WO2004086814A1

WO2004086814A1 - Echo prevention circuit

Info

Publication number: WO2004086814A1
Application number: PCT/JP2004/003495
Authority: WO
Inventors: Yasutoshi Taniguchi
Original assignee: Nap Enterprise Co., Ltd.; School Juridical Person Of Fukuoka Kogyo Daigaku
Priority date: 2003-03-25
Filing date: 2004-03-16
Publication date: 2004-10-07
Also published as: JP2004297185A; TW200503574A

Abstract

An echo prevention circuit is configured in such a manner that in a telephone receiving part (11) of one communication device (1), second amplifiers (A2,A3) connected to respective speakers (SP1,SP2) are provided separately from an amplifier circuit (A1) and that a distributing circuit (12) is provided for distributing, to these second amplifiers, the magnitude of a telephone reception signal voltage, which has been supplied from a transmission system (18) and amplified by the amplifier, in an unbalanced manner at any time such that an output voltage of a microphone (MIC1) is minimum. This prevents echo effect from occurring between the telephone receiving and transmitting parts of each of two communication devices (1,2), so that the telephone receiving and transmitting parts can be located at the same place or close places and a stable two-way telephone communication can be realized.

Description

Description Echo prevention circuit Technical field

The present invention relates to mobile telephones and other general mobile telephones, general telephones, microphones in general, translators, loudspeakers for the deaf and vocal cord injured, communicators for travel guides, The present invention relates to an echo prevention circuit that is incorporated in various communication devices such as a communication device for an announcer, a communication device for a conductor of a train, and a headset for an operator, and is effective in preventing echo of these communication devices. Background art

Conventionally, wired and wireless slave units used for mobile communication such as mobile phones have been known as communication devices. From the slave unit, a master unit and a transmission unit including a telephone radio wave relay unit are transmitted. A device that performs two-way communication with a communication device on the other end has been proposed (for example, Japanese Patent Application Laid-Open No. 2002-304007)

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This is composed of a transmitting unit including an amplifier and a microphone for transmitting a signal such as voice by one communication device, a speaker or earphone that receives information, and a receiving unit including an amplification circuit, and the other communication device It consists of a transmission unit including a similar microphone and amplifier circuit, and a receiver unit including a speaker or earphone and amplifier circuit, and these two communication devices are connected via a transmission system to enable two-way communication. I have.

By the way, in the case of the two-way communication, a loop is formed by electrical coupling including sound waves and the like transmitted through the space of the transmitting / receiving section of both communication devices, and the oscillation phenomenon occurs. Pico phenomenon may occur. At this time, the oscillation phenomenon

-When the loop gain is 1 or more, and the echo phenomenon occurs when the loop gain of electrical coupling is 1 or less, the transmitter and receiver are integrated. At present, it is not possible, and it will be a major problem in both noise reduction and miniaturization, weight reduction and manufacturing cost reduction of communication equipment in both wired and wireless communication.

Therefore, the present invention solves the above-mentioned conventional problems, and causes no oscillation phenomenon and no echo phenomenon between the transmitting / receiving section between the two communication devices, so that the transmitting section and the receiving section do not occur. It is an object of the present invention to provide an echo prevention circuit that can be installed at or close to a device and that can perform stable two-way communication. Disclosure of the invention

In order to achieve the above object, an echo prevention circuit according to the present invention includes a microphone for transmitting a signal such as voice by one communication device, a transmitting section including an amplifier circuit, a speaker or earphone for receiving information, and an amplifier circuit. The other communication device is composed of a transmission unit including a similar microphone and an amplification circuit, and a reception unit including a speaker or an earphone and an amplification circuit. A plurality of speakers or earphones are installed in a receiver of one of the communication devices, and these speakers or earphones are connected to the second A plurality of amplifiers are provided separately from the amplifier circuit. The magnitude of the signal voltage is such that the magnitude of the received signal voltage applied to one amplifier circuit is not equal to the magnitude of the received signal voltage applied to the other amplifier circuit, and the output voltage of the microphone is always unbalanced. A distribution circuit that distributes and sets the minimum is installed. I do.

According to the present invention, the echo phenomenon does not occur between the transmission and reception units of both communication devices, and the transmission unit and the reception unit can be provided together or in close proximity. In addition, there is no need to disconnect the transmitting and receiving sections to prevent echo, and to perform complicated daisy-mail operations such as computer processing, etc. It is a breakthrough that can be made possible. In addition, the manufacturing cost can be kept relatively low due to the simple configuration, and the size and weight can be reduced.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of an echo prevention circuit incorporated in a communication device capable of two-way wireless communication shown as an embodiment of the present invention. FIG. 2 is a block diagram of an echo prevention circuit shown as another embodiment. FIG. 3 is an enlarged block diagram of the echo prevention circuit according to the first embodiment. FIG. 4 is a schematic diagram in which two spikes or an earphone and a microphone are hermetically incorporated. BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference to the accompanying drawings. This embodiment is applied to a communication device (for example, a mobile phone) capable of two-way wireless communication.

In FIG. 1, components that are not necessary for explanation, such as batteries for operating the circuit, are omitted. The receiver 11 of the communication device 1 is composed of an amplification circuit A1, a distribution circuit 12 composed of a variable resistor, a pair of amplification circuits A2 and A3, and a pair of speeds SP1 and SP2. I have. The transmitter 13 is a microphone It consists of an on-MIC1 and an amplifier circuit A4. The receiver 15 of the communication device 2 includes an amplification circuit A5, a distribution circuit 16 composed of variable resistors, a pair of amplification circuits A6 and A7, and a pair of speakers 3P3 and SP4. ing. The transmitting section 17 includes a microphone MIC 2 and an amplification circuit A8. Reference numeral 18 denotes a transmission system that connects both communication devices 1 and 2.

In the distribution circuit 12, the magnitude of the reception signal voltage supplied to the amplifiers A2 and A3 is such that the magnitude of the reception signal voltage supplied to the amplification circuit A2 is equal to the magnitude of the reception signal voltage supplied to the amplification circuit A3. Instead, it is set by manually adjusting the variable resistance so that it is always unbalanced. At the same time, the distribution is akAti so that the output voltage of the microphone MIC1 is also minimized.

In the communication device 1 as described above, a reception signal transmitted from the communication device 2 through the transmission system 18 in the reception unit 11 is received by the distribution circuit 12 from the amplifier A 1 to the amplifiers A 2 and A 3. The signal voltage is adjusted and input. Then, the amplifiers A2 and A3 drive the speakers SP1 and SP2 respectively connected thereto by the input signals. On the other hand, in the transmitter 13, the microphone MIC 1 receives a signal such as a voice of the transmitter, and simultaneously receives a loudspeaker signal from the speakers SP 1 and SP 2 of the receiver 11. A reception signal such as a voice received by the microphone MIC 1 is amplified by an amplification circuit A4 provided in the transmission unit 13 and transmitted to the communication device 2 through the transmission system 18.

In the above, among the received signals such as the voices received by the microphone MIC1, only the voices of the sender remaining after the loudspeaker signals from the speakers SP1 and SP2 cancel each other are sent to the amplifier circuit A4 side. Sent. Therefore, not only the oscillation phenomenon but also the echo phenomenon does not occur between the transmitting and receiving units between the two communication devices 1 and 2. Communication equipment 2 However, since they perform the same function, they are more effective if they are incorporated in both communication devices 1 and 2.

In the above-described embodiment, an example has been described in which the distribution circuits 12 and 16 are configured by variable resistors. However, this is merely a preferred example, and the distribution circuits 12 and 16 are configured by members that exhibit similar effects such as a field-effect transistor. May be.

2 and 3 show another embodiment. In the embodiment shown in FIG. 1, distribution circuits 12 and 16 composed of variable resistors are used to adjust the magnitude of the reception signal voltage applied to the amplification circuits A 2 and A 3 for driving the two speakers. However, when the signal voltage set value by the variable resistors of the distribution circuits 12 and 16 fluctuates due to temperature fluctuations in the operating environment of the speakers SP 1 and SP 2 and the microphone MIC 1 and the characteristics of the components used, A control circuit for automatically resetting the fluctuation value to the set value may be provided, and FIGS. 2 and 3 show an example thereof.

That is, in this embodiment, instead of the distribution circuits 12 and 16 composed of variable resistors, distribution circuits 22 and 26 composed of field-effect transistors FET 1 and FET 2 that electronically control the distribution ratio are received. The amplifier circuit A1 of the unit 21 and the amplifier circuits A2 and A3; the amplifier circuit A5 of the receiver unit 25 and the amplifier circuits A6 and A7; The control circuits 28 and 29 for controlling 26 are installed on the output side of the microphone MIC 1 of the distribution circuit 22 and the transmission unit 23, and on the output side of the microphone MIC 2 of the distribution circuit 26 and the transmission unit 27. ing.

The control circuits 28 and 29 have the same configuration. As shown in detail in FIG. 3, one of the control circuits 28 is connected so as to be able to take in a part of the output signal from the microphone MIC 1 and converts a transmission signal into a pulsating flow 31. An integration circuit 32 connected to the rectifier circuit to obtain a DC signal voltage; and a comparison circuit connected to the integration circuit for comparing the DC signal voltage with a reference voltage. Circuit 33, and inverting amplifier circuits 34 and 35 that output control signals to the field effect transistors FET1 and FET2 so that the magnitude of the DC signal voltage is minimized in the comparison circuit. The reference voltage to be compared with the DC signal voltage in the comparison circuit 33 is constituted by a variable resistor 36 as shown, and a predetermined value is set after adjustment.

In this embodiment, a loudspeaker signal from a pair of speakers SP1 and SP2 and a speaker's voice and the like are received and amplified by a microphone MIC1 and transmitted, and at the same time, a part of the signal is rectified. The circuit 31 takes in the rectified current, pulsates it, converts it to DC by the integrating circuit 32, and obtains a DC signal voltage. The magnitude of the DC signal voltage is sufficiently canceled out when the loudspeaker signals from the speakers SP 1 and SP 2 are input to the microphone MIC 1, and is minimized. Therefore, when using the DC signal voltage to increase the amplification degree of the amplification circuit A2, the amplification degree of the amplification circuit A3 decreases, and the amplification degree of the amplification circuit A2 increases. When the resistance is reduced, the value of the adjustment variable resistor composed of the field effect transistors FET1 and FET2 is adjusted so that the amplification degree of the amplification circuit A3 increases in the opposite direction so that the DC The signal voltage should be minimized. The control voltages applied to the field-effect transistors FET1 and FET2 are adjusted by adjusting the amplification of the inverting amplifiers 34 and 35 so as to be the best value for the control. The comparison reference voltage is applied so as to output the minimum control signal.

In this embodiment, the same operation as that of the above embodiment can be expected. In addition, as described above, the electric field is changed by the temperature of the use environment of the speakers SP 1 and SP 2 and the microphone MIC 1 and the characteristic of the use component. Effect Even if the set value of the received signal voltage by the transistors FET1 and FET2 fluctuates, the fluctuation value is controlled by the control circuit 28. Is automatically reset to the set value.

FIG. 4 is a schematic diagram in which a pair of speakers SP 1 SP 2 and a microphone MIC 1 are hermetically incorporated in one earphone as a so-called “ear microphone”. In this drawing, the basic arrangement structure for performing the operation is shown, and any structure can be used as long as the loudspeakers SP 1 and SP 2 can collect sound from the microphone MIC 1 at the same time. There may be.

Note that the there is shown an example in which a speaker SP 1 ₃ SP 2 to the reception section 1 1, 1 5, 2 1, 2 5 in the embodiments may be provided Iyafo down Alternatively besides However, when the present invention is implemented, various design changes can be made within the scope described in the claims.

Claims

The scope of the claims

1. One communication device is composed of a microphone for transmitting a signal such as voice, a transmission unit including an amplification circuit, a speaker or earphone for receiving information, and a reception unit including an amplification circuit, and the other communication device. Is composed of a transmitting unit including a similar microphone and amplifying circuit, and a receiving unit including a speaker or earphone and an amplifying circuit, and these two communication devices are connected via a transmission system to enable two-way communication. That is

A plurality of the speakers or the earphones are installed in a receiver of one communication device, and a plurality of second amplifiers respectively connected to the speakers or the earphones are installed separately from the amplifier circuit. The magnitude of the received signal voltage that is amplified and supplied from the transmission system by the amplifier is not equal to the magnitude of the received signal voltage given to one amplifier circuit and the magnitude of the received signal voltage given to the other amplifier circuit. An echo prevention circuit characterized by a distribution circuit that is always unbalanced and distributes and sets the output voltage of the microphone to be the minimum.

2. The echo prevention circuit according to claim 1, wherein the distribution circuit is a variable resistor.

3. The distribution circuit is a field-effect transistor that electronically sets a distribution ratio between the magnitude of the received signal voltage applied to one amplifier circuit and the magnitude of the received signal voltage applied to the other amplifier circuit. 2. The echo prevention circuit according to claim 1, wherein

4. Use environment and usage of speakers or earphones and microphones A control circuit for automatically resetting the set value of the received signal voltage by the field effect transistor to the set value when the set value of the received signal voltage fluctuates due to a change in the characteristic of the component for use with temperature. An anti-echo circuit according to paragraph 3.

5. A control circuit is connected to be able to take in a part of the transmission signal from the microphone and converts the transmission signal into a pulsating flow; an integration circuit connected to the rectification circuit to obtain a DC signal voltage; A comparison circuit connected to the integration circuit for comparing the DC signal voltage with a reference voltage; and an inverting amplifier circuit for outputting a control signal to the field-effect transistor so that the magnitude of the DC signal voltage is minimized in the comparison circuit. 5. The echo prevention circuit according to claim 4, comprising:

6. One microphone is installed in the transmitting section of one of the communication devices, and this microphone simultaneously inputs a signal such as a loudspeaker signal from the loudspeaker or the earphone and a voice or the like emitted by the transmitter. 2. The echo prevention circuit according to claim 1, wherein the echo prevention circuit is arranged as follows.

7. In the receiver and transmitter of one communication device, a plurality of speakers or one microphone and one microphone are hermetically incorporated in one earphone to collect sound information transmitted from the ear. 7. The echo prevention circuit according to claim 6, wherein two-way communication for simultaneously loudspeaking is enabled.