SU1383215A1 - Meter for measuring irregularities of delay time - Google Patents

Abstract

The invention relates to a measurement technique and serves to improve measurement accuracy. The meter contains a quartz generator. 1, generators 2 and 3 of the sawtooth voltage and oscillating frequency, phase handler 4, matching cascades 5 and 7, communication channel 6 and indicator 8. Introduction of phase locked loop 9, unit 10 of single-band frequency conversion and the conversion of new functional links provides a measurement of the phase difference between the left and right side components of the spectrum of the test signal. Therefore, the form of the amplitude response will not affect the accuracy of the measurements, since the phase values of the spectral components do not depend on it. 3 il. with e (L

Description

The invention relates to a measurement technique and can be used to measure the unevenness of the group delay time (NGVZ) of communication channels, as well as four-terminal networks,

The purpose of the invention is to improve the accuracy of measurements of irregularities of the group delay time in communication channels with a non-linear amplitude characteristic.

Figure 1 shows the structural diagram of the meter; figure 2 is a simplified spectrum of the test signal; n FIG. 3 is a block diagram of a single-band frequency conversion unit.

The meter contains a quartz oscillator 1, a sawtooth voltage generator 2, a oscillating frequency generator 3, a phase manipulator 4, a first matching cascade 5, a communication channel 6, a second matching cascade 7, an indicator 8, a phase locked loop 9, a unit 10 frequency conversion.

The quartz generator 1 output is connected to one of the inputs of the phase manipulator 4, the other input receives a varying frequency signal from the output of the oscillating frequency generator 3, to the input of which a signal comes from the output of the sawtooth generator 2. The output of the phase manipulator a 4 is connected to the input of the first matching cascade 5, which includes a device matching the transmitting part of the radio links to the communication channel 6, to the input of which the signal comes from the output of the first matching cascade 5, from the output of communication channel 6 The second matching stage 7, which includes devices matching the communication channel 6 and the receiving part of the radio line, is fed to the input of the phase locked loop 9 and to the first input of the single-band frequency conversion unit 10, the outputs of which are Eny with indicator inputs

The single-band frequency conversion unit 10 contains (FIG. 3) two mixers 11 and 12, the first inputs of which are connected to the output of the second matching stage 7, the second inputs are connected respectively to the input and output of the phase rotator 13 by 90 °, the input of which is connected to the output of unit 9, and the outputs are connected respectively

Jq

five

20 25

ZO - Q jс

0

five

with the inputs of the first 14 and second 15. low-frequency filters. The output of the filter 14 through a 90 ° wideband phase shifter is connected to the first inputs of the subtractor 17 and the adder 18, the second inputs of which are connected to the output of the filter 15, and the outputs of the subtractor 17 and the adder 18 are connected to the inputs of the indicator-8.

The meter works as follows.

The signal from the output of the sawtooth generator 2 is supplied to the input of the oscillating frequency generator 3, from its output the frequency fluctuation WQ goes to the first input of the phase manipulator 4, and the frequency s varies from w to CO2, where O) n and respectively the lower and upper limiting frequencies of the communication channel band 6. With the output of the quartz oscillator. 1, the frequency signal I arrives at the second input of the phase manipulator 4, a phase manipulated oscillation is generated at the output of the carrier frequency WQ and the frequency of manipulation SI, which is a test signal whose spectrum does not take into account the components, where k is 2,3,4 ,. .. (figure 2). Moreover, in order to simplify the processing of the test signal at the receiving end, the modulation index may differ from 180. Next, the test signal is connected through the first matching cascade 5, communication channel 6 and the second matching cascade 7 is fed to the first input of the single-sided frequency conversion unit 10 and to the input the phase locked loop 9, at its output, an oscillation frequency njo is formed, which is the reference for the single-band frequency conversion unit 10, in which the right and left sides are separated was iitsih test signal spectrum.

Block 9 phase-locked loop operates on the remainder of the carrier signal s.

In order that the side components with the frequencies w p + L and s - I. do not affect the operation of block 9, its band I CR of the transmission is selected from the ratio „I

h j} and)

and the band I Hold I y4 - D D Ld-deviaci, carrier frequency ..

To facilitate initial synchronization and to reduce dynamic errors, frequency phase-locked loop 9 can be entered into the law of changing the original frequency.

The signal at the input of blocks 9 and 10 has the form

Xg (t) Asinwot + Bsin (tOo-il) + Bsin (w +) t + 1 / „p,

H.

Tjp

(t) - sin (a t + (l) BC

(2)

+ - sin (nt + and „).

np

Ha the output of the adder 18 as a result of the summation of the expressions (1) and (2) we get

U (t)

-2 sin (5lt + v ,,

where (/ and if, respectively, the phases of the left and right sides of the input signal components.

The signal at the output of the mixer 11 as a result of multiplying the signals will be

and.

(t) I Asinui t + Bsin X

x (u) j-fl) t- t J + BsinC (u) o + L) t + i / np

ACBC

CsiniOj t -2- (1-cos2u) ot) + -r-V

4cos (l (fo-fl-jxr) t - 1 / l1-co8 (2u) (, - fl) tI A 11+ Y C, + LH t + Vnpl -cos (2U) - “- fl) t + 1 / „p.

Ha filter output 14 low frequency

Rr if, (t) - cos (At + (fi,) +

+ cos (at +% p).

Ha the output of the phase shifter 16 90 get

and

xsin (ilt

(t) 2 sin (ftt + (A) + -2 1/2.

+

The output of the mixers 12 signal is described by the expression

(, „, Asinu), t + Bsint (u) -il) t-l / + + Bsint (u) j + SDt + costdt Rr

 .ACsin2Upt (; -fl -kr) t - 41, + -h: sin (2u), - i-) t- lf, -f - | x

4sini; (+ fl-j-r) t + + sint (2u) + Sl) t + (.

Ha filter output 15 low frequency signal will be

At the output of the subtractor 17 as a result of subtractions (1) and (2) we get

HP

Ug (t) -2- sin (yes + H L)

at

tс90

one)

/ +

41, +

c20

25

thirty

40

45

55

Thus, at the outputs of the single-band frequency conversion unit 10, we obtain two oscillations of the same frequency I, but with phase shifts corresponding to the phase characteristic of the communication channel, which arrive at the inputs of the indicator 8, where the phase difference between them is measured by one of the known methods . At the same time, this phase difference is proportional to the non-uniformity of time during the delay of the communication channel.

In comparison with the known, the proposed measure of the nonuniformity of the group delay time allows an increase in the measurement accuracy. in channels with non-linear amplitude response, due to the fact that in it the NGVZ measurement process consists in measuring the phase difference between the left and right side components of the spectrum of the test signal. Consequently, the form of the amplitude response will not affect the accuracy of the measurements, since the phase values of the spectral components do not depend on it.

In addition, all the basic elements of the meter can be implemented on the basis of elements of digital technology, which allows to significantly reduce the size and reduce the cost of the device.

50

Claims (1)

Invention Formula A non-uniformity meter for the group delay time, containing a quartz oscillator, a sawtooth voltage generator, the output of which through the oscillating frequency generator is connected to the first input of the phase manipulator, the output of which connected to the input of the first matching cascade, the output of which is connected to the input of the second matching cascade through a communication channel, and an indicator characterized in that, in order to improve the measurement accuracy of the irregularities of the group delay time in the channels, in connection with a linear amplitude characteristic, It is equipped with a phase locked loop and a single band frequency conversion unit. Phi The output of the crystal oscillator is connected to the second input of the phase switch, the output of the second matching stage is connected to the first input of the single-sided frequency conversion unit and to the input of the phase-locked loop module, the output of which is connected to the second input of the single-band conversion unit, the first output of which is connected to the first the input of the indicator, and the second output - with the second input of the indicator.