JPS59200543A - Analog voice processor - Google Patents

Abstract

PURPOSE:To perform radio analog transmission with good voice quality by converting a voice signal to frequencies in a frequency range which is much higher than its original frequency band, and performing one-bit quantization before transmission. CONSTITUTION:A voice signal from a terminal 1 is limited to frequency bands f1-f2 by a BPF2 while a frequency band which exerts no influence upon the voice quality are excluded, and the output of a sine wave oscillator 3 is adjusted to lower than the mean level of the voice signal and inputted to a synthesizer 4 to generate a composite signal. The output of a local oscillator 5 of high frequency f0 is modulated by a balanced modulator 6 with the composite signal and frequency-converted, and a BPF7 extracts (f0+f1)-(f0+f2), which are supplied to a one-bit quantizer 8 for one-bit quantization; and a BPF8 removes higher harmonics generated at the quantizer 8, and a one-bit quantized signal is outputted from an encoder output terminal 10. A decoder multiplies a signal from a terminal 11 by the output of a local oscillator 12 through a mixer 13 and the reproduced voice signal obtained by passing the output of the mixer through an LPF14 and a BPF15 is outputted from a terminal 16.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention encodes an audio input signal using an encoder and transmits the encoded signal.
The present invention relates to an analog audio processing device in which a decoder decodes and extracts the audio on the receiving side.

In conventional devices of this type, a zero-crossing wave circuit was used on the encoder side to quantize the audio input signal by one bit in the audio frequency band. The disadvantage was that there was a lot of noise, and the desired telephone quality could not be obtained.

The present invention has been made in order to eliminate the drawbacks of the prior art as described above, and therefore, an object of the present invention is to provide an analog voice processing method capable of achieving a predetermined telephone quality with less noise in the reproduced sound. The goal is to provide equipment.

The key point of the configuration of the present invention is that 1-bit quantization is performed after converting the frequency of the audio signal to a sufficiently high frequency range compared to the frequency band of the audio signal, thereby achieving wireless transmission with good audio quality. This enabled audio processing suitable for realizing analog transmission.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, 1 is an audio signal input terminal, 2 is a band pass filter (BPF), 3 is a sine wave oscillator, 4 is a synthesizer, and 5
is a local oscillator, 6 is a balanced modulator, 7 is a band pass filter (BPF), 8 is a limiting circuit, 9 is a band pass filter (BPF), 10 is an encoder output terminal, 11 is a decoder input terminal, 12 is a local oscillator, 13 is a mixer,
14 is a low pass filter (T, PF), 15 is a band pass filter (BPF), and 16 is a reproduced sound output terminal.

The operation of this embodiment will be explained in detail below. The audio signal input to the audio signal input terminal 1 is filtered by the bandpass filter 2 from f 1 to f 2 (for example, from f 1 to 300 t'lz
.

f 2 = 3.4 KHz)).
00112) is inserted by the combiner 4 to form a composite signal.

The sine wave level in the composite signal is adjusted to be lower than the average level of the audio signal (for example, a level difference of 20 dB).

The oscillation frequency of the dilocal oscillator 5 is 6° (for example, fo-45
The balanced modulator 6 modulates the output of the 5IGIz) using the synthesized signal as a modulation input, and the bandpass filter 7 removes unnecessary waves, thereby converting the frequency band (fo-4
-ft )~(fo+f2) or (fo-fl)~(
A synthesized signal frequency-converted to fo f2) is obtained (hereinafter, the case of (fo+f1) to (fo+f2) will be explained).

The frequency-converted composite signal is 1-bit quantized by a limiter circuit 8 serving as a 1-bit quantum device, and harmonics generated by the 1-pit quantization are removed by a band spring filter 9, resulting in a frequency band of (fO+fl) to (fo+f2). A 1-bit quantized signal of 1 is output to the encoder output terminal 10. Note that the purpose of inserting the above-mentioned sine wave signal is to suppress noise when the voice is unattended.

Further, a 1-bit quantum device can be realized by, for example, a limit circuit.

Next, the signal input to the decoder input terminal 11 is multiplied by the output of the local oscillator 12 (the oscillation frequency is equal to that of the local oscillator 5) in the mixer 13, and the harmonics generated in the mixer 13 are transmitted to the low-pass filter 14. is removed, a reproduced audio signal is obtained by the bandpass filter 15 (pass band is equal to that of the bandpass filter 2), and outputted from the reproduced sound output terminal 16.

FIG. 2 is a block diagram showing another embodiment of the invention.

In the figure, 17 is a band pass filter, 18 is a detector, 19 is an AGC circuit, and other numbers are the same numbers as in the embodiment of FIG. 1.

FIG. 3 is a graph showing the relationship between the level ratio of the audio signal to the sine wave signal at the output of the synthesizer 4 in FIG. 2 and the relative level of the sine wave signal at the output of the bandpass filter 7 in FIG.

From FIG. 3, it can be understood that, assuming the level of the sine wave signal is constant, the higher the level of the audio signal, the lower the reproduction output (relative value) of the sine wave signal that is the output of the bandpass filter 7. Will.

In other words, a change in the output level of the bandpass filter 7 can be said to represent a change in the level of the audio signal.

From the output of Lohas filter 4 to bandpass filter 1
5 to obtain an audio signal, and a band pass filter 17 (for example, passband 2,200±50 ITz) to obtain a reproduced signal of the previously inserted sine wave. Since the level of this reproduced signal is inversely proportional to the level of the audio signal, this reproduced signal is detected by the detector 18, and the detected output is used to transmit the signal to the AG.
The gain of the C circuit 19 is controlled to more faithfully reproduce the rough audio signal amplitude component obtained from the bandpass filter 5, and high quality reproduced sound is output from the reproduced sound output terminal 161C.

As explained above, when using the audio processing device according to the present invention, the audio input signal is frequency-converted to a frequency band higher than the audio frequency band and then 1-bit quantized. Compared to conventional devices that use circuits to perform 1-bit quantization, it is possible to obtain reproduced sound with better quality.

Furthermore, since the processed audio waveform has a constant amplitude, it can be suitably used for analog transmission of audio over a transmission line where large level fluctuations due to fading occur, such as in mobile radio.

[Brief explanation of drawings]

FIGS. 1 and 2 are block diagrams showing one embodiment of the present invention, and FIG. 3 is a graph showing the relationship between the sine wave signal output and the sine wave signal to audio signal level ratio. Description of symbols 1...Audio signal input terminal, 2...Band pass filter, 3...Sine wave oscillator, 4...
...Synthesizer. 5...Local oscillator, 6...Balanced modulator, 7...Band pass filter, 8...
...1 bit it child i. 9...Band pass filter, 10...
Encoder output terminal, 11... Decoder input terminal, 1
2...Local source mW, 13...Mixer, 14...Low pass filter, 15...
... Band pass filter, 16 ... Playback sound output terminal, 17 ... Band pass filter. 18...Detector, 19...AGC circuit agent Patent attorney Akio Namiki Agent Patent attorney Kiyoshi Matsuzaki (ffi4#at) Cl-Hirati4'&i4'l'='
tr? Procedural amendment June 29, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 1983, No. 587741032, Title of the invention: Analog audio processing device 3, Person making the amendment Relationship with the case: Patent applicant Address: 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Name (
422) Nippon Telegraph and Telephone Public Corporation Representative Tsune Shinfuji 4, Agent address 3rd floor 6, Otsuka Building, 5-4 Toranomon-chome, Minato-ku, Tokyo, Figure 5 of the drawings subject to amendment, Figures 1 and 2, 7; The details of the amendment are as shown in the attached sheet.

Claims (1)

[Scope of Claims] 1) In an analog audio processing device in which an audio input signal is encoded and transmitted by an encoder and then decoded and extracted by a decoder, the encoder is configured to determine the audio quality of the audio input signal. a first circuit that inserts a sine wave in a frequency band that does not influence a third circuit that quantizes the frequency-converted output signal from the second circuit; and a bandpass filter that removes harmonics generated by the quantization from the quantized output signal of the third circuit. The decoder has a fourth circuit that uses the filter output as an encoder output, and the decoder has a fifth circuit that receives the encoder output and converts the frequency band into a voice band frequency band. , a sixth circuit as an audio band filter for obtaining reproduced sound from the frequency conversion output. 2) In an analog audio processing device in which an audio input signal is encoded and transmitted by an encoder and then decoded and extracted by a decoder, the encoder uses a frequency that does not affect the audio quality of the audio input signal. a first circuit that inserts a sine wave in a frequency band; a second circuit that converts the frequency of the audio input signal into which the sine wave has been inserted into a frequency range that is sufficiently higher than the frequency band; a third circuit for 1-bit quantization of the output signal from the circuit; and a fourth circuit as a bandpass filter for removing harmonics generated by the quantization from the quantized output signal of the third circuit. The decoder includes a fifth circuit that receives the encoder output and converts the frequency band into a voice band frequency band; a sixth circuit as an audio band filter for obtaining reproduced sound; a seventh circuit as a band filter for extracting the reproduced output of the sine wave signal from the output of the fifth circuit; and the extracted sine wave signal. and a ninth circuit that uses the detected output to control the amplification gain of the reproduced sound signal that is the output of the sixth circuit to improve the quality of the reproduced sound. An analog audio processing device characterized by: