As described above in detail, according to the present invention, the impedance transmission is inserted in series in the transmission signal output line of the microphone, and the impedance transmission element induces the wireless transmission signal in the transmission signal output line of the microphone. Is configured to prevent the intruder from entering the microphone.

Therefore, according to the present invention, it is possible to prevent the generation of noise due to the mixture of the transmitted wave signals, and thereby improve the call quality, and the hands-free call head used in this telephone. A set as well as a microphone can be provided.

[Brief description of drawings]

FIG. 1 is a first digital radio telephone according to the present invention.
3 is a circuit block diagram showing the embodiment of FIG.

FIG. 2 is a circuit diagram showing a configuration of a microphone and its drive circuit in the wireless telephone shown in FIG.

FIG. 3 is a perspective view showing a mounting structure of the microphone and the drive circuit shown in FIG.

FIG. 4 is a perspective view showing a mounting structure of a microphone and its drive circuit according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing a configuration of a microphone according to a third embodiment of the present invention.

FIG. 6 is a perspective view showing a mounting structure of a microphone and a drive circuit thereof according to a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a configuration of a headset according to a fifth embodiment of the present invention.

FIG. 8 is a diagram showing an example of a transmission format of the TDMA-TDD system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Radio part 11 ... Antenna 12 ... High frequency switch (SW) 13 ... Reception part 14 ... Frequency synthesizer 15 ... Transmission part 16 ... Received electric field strength detection part (RSSI) 2 ... Modem part 21 ... Demodulation part 22 ... Modulation part 3 ... TDMA unit 31 ... TDMA decoding unit 32 ... TDMA encoding unit 4 ... Calling unit 41 ... Adaptive difference PCM transcoder (ADPCM-T)
RANCODER 42 ... PCM codec 43 ... Speaker 44, 44 '... Microphone 441 ... Microphone body 442 ... Active element 443, 444 ... Transmission signal output terminal 451, 452 ... Transmission signal line 453, 454, ... Bias resistance 455, 456 ... Stopping capacitor 457 ... Preamplifier 46 ... Baseband circuit board 461, 462, 463, 464, 465, 466 ... Lead wire 47 ... Microphone board 71, 72, 85, 76 ... Inductor 73, 74 ... Ferrite core 81 ... Hands-free speaker 82 ... Hands-free microphone 83,84 ... Connection cord 85 ... Connection plug

Front Page Continuation (72) Inventor Oyama Dai 1-share company at 3-1, Asahigaoka, Hino-shi, Tokyo Inside the Toshiba Hino factory (72) Inventor Tomoyuki Taniguchi 1-share company, 3-chome, Asahigaoka, Hino-shi, Tokyo Toshiba Hino Factory

Claims (6)

[Claims] 1. A microphone having an active element for impedance conversion is provided, and a transmission signal output from this microphone is encoded by an encoding unit and then inserted into a designated time slot in a time division multiple access frame. In a digital wireless telephone that wirelessly transmits by radio, an impedance element for preventing the wireless transmission wave signal induced in the transmission signal output line from entering the microphone is connected in series to the transmission signal output line of the microphone. A digital wireless telephone characterized by being inserted. 2. A second circuit board, which is connected via a signal line to a first circuit board that constitutes a baseband circuit including the encoding section, and the microphone and the second circuit board are provided on the second circuit board. The digital radio telephone according to claim 1, wherein an impedance element is mounted. 3. The digital radio telephone according to claim 1, wherein the impedance element is directly attached to a transmission signal output terminal of a microphone. 4. The digital radio telephone according to claim 1, wherein the impedance element is connected between the active element and a transmission signal output terminal in a microphone housing. 5. A speaker and a microphone having an active element for impedance conversion are provided, and the speaker and the microphone are connected to a digital wireless telephone that performs wireless transmission in a time division multiplex system via a connection cord. In a hands-free call headset to be used, an impedance element for preventing a wireless transmission signal induced in the transmission signal output line from entering the microphone is connected in series to the transmission signal output line of the microphone. A headset for hands-free calling, which is characterized by being inserted. 6. A microphone provided as a transmitter in a digital radio telephone that inserts a transmission signal into a designated time slot in a time-division multiple access frame and wirelessly transmits, and an active element for impedance conversion in a transmission signal path. And in the transmission signal path between the active element and the transmission signal output terminal, the induction signal of the transmission wave wirelessly transmitted from the digital radio is sent to the active element via the transmission signal path. A microphone characterized in that an impedance element for preventing intrusion is inserted in series.