SU1570030A1 - Method of measuring interference in television channel - Google Patents

Abstract

A method for measuring interference in a television channel involves transmitting a television signal on a television channel, in free intervals of stubble fields, which, on the receiving side, generate samples, which, in turn, determine the second central moment M ₂ and the effective value of fluctuation interference. The aim of the invention is to expand the functionality of the method by providing separate measurements of the parameters of fluctuation and sinusoidal interference (or two sinusoidal interference), which is achieved by determining an additional fourth (or fourth and sixth) central moment of the set of samples of the television signal and then calculating the effective value of fluctuation interference and amplitude sinusoidal interference with the appropriate formulas. 1 hp f-ly, 2 ill.

Description

The invention relates to television technology and can be used in automatic digital measuring parameters of television channels.

The purpose of the invention is to enhance the functionality by providing separate measurements of the parameters of fluctuation and sinusoidal interference.

FIG. 1 shows the structural electrical circuit of the device for implementing the method for measuring interference in the television channel J in FIG. 2 — timing diagrams explaining the essence of the method.

A device for implementing a method for measuring interference in a television channel contains a 1 row selector, a multivibrator 2 delays, a sawtooth voltage generator 3 (GPN), a limiter 4, an interval multivibrator 5, a pulse packet generator 6 (HSH element I 7, a pulse counter 8, a driver 9 gating pulses, switch 10, sampling-storage unit 11, analog-to-digital converter (ADC) 12, computing unit 13, digital-analog converter (PDP) 14, 15 field counter, key 16, display unit 17 and weighing filter 18.

A method for measuring interference in a television channel is as follows.

On the transmitting side of the television channel, a television signal is generated, which is then transmitted through the television channel and mixed with the fluctuation and sinusoidal signals.

cl

00

3 15

Furs (phi) Go2a) „are fed to the input of the device for implementing the method (FIG. 1). On the receiving side of the television channel, in the intervals of the lines of damped field pulses free from the transmission of service signals (lines 22- and 335- according to GOST 7845-79), the samples of the mixture of the television signal and interference are counted. This operation is performed as follows. In the selector 1 of the line (Fig. 1), a sync pulse corresponding to the beginning of the 22nd or 335th (depending on the even-odd half-frame) rows is selected. The selected sync pulse triggers Multivibrator 2 delays, at the output of which a pulse is formed (FIG. 2b) whose falling edge triggers GPN 3 The output signal of GPN 3 (FIG. 2b) is fed to one of the limiter inputs, 4, to the second input of which arrives at the reference the level that determines the moment of occurrence of the leading edge of the output

more than a period of sinusoidal interference, and the time of formation of samples moves discretely within an interval exceeding the period of the lowest-frequency sinusoidal interference, for example, according to a random law. the condition is implemented as follows. The leading edge of the output pulse of the multivibrator 5 starts the GUI 6, which forms a packet of M rectangular pulses, the follow-up period of which is ut (FIG. 2d). The pulse packet of the GUI 6 is summed with the output signal of the multivibrator 2 in the element And 7 and is fed to the counting input of the counter 8 pulses having a counting module equal to

the number of pulses in the package GUI 6, i.e. equal to Mo. Thus, in each field, M + 1 impulse goes to the input of counter 8, and switching the high bit of counter 8 takes place —in each field offset from

Whose signal limiter 4. Output 25 previous sex by the value of ut

the signal of the limiter, in turn, triggers the multivibrator 5 interval, at the output of which a pulse is formed (fig.2g), corresponding to the interval T, during which the next reading of the input signal is formed. The duration of the interval T is longer than the period of the lowest frequency measured sinusoidal disturbance, which is a value of at least 5 x for a sinusoidal disturbance with a spectrum higher than 0.2 MHz. The samples of the television signal mix and interference are formed by the sampling-storage unit 11 from the input signal coming to the block 11 through the switch 10. The samples of the television signal mix and the noise come from the output of block 11 to the signal input of the ADC 12, and from its output to one of the inputs computational block 13, in which the accumulation of counts is made and their statistical characteristics are calculated (central moments Kj, M4, K6), and then, based on them, the effective value of the fluctuation interference and the amplitudes of sinusoidal interference. The results of the calculations are displayed by the display unit 17.

The purpose of the invention is achieved if the average period of formation of samples of the input signal is much

(possible switching times are shown in dots in fig.2d). The output signal of the counter 8 starts the gating pulse shaper 9, Forming short duration pulses to control the operation of the sampling-storage unit 11

Figures 2e, ga show the positions of the output pulse of the multivibrator 5 and the gate pulse in the interval following the field examined. Moving the beginning of the interval T according to a random law is achieved by applying to the second input a limiter 4 of the restriction level, which changes according to a random law under the control of the computing unit 13.

In addition, the output pulse of the multivibrator 5 is fed to the strobe input of the A / D converter 12 to synchronize the conversion time along the falling edge of the pulse of Fig. 2d (Fig. 2e).

Field counter 15 has a counting module of 2N, where N is the required sample size to obtain a reliable measurement result. Counter 15 is started by pulses from the output of multivibrator 2.

Computing unit 13 calculates the central moments of the formulas

one

T

H

M4

Jl

IF

z

N reports

input signal.

where x {,

From the calculated central moments, the amplitude value of the sinusoidal interference Un is then calculated by the formula

U0 8 (M - M4 / 3)

and the effective value of the fluctuation disturbance according to the Formula

ieff L | M2-.,

 EP

The sixth central moment is used in the separate measurement of the amplitudes of two sinusoidal interferences U, and Uj, and the effective value of the fluctuation disturbance U

Sought values in

this case is calculated from the system of equations

+ (U + U) / 2 M

2

UG 8 (M2-M4 / 3);

and

4- U - (M4-2M)

In addition, the device can measure the frequencies of one or two sinusoidal interference through the transfer characteristic of the weighing filter 18.

If you determine the amplitude of the sinusoidal noise without the weighing filter and with it, then using the ratio of the obtained values, you can determine the frequency of the sinusoidal noise. With such measurements, the key 16 is closed, through which the switch 10 receives impulses from the high-order output of the counter 15. As a result, for N fields the television signal passes to the input of block 11 directly, and for the next N fields through the weighing filter 18,

The required measurement accuracy of the effective voltage of the fluctuation noise and the amplitudes of the sinusoidal noise is determined by the choice of the sample size N. In the case of the absolute mean, the non-quadratic methodical error of measurement of these quantities is -. It is no more than 3% of the effective voltage of the total interference, and for N it is no more than 27, of this effective voltage, the error is 0

five

0

five

0

The frequencies of sinusoidal interference are unambiguously determined by the error in the estimation of their amplitudes.

Claims (2)

1. A method of measuring interference in a television channel, comprising transmitting a television signal on a television channel, generating samples of a television signal transmitted on a television channel in intervals of damping field pulses free from signaling service signals, determining the second central moment Kg by the generated samples and determining the effective fluctuating noise value, that is, so that, in order to expand the functionality of the method by providing separate Measuring a parameter fluctuation, and sinusoidal interference, simultaneously with the second central moment M2 is generated by television signal additionally counts determined fourth central moment. with the subsequent calculation of the amplitude value of the sinusoidal interference U0 by the formula IL 8 (M-ML / 3) About v 2 and the effective value of the fluctuation disturbance is calculated by the formula U 40 R  | m- - ЈЈ / 2, five five 0 moreover, the point in time at which the television signal samples are formed varies from field to field within an interval longer than the period of the lowest frequency measured sinusoidal noise, and the beginning of the specified interval move randomly. 2. The method according to claim 1, characterized in that, in order to separately measure the effective value of the fluctuation interference and the amplitudes of the two sinusoidal interference, simultaneously with the determination of the second and fourth central moments K and M, the generated central moment My , and the effective value of the fluctuation space - XH UgqxpH amplitudes U, and 114 of the two sinusoidal interferences is calculated respectively by the system of equations V fl. V +) / 2 M2; U + U 8 (); uf + U6ft -i M6-I2M2 (M4-2M), yy (t) streha  restrictions ii -LA dr dt