JPH0324833A - Voice signal transmission system - Google Patents

Abstract

PURPOSE:To easily attain a privacy talking and to simplify the constitution of a system by transmitting the voice signal in a digital format. CONSTITUTION:In a transmission part, the voice signal is digitized by an A/D converter 2 and separated into frequency information and amplitude information. These pieces of information are arranged in a transmission frame in time division to form a binary data series. This data series is subjected to the enciphering processing and the error correction encoding processing and subjected to prescribed digital modulation by a modulator 11 to be transmitted. In a reception part, the data series is reproduced by digital demodulation, etc., of a demodulator 16, and frame synchronism is settled by detecting a synchronous word to reproduce frequency information and amplitude information, and the compounded audio signal is reproduced from both information. Thus, the privacy talking is easily attained and the constitution of a communication equipment is simplified without enlarging the scale.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an audio signal transmission system, and particularly to an audio signal transmission system suitable for mobile communications. (Prior Art) For example, the one shown in FIG. 3 is known as a voice signal transmission method conventionally employed in mobile communications.

In FIG. 3, the transmitting section (FIG. 3(a)) includes a perfect compressor 31 called a hard limiter, and an envelope line detector 32.
It basically includes an FM modulator 33, a multiplexer 34, and an SSB (single sideband) transmitter 35. t'::, The reception section (FIG. 3(b)) includes an SSB reception 1.41, a perfect compressor 42, a bandpass filter 43, and an FM demodulator 44.
and a multiplier 45. This audio signal transmission method is called the Rinconvex method.
The audio signal is separated into frequency component A and amplitude component B, and both are sent out separately (Figure 3 (C)). At this time, Hue
2008Z
By transmitting narrowband FM at a certain level, it is stabilized and the quality is improved. Regarding this Rinconvex system, please refer to the document "Tsukada: "Experiment and evaluation of Rinconvex system for VHF band communication" Radio Times. 5,
pp2-n <review 56)''. (Question H that the invention is intended to solve) By the way, in the voice signal transmission system used in mobile communication, there are three requirements: ■ narrow band, ■ good voice quality, and ■
In addition to requirements such as being resistant to fading, other conditions are also required, such as ■ being able to communicate confidentially easily, and ■ being able to use a nonlinear amplifier to save power. The conventional audio signal transmission system described above is essentially an analog transmission system, and although it satisfies the conditions (1) and (2), it does not satisfy the conditions (2) and (3). Therefore, we are considering going digital, but there is a problem of ε, which increases the scale of the equipment and makes it unsuitable for L2 mobile communications. The present invention was developed in view of the above circumstances, and its purpose is to enable simple digital processing, that is, to easily communicate confidential information without increasing the scale of the device, and to save power. The aim is to provide an audio signal transmission system suitable for mobile communications. (Means for Solving the Problems) In order to achieve the above object, the audio signal transmission method of the present invention has the following structure. That is, in the audio signal transmission method of the present invention, the transmitter a pre-processing section that performs compression processing etc. on the audio signal; a first A/D that samples the output of this pre-processing section at a predetermined sampling frequency and outputs an n-bit signal for each sample;
a converter; a polarity discriminator that receives the output of the first A/D converter and extracts and outputs a polarity bit; the first A/D converter;
an amplitude detector that performs absolute value operation on the output of every N samples of the /D converter and outputs an m (m≦n) bit signal;
a frame synthesis circuit that time-divisionally arranges the predetermined number of polarity bits and the m-bit signal in a transmission frame that repeats at a constant period with a synchronization word consisting of a fixed bit pattern at the beginning to form a binary data sequence; a transmitting baseband F signal processing circuit that performs error correction encoding and encryption processing on the output of the frame synthesis circuit; a modulation 22 that digitally modulates a predetermined carrier wave with the output of the transmitting paceband signal processing circuit; ! a first demodulator in which the receiving section performs quasi-synchronous demodulation processing on the received intermediate frequency signal and outputs a received baseband signal; a second demodulator which digitizes the received baseband signal;
a D converter; a second demodulator that performs digital demodulation processing on the output of the second A/D converter;
a receiving side baseband signal jamming circuit that performs error correction decoding processing and encryption decoding processing on the output of the demodulator; a signal separation circuit that establishes and separates and outputs the polarity bit and the m-bit signal; a multiplier that multiplies the m-bit signal separated and outputted by the signal separation circuit by the polarity bit; and the output of the multiplier. A D/AyR converter that converts the D/AyR into analog:
The system is characterized by comprising: a post-processing unit that performs decompression processing, etc. on the output of the A converter and reproduces and outputs the audio signal; and; (Function) Next, the function of the audio signal transmission system of the present invention, which is explained above, will be explained. The transmitter first digitizes the audio signal and separates it into frequency information and amplitude information. That is, the frequency information is formed by extracting the polarity bit, and is also done in the form of amplitude information or by extracting an m-bit signal from the output of every N samples of the first A/D converter. That is, they focused on the characteristics of the audio signal and attempted to encode the audio signal using extremely simple digital processing. Next, these frequency information and amplitude information are time-divisionally arranged within the transmission frame to form a binary data sequence. Then, the second data series is subjected to encryption processing and error correction encoding processing, and is then subjected to predetermined digital modulation and transmitted.

Then, the receiving section reproduces the data sequence by digital demodulation or the like. Frame synchronization is established by synchronization word detection, the frequency information and vibration information are reproduced, and the original audio signal is reproduced from these two signals. Thus, according to the audio signal transmission system of the present invention, audio signals can be transmitted in digital format, making it possible to easily communicate secret conversations, and using a nonlinear amplifier as a transmission amplifier to improve power efficiency. can. Additionally, audio signals can be encoded using simple digital processing.
Communication equipment can be configured into Wj elements without increasing its scale. Furthermore, since it uses error correction coding technology, it is naturally resistant to fading. In other words, it is possible to provide an audio signal transmission system that is truly suitable for mobile communications. (Example) Examples of the present invention will be described below with reference to the attached drawings. Figure 1 shows an audio signal transmission system according to an embodiment of the present invention. The method of this embodiment uses the QPSK modulation method. First, in the transmitting section (Fig. 1(a)), the audio signal is input to the preprocessing section 1.The preprocessing section 1 is equipped with a low-pass filter and a compressor, and the input audio signal and its amplitude are A sample of a predetermined frequency (IN.j is 8 KHz) supplied from the timing signal generator 6, which is subjected to compression processing according to the level and output to the A/D converter 2. Signal C,: Therefore, the output of preprocessing section 1 is sampled L
2 For each sample, a predetermined sample Il/value of n bits (for example, n-10 bits 1) is determined by the polarity discriminator 3 and the vibration detector 4.
Output to. The polarity discriminator 3 is A. ．． , z' The polarity bit 9 of the output sample value of the D converter 2, that is, the upper bit of the quantity! -(M
SB〉 and show it directly. Output to I converter 5. This polarity bit indicates frequency information. The serial-to-parallel converter 5 receives a predetermined frequency, for example 8K}!, supplied from the timing signal generator 6. According to the timing signal of the polarity discriminator 3, the output bit 1 of the polarity discriminator 3 is divided into two series of signals (
P. Convert to Q). For example, if the odd output bit is p
The even-numbered output bits are distributed to the C word/sign sequence and the Q signal sequence, respectively. The output data rate of the polarity discriminator 3 is 8 K bps (bit per second).
d), the data rate of this converted signal system (P, Q) is 4 Kbps. This is output to the frame synthesis circuit 7. On the other hand, the amplitude detector 4 operates the absolute value of the output sample value of the A/D converter 2 every N samples (every 80 samples), that is, if the polarity bit is "1", it is "0' m (m≦n> bits (for example, the upper 8 bits) are extracted from the sample value thus obtained, and are converted into a bit series and output to the frame synthesis circuit 7. In other words, the amplitude information is frequency 1
This means that the data was sampled at 00Hz5, so the data rate is 800 bps. In the frame synthesis circuit 7, according to the timing signal supplied from the timing signal generator 6, a P signal system transmission frame (FIG. 2(a)) and a Q signal system transmission frame (second
Figure (b)) and the baseband signal processing times F! Output to Il8. That is, one frame consists of a synchronization word (UWP, UWQ) at the beginning and a data section following this, and is formed by inserting a predetermined number of amplitude information A and frequency information F in this order into the data section. ．． Specifically, since 8-bit data is supplied in series from the amplitude detector 4, this is divided into 4-bit units and one is assigned to the P signal system and the other to the Q signal system.
At this time, error correction encoding processing in the baseband signal processing circuit 8 at the subsequent stage is performed on these four bits, and α redundant bits are added. Therefore, in this frame synthesis circuit 7, the amplitude information A is arranged as a signal of (4+α) bits. The frequency information F that follows this is determined by a predetermined number of bits in the signal system corresponding to the polarity bit string supplied in advance from the serial-to-parallel converter 5 in two series. Further, the synchronization word UWP and the synchronization word UWQ consist of fixed bit patterns of the same bit length (for example, 40 bits), and the bit patterns are made to be different from each other in order to identify the signal system on the receiving side. The length of this frame is, for example, 15 frames per second, 400 bits of amplitude information, and 4000 bits of frequency information.
If it is specified that it can be transmitted in bits, the synchronization word will be transmitted in 600 bits. Since this is transmitted in two series, the data rate is 5000 sps (
sample per second). The bandwidth is not that wide. The baseband signal processing circuit 8 performs encryption processing and error correction encoding processing on each of the two data sequences output from the frame synthesis circuit 7 in accordance with the timing signal from the timing signal generator 6.

The two series outputs of this baseband signal processing circuit 8 are output from the corresponding waveform shaping filters (9P, 9Q) and the D/A converter (
input to the QAM modulator 11 via IOP, IOQ>,
The transmission carrier wave from the transmission carrier generator 12 is output as a transmission signal which is orthogonally modulated. Next, in the receiving section (FIG. 1(b)), the received IF (intermediate frequency band) signal is input to the QAM demodulator 13, where the received carrier wave from the received carrier wave generator 14 is used to generate two series of signals. is demodulated quasi-synchronously. These two series of quasi-synchronous demodulated signals are identified by corresponding A/D converters (15P, 15Q) and reproduced into baseband signals by a digital demodulator 16.

Note that the timing signal reproducing circuit 17 reproduces a timing signal based on the reproduced baseband signal output of the digital demodulator 16, and transmits the timing signal to the A/D converter (15P, 15Q).
, baseband signal processing circuit 18 and signal separation circuit 19
They supply each to The baseband signal processing circuit 18 performs error correction decoding processing and encryption decoding processing on the two series of reproduced baseband signals, respectively, and outputs them to the signal separation circuit 19. In the signal separation circuit 19, synchronization words (UWP,
UWQ) is detected to establish frame synchronization, and frequency information is extracted from each of the two series of frames.
The signals are directly output to the parallel-to-serial converter 20 as two series of signals. On the other hand, amplitude information is extracted from two sequences of frames, combined into one signal sequence, and output to the amplitude regenerator 21. The parallel-to-serial converter 20 performs an operation opposite to that of the serial-to-parallel converter 5 on the transmitting side, and supplies it to one input of the multiplier 22 as the original bit series polarity bit string. On the other hand, the amplitude regenerator 2l
converts the input bit-serial amplitude information into bit-parallel information and supplies it to the other input of the multiplier 22. As a result, the multiplier 22 outputs a signal with a predetermined bit pattern in which the polarity bit is modulated with amplitude information. This is D/
The signal is converted into an analog signal by the A converter 23, subjected to low-pass filtering and expansion processing by the post-processing section 24, and output as a reproduced audio signal. Although the embodiment described above is an application example of the QAM method, it is clear that other digital modulation methods such as the PSK (phase keying) method can also be realized using the same concept. (Effects of the Invention) As explained above, according to the audio signal transmission system of the present invention, audio signals can be transmitted in digital format, so confidential conversations can be easily carried out. Efficiency can be improved. Also. ,
Since audio signal encoding can be achieved through simple digital processing, communication equipment can be simply configured without increasing its scale. Furthermore, since it uses error correction coding technology, it is naturally resistant to fading. In other words, it has the effect of providing an audio signal transmission system that is truly suitable for mobile communications.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the structure of an audio signal transmission system according to an embodiment of the present invention, FIG. 2 is a block diagram of a transmission frame, and FIG. 3 is a block diagram of a conventional Rinconvex system. 1...Preprocessing section, 2...A/D converter, 3...Polarity discriminator, 4...Amplitude detector, 5... ...Series-to-parallel converter, 6...
...Timing signal generator, 7...Frame synthesis circuit, 8...Baseband signal processing circuit, 9P, 9Q...Waveform shaping filter, IO
P, IOQ...D/A converter, 11...
...QAM modulator, 12...... Transmission carrier generator, l3... QAM demodulator, 14...
... Reception carrier wave generator, 15P, 15Q.・・・・・・
・A/D converter, 16...digital demodulator,
17...timing signal regeneration circuit, 18
...Baseband signal processing circuit, 19...
... Signal separation circuit, 20 ... Parallel-serial converter, 21 ... Amplitude regenerator, 22 ...
Multiplier, 23...D/A converter, 24...
...Post-processing section.

Claims (1)

[Claims] The transmitter includes a preprocessor that performs compression processing on the input audio signal; and a first A/D that samples the output of the preprocessor at a predetermined sampling frequency and outputs an n-bit signal for each sample. a converter; a polarity discriminator that receives the output of the first A/D converter and extracts and outputs a polarity bit; and performs absolute value operation on the output of every N samples of the first A/D converter; an amplitude detector that outputs a signal of (m≦n) bits; a predetermined number of polarity bits and the m-bit signal are time-divided within a transmission frame that repeats at a constant period with a synchronization word consisting of a fixed bit pattern at the beginning; a frame synthesis circuit for arranging and forming a binary format data sequence; a transmitting side baseband signal processing circuit for performing error correction encoding processing and encryption processing on the output of this frame synthesizing circuit; and this transmitting side baseband signal processing circuit. a modulator that digitally modulates a predetermined carrier wave with the output of the circuit; a first demodulator in which the receiving section performs quasi-synchronous demodulation processing on the received intermediate frequency signal and outputs a received baseband signal; a second A/D converter for digitizing the band signal;
a second demodulator that performs digital demodulation processing on the output of the second A/D converter; a receiving side baseband signal that performs error correction decoding processing and encryption decoding processing on the output of the second demodulator; a processing circuit; a signal separation circuit that receives the output of the receiving side baseband signal processing circuit, establishes frame synchronization by detecting the synchronization word, and separates and outputs the polarity bit and the m-bit signal; the signal separation circuit; A multiplier that multiplies the m-bit signal that the circuit separates and outputs by the polarity bit; D that converts the output of this multiplier into an analog
1. An audio signal transmission system comprising: a /A converter; and a post-processing unit that performs decompression processing, etc. on the output of the D/A converter and reproduces and outputs the audio signal.