SU718806A1 - Arrangement for measuring transient characteristics - Google Patents

Description

one

The invention relates to a measurement technique and is intended to measure the transient characteristics of four-port networks.

A device for measuring the transient characteristics of magnetic recording equipment is known, which implements a method that contains a series-connected reference generator, a measuring binary pseudo-random signal generator, an adder, a quadrupole under test (magnetic recording equipment), a band-pass filter, a driver, a delay unit, a control binary pseudo-random signal generator, and a correlator whose second input is connected to the output of a quadrupole 1 via a notch filter.

Its disadvantage is the limited measurement capabilities, due to the measurement of only an exponentially increasing transient response due to the adjustment of the delay in the channel of the reference sinusoidal signal.

It is also known a device that implements a method that contains a reference generator and a generator of a measuring binary pseudo-random signal, the signals of which are recorded on a magnetic tape, and then reproduced; shaper, delay unit, pilot binary pseudo-random signal generator and blaster 2.

The disadvantage of this device is a significant measurement time.

The aim of the invention is to automate measurements.

The goal is achieved by the fact that in a device containing a reference generator, the output connected via a pseudo-random sequence generator to one of the device inputs, is a correlator, one of the inputs of which is connected to another device input, and the second input of the correlator is connected to the output of the control generator of a pseudo-randomly sequence, A reference reference generator and a sync pulse unit are introduced, one of the inputs of which is connected to the second output of a pseudo-random generator, and its other

the input is connected to the second output of the control pseudo-random sequence generator, the input of which is connected to the output of the control reference generator. The drawing shows a block diagram

devices.

It contains the reference generator 1, the correlator 2, the pseudo-random signal generator 3, the exhausted four-pole 4, the control reference generator 5, the control generator 6 of the pseudo-random signal, the sync pulse unit 7, the inputs 8 and 9 of the device.

The device works as follows.

Generators 3 and 6 of pseudo-random signals, triggered respectively by reference generators 1 and 5, produce the same pseudo-random sequences. These sequences, due to the insignificant difference in the frequencies of the reference oscillators 1 and 5, slide relative to each other.

Thus, a variable delay is created between the pseudo-random sequences, which are generated by the generators 3 and 6 of the pseudo-random sequences.

The pseudo-random sequence from the output of the generator 3 of the pseudo-random sequence passes through the tested quadrupole and correlates with the control pseudo-random sequence generated by the generator 6.

The voltage at the output of the correlator is proportional to the value of the pulse characteristic of the tested quadrupole. The same voltage is determined by the mutual correlation function between the pseudo-random sequences that are generated by the generators 3 and 6 of the pseudo-random sequences.

Since the sequences slide relative to each other, at the output of the correlator, the voltage varies in accordance with the change in the impulse response of the test quadripole.

The spectrum of the signal observed at the first output of the device is transformed into the low-frequency region but compared with the spectrum of the impulse response of the test quadripole, and the signal itself is periodic. This greatly simplifies the further processing of the low-frequency voltage at the output of the correlator.

The degree of transformation is determined by the difference between the frequencies of the reference oscillators and the length of the pseudo-random sequence, the discrete duration of the sequence, and the frequency difference between the reference oscillators.

In order to obtain the origin and time marks, a 7-pulse pulse block is inserted into the device. The video pulse at the output of the sync pulse block 7 is output at the moment of coincidence of the states of the generators 3 and 6 of the pseudo-random sequences that are executed on the shift register.

The period of the following video pulses is T N / F,

where L is the length of the sequence;

F is the difference between the frequencies of the voltages at the outputs of the generators 1 and 5.

It follows from the formula that the range of time delay can be made as large as possible by reducing the frequency difference between the reference and control oscillators, i.e., it can significantly exceed the period of the reference sinusoidal signal and the range of values of the measured impulse response.

The device provides automatic measurement of the impulse characteristics of an arbitrary shape, and not just exponentially decreasing. The transition characteristic h (t) can be calculated from the measurable values of the impulse response g (t) using the well-known formula

/ g (O-lg (Q} d &.

Claims (2)

1. USSR Author's Certificate No. 501366, cl. G 01 R 29/02, 1975. 2. USSR author's certificate number 442437, cl. G 01 R 23/02, 1972 (prototype).