JPH09130282A - Method for reducing noise of digital radio communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise sound in the silence by detecting the silent time and lowering the gain of a receiving speech amplifier. SOLUTION: In a system for reducing the noise of a digital radio communication equipment for performing radio communication by a TDMA(time division multiplexing access) system, the receiving speech amplifier 4 capable of gain control for amplifying received voice signals is provided, and in transmitting the output signals of a silence detecting function 3-2b to an opposite station, the output signals of the silence detecting function of the received opposite station are received through an antenna 1 and a radio part 2 in a control part 8, the gain of the receiving speech amplifier 4 is controlled and the noise sound in the silence is reduced by suppressing the gain of the receiving speech amplifier 4 low only the silence time in the communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reducing voice noise in a digital wireless communication device for voice communication using digital wireless transmission according to a TDMA (Time Division Multiple Access) system.

[0002]

2. Description of the Related Art FIG. 2 shows a configuration example of a digital communication device adopting a conventional noise reduction method. As shown in the figure, the digital communication device is an ordinary PHS telephone, for example, an antenna 21, a radio section 22, a voice codec section 23, and an amplifier 2.
4, a receiver 25, an amplifier 26, a transmitter 27, and a control unit (microprocessor) 28. Voice
The deck unit 23 includes a decoder 23-1, a VOX function unit 23-
2 and encoder 23-3, and VOX (voice
The function section 23-2 includes a background noise generating function 23-2a and a silence detecting function 23-2b.

A data signal received by the antenna 21 is amplified and detected by a radio section 22, and the data signal is decoded by a decoder 23-1 of a voice codec section 23 to become a voice electric signal, which is amplified by an amplifier 24. Then, it is output as voice from the handset 25. The output signal (voice electric signal) of the transmitter 27 is amplified by the amplifier 26, coded by the encoder 23-3 of the voice codec unit 23, and input to the radio unit 22 as a data signal. . The radio section 22 modulates and amplifies the data signal and transmits it from the antenna 21.

FIG. 3 is a diagram showing a slot configuration of a PHS telephone and a transmission signal. FIG. 3A shows a PHS slot configuration and FIG. 3B shows a transmission signal. In the figure, T is a transmission slot, R is a reception slot,
I is an idle slot. The PHS access system is a TDMA system in which transmission and reception are alternately performed, and the transmission and reception are time-divided into 4 multiplex. Therefore, the transmission radio wave is intermittently output in the slot having a length of 5/8 ms every 5 ms ((b) in the same figure).

This transmission radio wave output intermittently is induced from the radio section 22 into the voice circuit and becomes noise, and the amplifier 24
May be amplified by and output from the handset 25 as a noise sound. This noise has a frequency of 200 Hz, and 200 Hz and its harmonics are mixed in the call voice.

The above-mentioned noise sound is not a level that normally disturbs a call, but is a level that can be slightly heard in a silent state, but various noises such as those of analog radios are mixed. Because it does not come, it becomes annoying when there is no voice input during a call. Conventionally, in order to eliminate this noise, measures such as optimizing component arrangement, adding shields, and adding capacitors for noise paths have been taken. In addition. In the operation of the VOX function unit 23-2, normally, on the transmission side, the silence detection function 23-2b detects the presence / absence of the transmitted voice and outputs it to the control unit 28. On the receiving side, the background noise generation function 23-2a causes the background noise to be generated when there is no sound.

[0007]

However, in the conventional noise reduction method, it is necessary to repeat trial-and-error of trial production-evaluation-revision every time the printed circuit board, component layout and shape are changed, and re-evaluate each time. There was a problem that the period was long and the cost was high. In addition, the VOX function unit 23-
The original operation of 2 cannot remove the noise in question. The reason is that the noise at issue here occurs because the transmission carrier is detected by the audio amplifier, and therefore occurs regardless of the audio output signal from the audio codec unit 23.

The present invention has been made in view of the above-mentioned problems, and in order to eliminate the above-mentioned problems, a digital radio communication device for detecting a silent time and reducing a gain of a receiving amplifier to reduce a noise sound at the silent time. It is an object of the present invention to provide a noise reduction method of.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a noise reduction method for a digital communication device which performs wireless communication by the TDMA method, as shown in FIG. 1, a gain for amplifying a received voice signal. The output signal of the controllable reception amplifier 4 and the silence detection function 3-2b is transmitted to the partner station, and the silence detection function 3 of the received partner station is received.
-2b output signal causes the controller 8 to control the gain adjuster 4-2.
To control the gain of the reception amplifier 4. This is characterized in that the noise of the silence is reduced by suppressing the gain of the reception amplifier 4 to a low level only during the silence during the call.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a digital communication device that employs the noise reduction method of the present invention. As shown in the figure, the digital communication device to which the noise reduction method of the present invention is applied includes an antenna 1, a radio unit 2, a voice codec unit 3, a reception amplifier 4, a reception unit 5, an amplifier 6, a transmitter 7, and a control unit ( Microprocessor) 8. The audio codec unit 3 includes a decoder 3-1 and a VOX function unit 3-2.
And an encoder 3-3, and a VOX function unit 3-
2 is a background noise generation function 3-2a and a silence detection function 3-2b
Is provided. Further, the reception amplifier 4 includes an amplifier 4-1 and a gain adjuster 4-2.

In the digital communication device having the above structure, the data signal received by the antenna 1 is amplified and detected by the radio section 2, and the data signal is decoded by the decoder 3-of the voice codec section 3.
1 is decoded into a voice electric signal, which is output as voice from the receiver 5 through the amplifier 4-1 of the receiver amplifier 4 and the gain adjuster 4-2.

The output signal (voice electric signal) of the transmitter 7 is amplified by the amplifier 6, and the encoder 3 of the voice codec section 3 is amplified.
Is coded at -3 and is input to the radio unit 2 as a data signal. The radio unit 2 modulates and amplifies the data signal and transmits it from the antenna 1.

In the present invention, the VOX function section 3-2 of the voice codec section 3 detects a silent voice to detect the presence or absence of a call voice.
-2b is provided, the output signal thereof is transferred to the control unit (microprocessor) 8, and is transmitted from the control unit 8 to the other party via the wireless unit 2 and the antenna 1. On the other hand, the output signal of the silence detecting function 3-2b of the other party is received via the antenna 1 and the wireless unit 2 and transferred to the control unit 8, and the control unit 8 causes the microprocessor to receive the received signal (VOX input signal). The gain adjuster 4-2 of No. 4 is controlled to control the gain.

As described above, in the present embodiment, the voice detector (detection circuit) 3-1 for detecting the presence or absence of the call voice is provided, and the gain of the reception amplifier 4 is kept low when there is no sound.
The noise sound output from the handset 5 can be suppressed to a low level.

[0015]

As described above, according to the present invention, the following excellent effects can be obtained. (1) Since the gain of the receiver amplifier is controlled to be low only when there is no sound, there is a positive effect against noise when there is no sound even when noise is generated due to changes in the printed circuit board, component layout and shape. The development period can be greatly reduced without repeating trial and error for noise elimination.

(2) Further, since the noise is noise peculiar to digital radio and the VOX control signal can be diverted, the noise can be reduced only by controlling the gain of the reception amplifier of the communication terminal to be low when there is no sound. Therefore, it is suitable for a digital mobile communication terminal, and a large effect can be obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a noise reduction method for a digital communication device of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a conventional noise reduction method for a digital communication device.

FIG. 3 is a diagram showing a slot configuration and a transmission signal of a PHS telephone, (a) showing a PHS slot configuration,
(B) is a figure which shows a transmission signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 antenna 2 radio part 3 voice codec part 3-1 decoder 3-2 VOX function part 3-3 encoder 4 receiver amplifier 4-1 amplifier 4-2 gain adjuster 5 receiver 6 amplifier 7 transmitter 8 control part

Claims (1)

[Claims] 1. A noise reduction method for a digital wireless communication device that performs wireless communication according to the TDMA method, wherein the digital wireless communication device is provided with a reception amplifier capable of gain control for amplifying a received voice signal, When the output signal is transmitted to the partner station, the gain of the receiver amplifier is controlled by the received output signal of the silence detector of the partner station, and the gain of the receiver amplifier is suppressed to a low level only when there is no sound during a call. A noise reduction method for a digital wireless communication device, which is characterized by reducing noise noise.