SU1184108A1 - Meter of parameters of television signal - Google Patents

Description

The invention relates to television technology and can, in particular, be used to measure the levels and anti-noise processing of the distortion of the television signal.

The purpose of the invention is to improve the accuracy of measurement parameters of the television signal.

Figure 1 shows the structural electric circuit for measuring parameters of a television signal; FIG. 2 shows timing diagrams explaining the operation of the meter in the measurement mode of differential distortions; 1; on fig.Z - timing diagrams explaining the operation of the meter in the mode of measuring nonlinear distortion; 4 shows time diagrams explaining the operation of the meter in mode 2 of measuring the non-uniformity of amplitude-frequency characteristics; figure 5 - timing diagrams explaining the operation of the meter in the mode of measuring the level of fluctuation-2 fur.

The parameter of the parameters of the television signal contains a block 1 automatic gain control, a block 2 processing a television signal, a control block 3, a driver 4 control pulses, a correction block 5, an amplifier 6, a shift register 7, a driver 8 pulses, a generator of 9. tact pulses, block 10 frequency and phase control, computing unit 11 and analog-to-digital converter 12, indicator 13, block averaging 14, consisting of keys 15-1 - 15-п, 16-1-д 16-η and capacitors 17-1 - 17 -P.

In the mode of measurement of differential distortions, a signal arrives at the input of the meter (Fig. 2a, t) ₁ where in the diagram a the signal is depicted on the _4th scale of the television fields, and on the diagram m - on the scale of the lines).

The signal I (Fig. 2) is affected by fluctuation and background noise and contains a test signal in the active part of the frame or in the interval of i.e., feed lines. At the same time, a command is sent from the control unit 3, which includes the automatic gain control unit 1, which, comparing the sync signal with the reference voltage of a given value, sets the television signal nd (figure 2) of its standard value at its output, which is fed to the processing unit 2 , which is a serial connection of a band-pass filter tuned to the center frequency and an amplitude (phase) detector. In the bandpass filter, the color subcarrier g is selected from the signal g (Figure 2) (figure 2). Amplitude detector detects. the color subcarrier extracted from the signal cx (Fig. 2) in the measurement of the differential gain, and the phase detector in the measurement of the differential Phase.

As a result, the output of the processing unit 2 is a signal e.

(Fig.2), which corresponds to the envelope of the signal E (Fig.2) or a change in the phase of the subcarrier. In this case, each part of the signal in the interval of the signal line e (Fig. 2) corresponds to the law of phase change in the corresponding color signal subcarrier packet <E (Fig. 2). The signal e (figure 2) is supplied to block 14 averaging, in which the keys 15-1 and

16-1 are opened by pulses ^ - (figure 2), keys-15-2 and 16-2 - by pulses and (figure 2), etc., up to the last pair of keys 15-p and 16-p, which are opened impulses to (figure 2). In this case, capacitors 17—1-17-s are charged with signal samples ε (FIG. 2) with a time constant defined by the output resistance of the processing unit 2 and capacitors 17-1 through 17-P.

As a result, constant voltages are formed on the capacitors 17-1 17- η, which are proportional to the average values of the corresponding signal samples

B (figure 2), and at the input of the amplifier 6 step signal m. (Figure 2), the envelope of which coincides with the mathematical expectation of the signal e / figure 2). Those. At the input of the amplifier 6, the envelope (shape) of the distortion of the television signal is formed; in this case, this distortion is a differential gain (differential phase). The signal number (figure 2) after amplification in the amplifier 6 is fed to the output of the meter.

The magnitude of the distortion of the television's signal (in this case, the magnitude of the differential distortion) is determined as follows.

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The voltage from the capacitors 17-1 17-p is supplied to the computing unit 11, in which the keys are alternately opened by pulses from the microprocessor, and the voltages from the capacitors 17-1 to 17-n are alternately passed to the analog-to-digital converter 12, in which The maximum and minimum voltages of a variety of voltages with capacitors 17-1 are 17-17. Next, the difference between the maximum and minimum voltages in a digital form, which is fed to the indicator 13, is determined. Thus, at 15

The indicator 13 indicates the magnitude of the distortion, and at the output of the amplifier 6 a form of the same distortion (differential distortion) is formed.

Simultaneously with the formation of 20

signal l \ (figure 2), i.e. forms of distortion, and the calculation of the magnitude of the distortion signal u (Fig.2) is fed to the driver 4 control pulses, which, at the command of block 25 3. control from the signal a. (Fig.2) generates synchronization pulses g (Fig.2) with a line frequency and gating pulses 5 "(Fig.2) on a scale of 7 television fields or (Fig.2, c) on a scale of rows (with a frequency of television fields and duration of m-lines).

The fronts (positive gradients) of the pulses W (Fig. 2) set the shift register 7 to the zero initial state. In addition, the pulses are fed to the generator 9 and are allowed to produce a burst of pulses, l (figure 2). Each of the packets is located relative to each of the surrounding 40 distortion in the signal e (Fig. 2) so that they are superimposed on each other, i.e. match in time. Moreover, each of the signal packets, l (figure 2) consists of d pulses, 45 ie, the number of pulses in a packet is equal to the number of capacitors 17-1 to 17-n, and in each packet the first of η pulses has a zero phase. The pulse repetition frequency in the signal packets l is set from the block 10 by a signal in the form of a constant voltage of a certain value, which is specified by the signal sweep to or B (Fig. 2) coming from the 55 control pulses of the shaping pulses.

The signal in (figure 2), formed PS swing in block 10, enters

generator 9, which generates a 'pulse packet d only in the case when the positive values of the signals in and f (figure 2) coincide.

In those cases when the meter does not require gating of the measurement site, i.e. no signal required

5 (FIG. 2) at the command of block 3, in the imaging unit 4, a series of pulses is generated, which is decrypted in block 10 and allows to generate a certain constant voltage supplied to the generator 9.

Packages of pulses l are fed to the imaging unit 8 pulses and the input of the shift register 7. In the driver 8 pulses from each of the first pulse in each packet of the signal l is formed a pulse, resulting in a sequence of pulses y (figure 2), which is fed to another input of the shift register 7. At the first output of the shift register 7, pulses y are obtained (Fig. 2), on the second, pulses and (Fig. 2) shifted by one period relative to the pulses -a ,, at the third output, pulses shifted by two periods, and so on. d. At the last output of the shift register 7, pulses are received to (Fig. 2), shifted by (η — 1) periods. Each of the η signals goes to the corresponding key pair 15-ί and 16— ΐ, where L = 1,2, .., n, in block 14, the sample-averaging and opens them with positive values.

To ensure collaboration, the amplifier 6 and the computing unit 11, at the command of the control unit 3, applied to the correction unit 5, in the last of the pulses% (FIG. 2), a pulse signal is generated that sets certain transmission coefficients in the amplifier 6 and the computing unit 11 and decisive indication of the signal at the output of the amplifier 6 and the magnitude of the distortion on the indicator 13. Such control of the amplifier 6 and the computing unit 11 is caused by the fact that, for example, when the position of the strobe signal changes.% (FIG. 2) transient percentages begin ssy-sample averaging in block 14, amplifier 6, the computing unit 11 and the display 13. The time constant of the transient reaches several seconds, and the measurement results can be incorrect otschita5

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therefore, a ban is imposed on the indication of the shape and magnitude of the distortion for the maximum transient time. Transients also include the search for extreme values of voltages from capacitors 17-1 to 17-V and the calculation of the difference between the extreme values in the computing unit. eleven.

Thus, in the considered mode, measurements of differential distortions in a television signal affected by noise are provided, and the measurement result is the envelope (shape) of the distortion and the magnitude of the distortion in the form of a digital reference.

I

In the nonlinear distortion measurement mode, a differentiating chain is used as a processing unit 2. To the meter input, i.e. The automatic gain control unit 1 and the test pulse driver 4 receives a test television signal ((FIG. 3) on the scale of television lines (all signals in FIG. 2 are shown on the line scale). The meter in this mode works the same way as in the mode of measuring differential distortion with the following refinements. Signal a (fig.Z) after processing block 2 looks like a signal £ (fig.Z). The frequency in the generator 9 is set such that in each batch of pulses

g (fig.Z) contains five pulses, i.e. as much as the steps in the signal “c” (FIG. 3) for one line. The signal s (FIG. 3) is produced in the driver 4 of the control pulses, which sets the shift register 7 to zero initial position with its fronts and for positive values in the generator ’9 the generation of a sequence of pulse packets g is allowed (FIG. 3).

At the output of the pulse shaper 8, pulses are generated фиг (Fig. 3), corresponding in duration and position to the first periods of pulse oscillations in · pulse packets g (Fig. 3). The pulses d (fig.Z) are fed to the shift register 7 and under the influence of the pulse packets g (fig.Z) fed to another input of the shift register 7, to the first register output

7 of the shift, pulses d (FIG. 3) pass, on the second, pulses e (FIG. 3), etc., and the pulses (FIG. 3) that control the keys 15-ί and 16-1 to block 14, averaging.

As a result, constant voltages are formed on the capacitors 17-1 - 17-c, corresponding to the average values of the steps of the input signal a (Fig. 3). At the output of the amplifier 6, a signal y is obtained (FIG. 3), and the indicator 13 indicates the magnitude of the difference between the maximum and minimum steps.

In the mode of measuring the non-uniformity of the amplitude-frequency characteristic, a peak detector with a reset is used as the processing unit 2, which from the input signal m (FIG. 4) forms pulse packets 5 (FIG. 4). The swing of each pulse in the packet of pulses 5 (figure 4) is proportional to the swing of the corresponding packet of the input signal "

(figure 4). Next, the meter works in the same way as in the mode of measuring nonlinear distortions (the signals shown in figure 4, c, d, are the signals at the outputs of the shift register 7, and the signal at figure 4 is the signal at the output of the amplifier 6) .

In the measurement mode of the transfer of rectangular pulses, the processing unit 2 is made in the form of a resistor providing the necessary time constant in the unit 14 of the sampling-averaging device. Further, the device works similarly to the first mode of measuring differential distortions with the only clarification that the pulses ^ (figure 2) coincide with the beginnings, and the pulses of (figure 2) - with the ends of the flat tops of the measured rectangular pulses.

As a result, on the indicator 13 is displayed the swinging angle of the apex of rectangular pulses. Λ

In the mode of measuring the fluctuation noise level, the processing unit 2 is a serial connection of the level fixing unit and the limiter. The cc input signal (FIG. 5) is converted to a signal §

(Fig.5) in block 2 processing. The meter in this mode works in the same way as in the mode of measuring the differential of ⁷ 1 general distortions with the following refinements. The signal e (Lig.5) is equivalent to the signal ^ (FIG. 2) and is phased so that its entire duration falls into the portions of signal b (FIG. 5) without 5 fluctuation disturbances. The signal, g (figure 5) is equivalent to the signal. and (Fig. 2) and is located above the signal areas 5 (Fig. 5), With fluctuation disturbance, the noise voltage swing Oil. / 2.

As a result, a reference voltage is formed on the capacitor 17-1, which corresponds to a zero value of the fluctuation noise, and 17-n capacitors - 17-n - constant voltages proportional to the effective value of the fluctuation noise, whose span is 0 _W / 2. Because

, the voltages on the capacitors 17-2 17-d are the same, the indicator 13 indicates the magnitude of the fluctuation disturbance proportional to the voltage difference from one of the capacitors 17-2 to 17-n and from the capacitor 17-1.

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Claims (2)

A TV SIGNAL PARAMETER METER containing a television signal processing unit, a control pulse generator, the first input of which is connected to the first output of the control unit, a computing unit, an analog-to-digital converter and an indicator, which, in order to improve the measurement accuracy of the television signal parameters, an automatic block is entered gain control, correction unit, sampling-averaging unit, shift register, amplifier, pulse shaper, clock and block generator to frequency control and phase, with the block automatic gain control, information ^; the dione input of which is the input of the television signal meter, the processing unit television signal, sampling-averaging unit and amplifier are connected in series, control driver, frequency and phase control unit, clock generator, pulse generator and shift register are connected in series between the input of the television signal parameter meter and the corresponding inputs of the sample-averaging unit, second output unit control unit is connected to the control input of the automatic gain control unit, the third output is connected to the control input of the television processing unit signal, and the fourth output - to the control input of the correction unit, the output of which is connected to the control inputs of the amplifier and computing unit, the information inputs of which are connected to the corresponding outputs of the sample-averaging unit, and the output through the analog-digital converter to the indicator input, the second output of the driver control pulses connected to the information inputs of the correction unit, shift register and clock generator, the output of which is connected to the second control input of the shift register. ZI, 1184108 > 1184108 2