SU1223380A1 - Device for measuring non-linear distortions in communication channel - Google Patents

Abstract

The invention can be used to measure the attenuation of the nonlinearity of the 3rd harmonic of the path elements - unattended and serviced amplifying points (LUP and PMO) - and to localize faulty points. Accuracy increases. On GCC 1, a pseudo-random radio pulse sequence (SH) from generator 9 through adder 12 and amplifier 14 is fed to the input of a direct communication channel 20. To the other input of adder 12, via switch 7, a siiusoidal signal from generator 4 is supplied. Switching to key 7 is performed by the unit 8 controls At the SFC 16 through the amplifier 17, the filter 19 and the amplifier 18 SHS enters the reverse communication channel 21. At the PMO 1, the received signal through the amplifier 15 and the filter 13 is fed to the input of the correlator 11. To its other input, through the delay block 5 from generator 9. If the signal delay time in block 5 is equal to the signal passing time from generator 9 to LLL 16 and back, the output of the correlator 1I will be a signal with a frequency equal to the frequency of the TFI, and a level that takes one of two values with a frequency equal to key switching frequency 7. The difference of these levels, highlighted ma amplitude detector 6 and the synchronous detector 3 is supplied to the lamp 2. At PMO I osusche-, stvl a timing selectivity qi of signals, coming from separate NUP boiling. Indicator 2 determines the 3rd harmonic attenuation. I il. W GO CO 00 00

Description

The invention relates to telecommunications and can be used on communication lines to measure the non-linear attenuation value at the third harmonic of the path elements — unattended and maintained amplifying points — and to locate faulty amplifying points.

The purpose of the invention is to increase the measurement accuracy.

The drawing shows a structural electrical circuit of the proposed device.

A device for measuring nonlinear distortions in a communication channel contains an indicator 2 at a served amplifying point (GCC) 1, a synchronous detector 3, a generator of a sinusoidal signal 4, a first delay unit 5, an amplitude detector 6, a key 7, a control unit 8, a pseudo-random sequence generator 9 radio pulses, second delay unit 10, correlator 11, adder 12, band-pass filter 13, first 14 and second 15 amplifiers, and on each unattended amplifying plug fHYnjie - first 17 and second 18 linear amplifiers, filter 19, served and maintenance-free amplification points are connected by direct 20 and reverse 21 communication channels.

The device works as follows. at once. I

On the SUP 1, a pseudo-random sequence of radio pulses from the generator 9 through the adder 12 and the first amplifier 14 is fed to the input of the direct communication channel 20. To the other input of the adder 12, a sinusoidal signal from the generator 4 is fed through the switch 7. The switch of switch 7 with a certain frequency is carried out using the control unit B. At the LLL 16, a pseudo-random sequence of radio pulses through the first linear amplifier 17, the filter 19 and the second linear amplifier 18 enters the reverse link 21. The OUP 1 receives the signal through the second amplifier 15 and the band-pass filter 13 to the input of the correlator 11. To the other input of the correlator 11, through the first delay unit 5, a pseudo-random sequence of pulses from the generator 9 arrives. If the delay time of the signal in the first block 5 is delayed equal to the time of passage of signals from the generator 9 to the controlled NUP 16 and back; the output of the correlator of the torus 11 will be a harmonic signal with a frequency equal to the frequency of filling the radio pulse sequence and the level receiving one of two values with a frequency,: equal to the switching frequency of the key 7. The difference between these levels, made using the amplitude 6 and synchronous 3 detectors, is fed to the indicator 2. The control signal to the synchronous detector 3 is received.

through the second delay unit 10, the delay time of which is set equal to the delay time of the first delay unit 5. Thus, at the PMO 1, the time selection of signals coming from the individual LLPs of the trunk is carried out, and using the indications of indicator 2, one can determine the attenuation of the nonlinearity by the third harmonic of the path section from the DPS 1 to the controlled LLP 16, the effect of the nonlinearity of the reverse path is almost eliminated, since it does not pass a sinusoidal signal from generator 4, and the attenuation of filters 19 for a pseudo-random sequence of radio pulses is about 30 dB.

The test signal at the input of the direct communication channel 20 with the closed key 7 can be represented in

the form

and

ex

 A, cosa, t + A cos 63. t,

l - y

where a | - amplitude of the signal of a quasi-random sequence of radio pulses;

U, is the frequency of filling the specified sequence; 2 amplitude sinusoidal

signal; sinusoidal frequency

signal; t -.

The communication channel is described by an amplitude response.

Uebix a, Ug,

.Ubx, 1,

55 where IVUH - output signal;

and,, QI, CJ, are constant coefficients. It is known that in this case the output voltage of the signal frequency CJ is equal to

EI

.ь. «(u, r | a, 4 (1)

xCOS with, t,

and the third harmonic voltage of this frequency

one

and

“S ..) cos3Co, t .. (2)

Let A, "Aj, then the amplitude of the voltage signal of the frequency a, the output of the correlator of the torus 11 is equal to

C, a, A, -f | a, A,., A, (u | A

transition to levels we get

Oiai

R. 20 Ig

07775 20 ig j. 201g / l | -J Al /. With the key open 7 (A 0)

p1 -OSHSG

P, -20lg

the difference between these levels (indicator reading 2)

rr; -r; 2oig (i +1 -jj- Ai).

It is known that

1 1п (1 + х) х - - | + - | - - ...

Since r - A 1 (in communication systems, the nonlinearity is small), then

3 A

2 57 g

thirty

1p10 o

 -e

one

By definition, the third harmonic attenuation

r Pir-P, r 20

where 11, p and p, j. - respectively, the voltage and the voltage level of the main frequency; (and RZG is the same for voltage

and level of the third harmonic, Taking into account formulas (1) and (2)

, V 20 X “201. 5.. -i,.,

4 1 from where

iiA; .4..o.4,

  ..about.

233804

then the scale of indicator 2 can be muted by d values

a, 34.3 - 20f5uP,

5 Determination of non-linear attenuation by the third harmonic of any LLP using the proposed device is possible due to the fact that the voltage of the measured nonlinearity product coincides with the voltage of the CJ frequency signal, in frequency and in phase, which makes it quite definite. law of summation of nonlinearity products from individual elements

 (NUP) tract - the addition of voltage. Therefore, measure successively the values., (Attenuation of the non-linearity of the section from the transmission point to

ten

20

nth nupu and

eggg

(attenuation is not, the linearity of the area from the point of transfer; chi to (n +) - th NUP), you can Determine the attenuation of nonlinearity by the third harmonic (n + 1) -th NUP

W (nft)

where a r,

 34.3 - 20e (P.R.-dR,),

- indication of indicator 2 when measuring attenuation

thirty

LR, Sr,

the same when measuring a.

Claims (1)

Invention Formula A device for measuring non-linear distortions in a communication channel, containing a control unit, a switch, an indicator, a first and second amplifiers, a band-pass filter and a series at a serviced amplifying station. connected pseudo-random radio pulse generator, first delay unit and correlator, the second input of which is connected to the output of a bandpass filter, BbocojoC the control unit is connected to the control input of the key, the output of the first amplifier is the input of the direct communication channel, the input of the second amplifier is the reverse communication channel, at each serviced amplifier point - serially connected first linear amplifier pin to the second linear silicate, the output of which is reverse link input, the input of the first linear pusher is the forward link output, such that j $ In order to increase measurement accuracy, a sinusoidal signal generator, a second delay unit and a series-connected amplitude detector, whose input is connected to the correlator output, and a synchronous detector, are input on the served amplifying point, and the synchronous detector, the output and second input, are connected respectively to the indicator input and the second block output delay, the input of which is connected to the output of the control unit, the output of the generator is 2233806 A signal is connected to the signal input of the key, the output of which is connected to the first input of the adder, to the second input of which 5 the second output of the pseudo-random radio pulse generator is connected, the output of the adder is connected to the input of the first amplifier, the output of the second amplifier of the connectors to the input of the bandpass filter, the control inputs of the first and second delay blocks combined.