SU408226A1 - POWER SPECTRUM ANALYZER - Google Patents

Description

one

The invention relates to specialized computer hardware and can be applied to calculate an estimate of the power spectrum of dynamic products, such as vibrations. It can be used in the study of object B in mechanical engineering, railway transport, engine building, aviation, etc.

A device is known for measuring the peak voltage and frequency of electrical signals and based on the principle of heterodyning of the signal under investigation, followed by the frequency of selecting the difference frequency and determining the magnitude of its separation and temporal position using a measuring device.

The device consists of a connected local oscillator connected to a sweeping frequency generator, the local oscillator output is connected to the mixer input, another input is connected to the output of the input source, to the input of which an electrical signal is received. The signal voltages and the local oscillator are mixed to produce an intermediate frequency signal, which is extracted using an intermediate frequency amplifier (IFF). The output of the amplifier is connected to a rectifier, the signal from which is fed through a peak detector to a measuring device.

The known device is characterized by large errors of the obtained estimates and spectra of real dynamic processes, which are a mixture of deterministic. and

random components, often of a non-stationary nature. For stationary signals, various hardware implementations of time averaging justify themselves. On non-stationary dynamic areas

processes obtain results that have nothing to do with actual effects. The purpose of the invention is to improve the accuracy of determining the power spectrum.

For this, the proposed analyzer contains an additional measuring unit, a delay line and an adder, the first input of which is connected to the output of the first delay line, the input of which is connected to the output of the measuring unit, the second input of the summator

is connected to the output of the additional measuring side, the first input of which is connected to the output of the input source, and the second input to the output of the second delay line, the input of which is connected to the output of the sawtooth generator.

The drawing shows the block diagram of the proposed heterodyne power spectrum analyzer dynamic processes. The device consists of two asynchronously working measuring blocks 1 and 2, united by the input source 3 of the input signal. Each of the cocTOtfT and t cm circuits are 4, local oscillator 5, narrowband filter 6, quad 7, detector 8, low frequency filter 9, delay lines 10 (the second measuring unit has 10 ne delay lines). The block diagram includes an adder 11, which combines the two measuring blocks at the inputs. The local oscillators 4 of the two measuring units are controlled from the sawtooth generator 12, the local oscillator of the second measuring unit being connected to the sawtooth generator 12 via the delay line 10.

The device works as follows.

A CADI measuring unit performs a sequential analysis. The input X (t) from source 3 in mixer 4 is mixed with the signal of the local oscillator 5 and fed to a narrowband filter 6 tuned to an intermediate frequency. Then the signal from the filter is squared using the quad 7, detected by the detector 8, smoothed by the filter 9. The signal from the first measuring unit through the delay line 10 is fed to the first input of the adder 11, and from the second input of the second adder .

At the output of the low-pass filter of each measuring unit of the heterodyne analyzer, an estimate of the current spectrum of the process being studied is obtained.

5I,). | Io-A

where T is the averaging time:

Xi (i) is the process implementation under investigation.

If the process under study is described by a case of a stationary function, then the spectrum estimates, which inhibit this process, can be obtained at any arbitrary time. With an appropriate T, they will not be different -.

However, when the process under study is non-stationary (and the majority of real processes and have some non-stationarity), the result of spectral analysis depends on TO-FO, at which points in time the characteristics were calculated. In order to increase the accuracy of the calculated estimate of the spectrum of the process under investigation, two asynchronous estimates of the current spectrum are obtained, shifted relative to one another by 0.4-0.6 of the control sawtooth period.

& the proposed heterodyne analyzer to simultaneously improve the accuracy of the obtained spectrum estimate uses synchronous summation of responses from two measuring selection systems controlled by time-shifted control sawtooth voltages.

Synchronous summation is accomplished by introducing delay lines between the output of the sawtooth generator and

1 INPUT of the local oscillator of the second measuring unit.

The measure of the correspondence to the obtained hardware estimate of the spectral characteristic φ (, () of the true spectral function -f (w, f) can be expressed as the mean square error of the summary result of the calculations, determined by the formula

g I S (sh. {)

((u, /) - -t -

(2)

yN

N is the number of independent

Where

spectrum estimates;

(", 0 is a squared error

the result of the determination; (oz, t) is the root mean square error of the result of the determination by a conventional heterodyne analyzer. For this case, L 2 and, therefore, the root mean square error of determining the power spectrum compared to the root mean square error of the prototype

will be

a 1 (co, /) 0.76 S (w,) 1. (3)

With a high degree of accuracy in the determination of the spectrum estimate, the proposed analyzer preserves the detail of the spectral characteristics of the process under investigation and successfully solves the problem of finding the hidden periodicities contained in a complex signal.

Subject invention

A power spectrum analyzer containing a sawtooth generator, an input source, the output of which is connected to the first input of the measuring unit, consisting of a chain of serially connected mixer, narrowband filter, quad, detector and low frequency filter, the second input of the mixer, connected to the output of the local oscillator, the input of which is connected to the output of a saw-tooth voltage generator, characterized in that, in order to increase the accuracy of determining the power spectrum, the analyzer contains measuring unit, delay lines and adder, the first input of which is connected to the output of the first delay line, whose input is connected to the output of the measuring unit, the second input of the adder is connected to the output of the additional measuring unit, the first input of which is connected to the output

the input source C 1gl, and the second input - to the output of the second delay line, the input of which is connected to the output of the saw-tooth generator.