SU421139A1 - MODULATOR OF THE TELEPHONE CHANNEL WITH PULSE-CODE MODULATION - Google Patents

Description

one

The invention relates to the technique of converting analog signals to discrete ones and can be used in low-channel radio relay stations with temporary compaction of telephone channels and pulse-code modulation (PCM).

Known communication systems with PCM, built on the principle of CI counting.

The use of the CI counting method in the construction of the PCM equipment of a radio relay station eliminates the technological difficulties that occur in bitstream coders (the need to select elements, the use of highly stable and high-precision etadone-resistor matrices, etc.).

When counting the PCM siphla, the quantization noise in the telephone channel is entirely determined by the size of the conversion of the VL to binary code. However, in practical implementation, an increase in the frequency of CIs is limited by the speed of the first stages of the counter.

To increase the accuracy of conversion (coding bit) without increasing the frequency of the CI following frequency, the method of delayed coincidence (MZS) is used. The essence of the MZS is that the moment of termination of the encoded IW is updated with respect to the additional time stamps formed from

the original CI sequence with the help of a delay line (LZ) with taps, which includes identical sections with time „„ “

the delay of each section is equal to / GT1

(where Tk is the period of the trace} and initial CI). At the same time, in the code combination displaying the IW value, the bit values from i + l to the leading / -YY are determined as usual by the number

The CIs received from the quantizing impulse generator (SCI) to the counter during the IW, and the low-order bits from first to / -th are determined by the display device (decryption) by signals from the outputs of the gate

circuits connected to the LZ taps. The number of LZ sections, equal to n, is related to the number of additional least significant bits i formed by the MZS, the ratio In the known device, the pulses from each

removal of LZ come through high-frequency valve circuits to the corresponding counting triggers during the entire encoded IW.

The purpose of the invention is to reduce the noise in the channel.

This is achieved by connecting to the control inputs of the inhibit circuits, except the last, the OR circuits, the first inputs of which are connected to the mentioned output of the converter, the analogue is time, and the other inputs are connected to the corresponding branches of the partitioned delay line.

The block diagram of the proposed modulator is presented in FIG. 1, where 1-converter "analog - time; 2 - generator of quantizing pulses; 3 - older bit counter; 4 - prohibition scheme; 5 - sectioned delay line; 6-8 - prohibition schemes; 9- II - schemes “OR, 12 - a decoder; 13 - parallel code to serial converter.

FIG. 2, time diagrams are given that explain the operation of the proposed modulator by the example of the formation of two lower-order bits by the method of delayed matches, where a is the time interval at the output of the analog-to-time converter 1; b - pulses at the output of the generator of quantizing pulses 2; в, г, д, - impulses on branches of the sectioned delay line 5; e, g - two low-order bits at the output of the decoder 12; h - the first bit of the high-order counter 3; and - quantization error diagram.

The telephone channel modulator with pulse code modulation contains an analog-time 1 converter, which is connected to the high-order counter 3 by the inhibitor circuit 4 and the partitioned delay line 5, whose outputs are connected with the inhibit circuits 6-8 and circuits of the type "OR 9-11, other inputs of which are combined and connected to the output of the converter" analog - time 1. The outputs of the circuits OR 9-11 are connected to the control inputs of the decoder 12. The outputs of the high-order counter 3 and the decoder 12 are connected to zovatelyu 13 parallel to serial.

Works proposed modulator as follows.

The analog-to-time converter 1 converts a low-frequency input signal into width-modulated time intervals (TR), (see Fig. 2, a), the duration of which is proportional to the instantaneous values of the input signal in clock flows tested. The pulses (a) from the output of the converter 1 act on the generator of the quantizing pulses 2, made according to the shock excitation scheme. The bundle of quantizing pulses (b) is generated, firstly, to the input of the high-order counter 3, which converts the number-pulse code into a parallel binary code, secondly, to the input of the prohibition circuit 4 and, thirdly, to the input of the partitioned delay lines 5, from whose outlets the pulse sequences (c, d, d with the corresponding delays arrive at the inputs of the inhibitor circuits 6-8. Transducer

The analogue - time 1 acts through the OR 9-11 circuits on the control 1, not the inputs of the circuits 4, 6, 7, 8, and keep them in a locked state during the entire coded IW. 5 In addition, the control inputs of the inhibit circuits 4, 6, 7 through the circuits OR 9-11 receive pulses from the taps of the delay line 5. If, for example, as shown in fig. 2, in the moment of termination of IW at the outputs of the first two (e) and

10 of the second (d) section of the LZ, there were simultaneously pulses, then the prohibition scheme 6, connected to the output of the previous (first) section, is kept closed during the action of the pulse (g) at the output of the subsequent (second) section of the LZ. As a result, after termination of IW at the output of the prohibition scheme 6, the pulse will be absent. This is equivalent to the fact that pulses with a duration equal to the delay value of one section arrive at the inputs of the inhibit circuits.

Thus, the proposed device allows to work with pulses of a sufficiently long duration (), at the output of the quantizing pulse generator 2. Moreover,

5 the choice of the duration of these pulses is not critical.

The pulses from the outputs of the prohibition schemes 4, 6, 7, 8, are fed to the decoder 12, which contains low-frequency triggers with separate

0 inputs and a diode array that generates low-order values for trigger readings. The parallel binary code from the outputs of the high-order counter 3 and the decoder 12 is fed to the parallel-to-serial code converter 13 and further to the communication channel.

Subject invention

0 L1 module of telephony channel with pulse-code modulation, containing analog-time converter, the output of which is connected through a generator of quantizing pulses to the input of a sectioned delay line with ha taps and to the input of a high-order counter connected to a parallel code converter to a serial one, to inputs which connected n taps of a partitioned delay line through a barring circuit, the other inputs of which are connected to the output of the converter "analogue - time, characterized in that, in order to reduce no noise in the channel, to the control inputs of the prohibition schemes, except the last one, are connected

“OR” circuits, for the first time the inputs of which are connected to the output of the converter “analog-time, and the other inputs are connected to the corresponding outlets of the partitioned delay line.

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