SU1368890A1 - Device for determining coherence function - Google Patents

Abstract

The invention relates to the applied analysis of random signals, the analysis of the functioning of various dynamic systems, their testing, diagnostics and the development of technical analysis tools. The purpose of the invention is to increase accuracy. For this, a dividing block 5 is inserted into the device, the inputs of which are connected respectively to the output of memory block 4, in which the Fourier transform results of the autocorrelation function of the intercorrelation function of the input signals being analyzed are stored, and with the output of the discrete Fourier transform block 3 conversion of the mutual correlation function of the autocorrelation function of the input signals. 1 il. (L

Description

fu / w)

The invention relates to the field of applied analysis of random processes and can be used to study a variety of dynamic systems, in the diarrhea of mechanical systems, etc.

The purpose of the invention is to improve the accuracy (in determining the coherence function by reducing the number of arithmetic operations by organizing the calculation using a single discrete Fourier transform at once the product of spectral densities).

The drawing shows a block diagram of the device.

The device comprises a multiplexer 1, a co-rotor meter 2, a discrete Fourier transform unit (DFT) unit 3, a memory unit 4, a division unit 5 and a synchronization unit.

The device works as follows.

To determine the coherence function

At M I Sy (tof / S X SJ, (o1 (1)

It is necessary to determine the following functions | s, | (ul, S (co), S (oi). In the device, the spectral power density of the random signal Zit (t) is determined by the cosine transform of the found correlation function R (in) of the signal Z.

(with)

 five

 L I O

Cos raoi-h.

k (t)

-to; (about

.

(2)

where Q is the signal sample size, h. -c is the correlation window; t, is the sampling period.

The inputs of the device receive samples of the correlation functions K (, K.N, K, (w) of the processes x and y.

Coherence functions (1) are calculated in two steps. At the first stage, the numerator (o) is calculated and stored in memory block 4, in the second stage the denominator 8 (and) x X SJw is calculated by division by block 5.

The signal 7 of the matching unit 6 connects the second information input of the multiplexer 1, sets the correlometer 2 to the calculation mode of the autocorrelation function (ACF), and block 4

902

memory - in recording mode. According to the signal 8 of the block 6, the ACF samples K, „(n) from -N to + N are formed in a time series K (n), arriving at the third input of the sample sequence of the device. The samples K, n (n) go to block 3 of the discrete Fourier transform where the spectral power density is determined in accordance with (2). At the same time, signal 9 in block 3

The DFT of the input sequence R, u (n) is multiplied by the correlation window h.

according to the SR function signal

10, K samples are calculated, and the output of block 3 of the DFT, up to a multiplier, the estimate of the square of the module, i.e.

S, .j (),

(but)

2T

l (a + 1)

S ,, (co) f. (3)

By the addresses generated by the signal 11 of block 6, the samples (3) are recorded in block 4 of the memory in K cells.

5 In the second stage, the signal 7 of the unit 6 connects the first information input of multiplexer 1, sets the correlometer 2 to the calculation mode of the mutual correlation function (ICF)

0 and memory block 4 is in read mode. The signals a K (p) and 1, K, (p), which are counts from -N to + N ACF of the corresponding signals x and y ", are received respectively on

 the first and second inputs of the sequence of samples of the device. Signal 8 of block 5 using a correlometer 2 calculates Q + 1 counts of the CCF Rgi, (n), which are received in block 3 of the DFT, where

0, similarly to the previous one, the estimate of the power spectral density of the signal RgLCn) is calculated by the algorithm (3), and at the output of block 3 the DFT, with accuracy to the multiplier, is formed

5 rating

2

Sn (co)

(CO)

S., (CO),

0

 a (Q + 1)

which arrives at dividing unit 5 at the same time as estimating (3) SR (co) from memory 4 by signals 11 of block 6. As a result, an estimate of the coherence function (1) is formed at the information output of the device

55 years) Thus, in the second stage, the calculation of the coherence function using a single DFT is calculated immediately

product S (u)

S (with).

1368890

Claims (1)

Fourier transform claim, input device; Device for determining reception function and input coherence calculation start, containing a multi-one connected to a typelexer, correlometer, discrete-third and fourth output block of the Fourier transform, memory block, the fifth output of which is ti and the synchronization unit, the first is connected to the address input of the block; the output of which is connected to the input of the conversion; the information input of which is controlled by the writing / reading of the block is connected to the output a discrete memory block, a Fourier transform reception synchronization input, an ohl-correlometer and a control input, so that, for the purpose of a multiplexer, the first information-increasing accuracy, into which the input input is an input of a division unit, the output of which is the first sequence of samples with the information output of the device, the input of the second sequence, the input of the task of the correlator of samples which is the function of which is the second input of the first sequence from the multiplexer information input, correlometer counting, the second output of the discrete transform sample block of which neither Fourier is connected to the first input connected to the multiplexer output, 20 of the division block, the second input of which the second output of the synchronization block is connected to the output of the block the memory is keyed to the clock input of the correlomet- the first output of the synchronization unit of the memory, the output of which is connected to the information input to the synchronization input of the block input of the discrete remote control unit.