SU651490A1 - Meter of level of distinct crosstalks in communication channels with pulse-code modulation - Google Patents

Description

The invention relates to communications and can be used to measure the level of intrinsic transient effects in channels of the tonal frequency and broadcasting of a communication system with pulse code modulation (PCM).

A known transient effects level meter in communication channels with pulse-code modulation contains a test signal generator on the transmitting side, connected to the input of the influence channel, and an auxiliary signal generator, and on the receiving side connected to the affected output. channel filter test signal selection indicator and a series-connected detector and constant-state filter 1.

However, in the known gauge, connecting the auxiliary signal generator to the input of the affected channel leads to a swing of the operating point of the quantizer, as a result of which the influence of changing the position of the operating point of the quantizer to the level of intermediate transient effects at its output decreases, i.e. unknown position of the quantizer operating point. Therefore, the uncertainty of the position of the working point causes the uncertainty of the measured value of the level of transient influences, and, consequently, the low measurement accuracy.

The aim of the invention is to improve the measurement accuracy.

For this, the level transient effects in the communication channels with pulse-code modulation, containing on the transmitting side a test signal generator connected to the input of the influence channel and an auxiliary signal generator, and on the receiving side connected to the output subject to influence. A channel of the test signal extraction filter, an indicator and a series-connected detector and a constant-component filter, are integrated on the transmitting side at the input of a low-frequency predistortion unit and a pulse repetition frequency divider whose output is connected to the input of the first pulse counter whose outputs are connected to the corresponding control the first scaled signal converter, the signal input of which is connected to the output of the low-frequency predistortion block, and They are series-connected reference voltage source, comparator, element I, the second input of which is connected to the output of the counting pulse generator, and the second pulse counter, the outputs of which are connected to the corresponding control inputs of the second scaler, and the setting input of the second pulse counter is connected to the first output of the control unit, the second output of which is connected to the third input of the element And, while on the transmitting side the output of the auxiliary signal generator is connected to the input the low-frequency predistortion block, the output of the first scaler of the signal is connected to the input of the affected channel, on the receiving side the output of the test signal selection filter is connected to the signal input of the second scaler of the signal whose output is connected to the input of the detector, the output of the filter is connected to the second input of the comparator, and the third output of the control unit is connected to the control input of the indicator, the signal inputs of which are connected to the corresponding, Exit second pulse counter.

FIG. 1 shows a structural electrical circuit of the proposed meter; FIG. 2 - voltage diagrams at characteristic points of the circuit.

The level meter of external transient effects in PCM communication channels contains, on the transmitting side, a test signal generator 1 connected to input 2 of the affecting karal, a generator of 3 auxiliary signals, combined at the input unit 4 low frequency predistortions and a frequency divider 5 pulse repetition, the first the pulse counter 6 and the first scaler 7 of the signal, the output of which is connected to the input 8 of the affected channel, on the receiving side is a filter connected to the output 9 of the affected channel. 10 test signal extraction, indicator 11, detector 12 and constant filter 13, reference voltage source 14, comparator 15, AND element 16, reference pulse generator 17, second pulse counter 18, second scale signal converter 19, control unit 20 .

The meter works as follows .-. .

On the transmitter side of the meter connected to the input 8 of the affected channel, an auxiliary signal is generated (Fig. 2a), the level of which varies discretely from zero to a level corresponding to, for example, the quantization step of the first segment.

With this form of auxiliary signal, changing its level is equivalent to shifting the operating point of the quantizer. From FIG. 26, it can be seen that almost all the signal samples of the internal transition effects from generator 1 (from input 2 of the influencing channel) fall into the “flat part of the auxiliary signal. From the output of the generator 3, the signal (Fig. 2c) is fed simultaneously to the inputs of frequency divider 5 and block 4 of low-frequency predistortion. Adjusted signal with. the output of block 4 (fig. 2d) is fed to the input of the first large-scale converter 7, which is a cascade-connected amplifiers, the transmission coefficients of which depend on the state of the corresponding bits of the first counter of 6 pulses. The state of the latter varies with the frequency of occurrence of pulses at its counting input, coming from the output of the frequency divider. 5 (Fig. 2d). . : - As can be seen from FIG. 2a, the level of the auxiliary signal at the input 8 of the affected channel increases discretely with the arrival of each successive pulse from the output of frequency divider 5 until the first counter 6 is filled, then drops to zero and then increases discretely again. In this case, the change in the level of the intrinsic transient effects at the output 9 of the affected channel is periodic (Fig. 2e).

At the receiving side of the meter, the measurement of the highest value of the sensitive transient effects is carried out. After the command "start at the second output of the control unit 20, the signal" installation (Fig. 2g) appears, which arrives at the installation input of the second counter 18. At the same time, the second counter 18 is completely filled. Then the second large-scale converter 19 has the largest possible transmission coefficient. After the termination of the signal "setting the first output of the control

20, a "measurement" signal (Fig. 2h) arrives at the third input of the And 16 element. When the signal is present, "measurement simultaneously with the resolution signal that arrives. from the output of the comparator 15 to the first input of the element AND 16, at the output. the last appears counting pulses. The second counter 18 is working on subtraction. The number written in it after the set signal decreases.

Claims (1)

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