SU143907A1 - A method for measuring the distortion of the horizontal part of the transient response curves of test signals - Google Patents

Description

In auth. St. No. 129686 describes a method for determining the ratio of a signal to a quasi-peak value of an interference by evaluating this ratio on an oscilloscope when the visible bounds of the lower and upper interference peaks match.

In accordance with this method, this coincidence is accomplished by introducing calibrated pulses of reverse polarity at controlled points in the television path, creating simultaneously a mobile luminous mark on the receiving screen at the location where the desired ratio is measured.

The subject of the present invention is the application of the method described in ed. St. No. 129686, for measuring the distortion of the horizontal part of the transient response curves of test signals.

When measuring these distortions, oscillographic level meters (calibrators) are commonly used, which allow directly determining the ratio, for example, of the magnitude of the burst or slope to the magnitude of the signal Ug.

However, when the indicated distortions are small (2-5%), their reading with such devices becomes difficult and the measurement accuracy decreases. In some cases, to improve the observation of distortions on the horizontal part of the pulses, as well as to measure their magnitude, the lower part of the signal is cut with the help of a limiter, and the remaining part after amplification is viewed on an oscilloscope. However, the direct reading of the desired ratio

No. 143907, -2 is difficult and the magnitude of the distortion is determined using a grid, which leads to measurement errors due to parallax.

Application of the method described in ed. St. No. 129686, in which calibrated pulses of the inverse polarity signal are applied to the i ccjjp yeMQro signal circuit, improves the accuracy of measuring the distortion of the horizontal part of the transient response curves of the test signals when they are played on a cathode oscilloscope screen.

FIG. 1 shows a block diagram of an apparatus for carrying out the method according to the invention; FIG. 2, o – e, curves are shown that clarify the essence of the latter.

The signals for which the distortions are to be measured are fed to the input terminal 1 (Fig. 1), and then to the mixer 2 and to the cascade 3. In the cascade, using a calibrated phase shifter, a smooth change in the temporal position of the front (or rear) front can be performed test-signal within the period of its repetition. Generator 4 generates compensating square-wave pulses following the frequency of the test signal. The duration of these pulses can be adjusted, and the position of their leading edge is determined by the temporal location of the synchronizing pulses after stage 3.

At the output of the amplifier-limiter 5, compensating pulses of positive and negative polarity are created, which enter cascade 6, in which the magnitude of the compensating pulses fed to the input of mixer 2 is changed by the regulator and measured with a switch or, to increase the accuracy of measurements, it is regulated calibrated attenuator. From the output of the mixer 2, the test signals, mixed with square compensating pulses, are sent to the limiter 7, and then to the output stage 8. To the output terminal 9, an oscilloscope is attached, on the screen of which measurements are made. The horizontal scanning of the oscilloscope is performed either by the output signal of the device, or the clock pulses from its intermediate stages are used.

Suppose that the waveform of the distorted signals has the form shown in FIG. 2, a. The position and duration of the compensating pulses, by appropriate adjustments of the cascade 3 and generator 4 (Fig. 1), are set so that they are located relative to the waveform diagram of the signals, for example, as shown in Fig. 2. 2, b. The magnitude of the compensating pulses is controlled, for example, by changing the attenuation of the calibration attenuator 6 (Fig. 1) until the coincidence of the distorted part of the pulse coincides with the control, the level of its undistorted part (Fig. 2, c).

In order to increase the accuracy of measurements using limiter 7, the lower part of the signal is cut off, for example, at level AB of FIG. 2, b).

The remaining portion of the signal is greatly enhanced and observed on an oscilloscope, as shown in FIG. 2, d. When the distorted part of the signal is touched with the control line 00 on the oscilloscope (the compensating signal is equal to the magnitude of the burst At /), it is noted by the position of the scale of the calibrated attenuator (or the pointer instrument) 6 (Fig. 1). Limiter 7 is then turned off (or used to cut off the top of the signals). The attenuation absorbed by the attenuator is reduced until the compensating signal ensures that the upper part of the signal is aligned with the lower control level (Fig. 2, e). In this case, the compensating signal is equal to the signal f / o. The ratio is determined, for example, directly in decibels, as the difference in readings on a scale of a calibrated attenuator or a switch instrument at times corresponding to, and FIG. 2, g and d.

In a similar way, the distortion in the form of the slope of the horizontal part of the pulses is estimated.

The proposed method can also be used to measure time intervals between individual points of test signals, for example, to measure their duration, rising fronts, etc.

In this case, the compensating pulses from the output of the cascade 6 (Fig. 1) can be applied to the control, and the oscilloscope's cathode-ray electrode to create a brightness mark on the test signal. The time intervals are counted on a scale of a calibrated phase-shifter 3 (Fig. 1), shifting the luminous mark within the required limits.

Subject invention

Application of the method according to ed. St. Ni 129686 to measure the distortion of the horizontal part of the transient response curves of test signals when they are reproduced on the screen of a cathode oscilloscope by applying a calibrated impulse to the circuit of the test signal inverse to the polarity signal.

-3- № 143907

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