SU550649A1 - Device for determining correlation functions - Google Patents

Description

High frequencies 7, 8, multiplying blocks 9, 10, averaging blocks 11, 12, amnlitude detectors 13, 14, subtracting unit 15, adder 16 and recording unit consisting of frequency meter 17, phase meter 18 and amplitude meter 19.

The device works as follows.

Random processes occur at the inputs of mixers 2, 3, which are characterized by a time delay t due to controlled delay line 1. The other inputs of mixers 2, 3 are applied to heterodyne voltages whose frequencies differ by a predetermined value F. At the outputs of the mixers, we have converted random frequencies processes whose spectra are shifted relative to each other by frequency F. With the help of low-frequency filters 5, 6 and high-frequency filters 7, 8, the spectra of these processes are divided into two parts, multiplied in blocks 9, 10, averaged into a block ah 11, 12 and summed up. As a result, the following voltage is formed at the output of the adder 16

oo

f / (/) y / s J GC (f) COS {2itF - 21t / t) df, o

where K is the coefficient of proportionality;

GC (/) is the spectrum of the process under study. After a simple transformation we get

and (t) - Ya + b cos (- arctg where

oo

a JG, (f) cos (2ufT) rff

oo

b (Gc (f) sm (2uHfl /. b

Thus, the amplitude of the harmonic oscillation at the output of the adder 16 is proportional to the envelope of the correlation function, and the phase φ arctg corresponds to the phase of the high-frequency filling of the correlation function.

If the automatic adjustment system of the controlled local oscillator, including the amplitude detectors 13, 14 and the subtraction unit 15, is working properly, the oscillation phase at the output of the adder 16 will be equal to

p 27r (/ r + fp).

where fr is the frequency of the controlled local oscillator, / p is the frequency between the low and high frequency filters.

Thus, measuring the amplitude of the oscillations at the output of the adder 16 determines the ordinate of the correlation function of the process under study, and measuring the phase of this oscillation with the meter 18 and the frequency of the controlled local oscillator with the meter 17 determine the argument of the correlation function

f

t:

27: (L + / p)

Such a measurement increases the accuracy of the estimate of the correlation function, especially for high-frequency random processes.

Claims (2)

1. V.N. Zhovinsky and V.F. Arkhovsky. Correlation devices. M., “Energie, 1975, p. 19, 115. 2. USSR author's certificate No. 206190, M. Kl.2 G 06G 7/19, publ. 1967