SU425133A1 - MEASURING THE DISTORTIONS OF A FLAT TOP OF RECTANGULAR TESTING PULSES - Google Patents

Description

one

The invention relates to a measurement technique and can be used to automatically measure the distortion of rectangular test pulses.

Devices are known for automatically measuring the voltage by a compensation method using a sweep balance with a rampomer-step change in the compensation value. The known device contains a discrete scanning converter of the measured voltage into a numerical pulse code and a pulse counter. During each cycle, a pulse counter converts the number of pulses into a digital decimal code convenient for controlling a digital recorder.

With the aid of a known device, it is possible to measure a constant voltage or, using an intermediate conversion of a pulse voltage to an equal constant voltage, measure the pulse width. However, when measuring, it is often necessary to measure the relative magnitude of the distortions expressed in the skew of the horizontal vertex of the rectangular pulses. Such measurements are relevant in the pulse technique, in determining the distortions of the video signals passing through the transmitting circuit, and in television technology, where

by the magnitude of the decay of the test signals, a decrease in luminance during the transmission of the line is judged. Until now, an oscilloscope is used to perform such measurements. The process of measurement is laborious, requires qualified personnel, is not amenable to automation and has a large error. The measurement result cannot be represented in a digital code for its machining.

The purpose of the invention is to improve the measurement accuracy by eliminating a subjective error and automatically measuring the relative magnitude of distortions of a flat top of rectangular test signals with indication of measurement results on a digital indicator and outputting measurement results in a digital code.

The essence of the invention is used as a reference papr voltage for generating the compensating sigpala constant papr voltage obtained from the peak value selected undistorted signal to deploy balancing magnitude distortion by using a compensating value in the form of uniformly-decaying stepped voltage with a duration of steps equal to the period test signal, as well as limiting the measurement time by compensating for the amount of distortion. FIG. 1 shows a block diagram of the proposed device; in fig. 2 - graphics, according to your device. The device contains a control pulse shaping circuit 1, a level fixing unit 2, an amplitude limiter 3, a clock pulse generator 4, a signal peak value extracting unit 5, a level fixing unit 6, a strobe pulse generating unit 7, a quantizing device 8, a switching device 9, a circuit Comparison Yu, generator AND stop pulses, coincidence circuit 12, key circuit 13, counting device 14 and digital indicator 15. The device operates as follows. The input of the meter receives distorted rectangular test pulses (Fig. 2, a). The control pulse shaping circuit 1 generates the following pulses: the control pulses of the level fixing unit 2, located directly in front of the leading edge of the test signal (Fig. 2.6); 4-clock pulses for starting the generator, located between the test signals; control pulses of the level fixing unit located between the test signals. The level fixing unit 2 fixes at the level (Fig. 2, c) a portion of the signal located directly in front of the leading edge. The peak value extracting unit 5 generates for the quantizing device 8 a constant reference voltage equal to the span of the undistorted portion of the signal (Fig. 2, c, dashed lines). The quantizing device 8 is controlled by clock pulses from generator 4. The output voltage of the quantizing device, representing a step voltage with a discretely decreasing amplitude, the period of one step of which is equal to the period of the following clock pulses (Fig. 2, d, dashed line), is fed to one From the inputs of the comparison circuit 10. A distorted signal is received to the other input through the controlled level fixing unit 6 (Fig. 2, d). The fixation level is set so that the maximum value of the distorted signal is close to the magnitude of the reference signal, but does not exceed it. Such a fixation of a distorted signal makes it possible to reduce the measurement time to the minimum possible. The comparison circuit 10 conducts an amplitude comparison of the instantaneous values of the step voltage and the distorted signal during each clock cycle (Fig. 2, d). When the two voltages are matched, the comparison circuit generates pulses, the duration of which depends on the magnitude of the excess signal voltage over the voltage of the step (Fig. 2, e) during each clock cycle. The first pulse acts on the switching device 9, which unlocks the key circuit 13 (FIG. 2, i). The clock pulses from the generator 4 begin to pass through the key circuit 13 to the counting device 14 (Fig. 2, k) during the whole time of the distortion compensation. The trailing edge of each pulse of the comparison circuit 10 is started by the generator 11 of the stop pulse, and the short pulses, whose temporal position during each clock cycle is determined by the moment the comparison ends (Fig. 2, e). The strobe-pulse formation unit 7 by the trailing edge of the test signal generates pulses that arrive at the input of the coincidence circuit 12 (Fig. 2, g). With a temporary coincidence of the pulses at the inputs of the coincidence circuit 12, a pulse is produced (Fig. 2, h), which controls the end of the count. This pulse acts on the second input of the switching device 9, which locks the key circuit 13. The access of the clock pulses to the counting device is stopped, the measurement cycle ends. On the digital indicator 15, a measurement result is recorded equal to the number of clock pulses that have passed through the key circuit 13 during the compensation time. Since each clock pulse corresponds to a change in the reference voltage by a specific value of the quantization value, which is a certain part of the reference voltage, the fixed number of clock pulses corresponds to where the Avon is the specific value of the quantized voltage; n is the number of clock pulses counted by the counting device during the comparison time. Since / Z-Avon Av, and Vj: Vj (see Fig. 2), the measurement result before Av is directly the value. With a specific quantization value of one or one tenth of a percent, the result of measuring the ratio is expressed directly in percent. The invention The distortion meter of a flat top of rectangular test pulses, comprising a control pulse shaping circuit connected to a generator of such pulses connected to a quantizing device, a comparison circuit and a serially connected key circuit, a counting device and an encoder, which is different in that accuracy and automation of the process of measurement, it introduced two blocks for fixing levels, a block for selecting the peak value of the needle, an amplitude limiter, The switching device, the stop pulse generator, the strobe pulse shaping unit and the coincidence circuit, iriche, the meter input through a serially connected level fixation block and a peak value selection block are connected to the input of a quantizing device and through an amplitude limiter and a second level fixation block with the comparison circuit input , the output of the amplitude limiter through the gate-pulse formation circuit is connected to one of the inputs of the coincidence circuit, the second input of which through the stop pulse generator c It is connected with the output of the comparison circuit, and the output of the comparison circuit and the output of the matching circuit are connected to the inputs of the switching device, the output of which is connected to the potential input of the key circuit.

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