SU389525A1 - ALL-UNION MTYUSH- ':: to:. [~: ~ [[•• :: "_ - Google Patents

Description

ANALOG-DIGITAL SPECTRAL ANALYZER

one

The invention relates to specialized computer equipment for spectral analysis of electrical random signals.

Spectral analysis devices are known to include analog-digital and digital-to-analog converters, a memory, a control unit, a clock, a computing unit, and a plotter.

The disadvantage of such devices is low resolution.

In order to increase the resolution, the proposed analyzer contains a tunable low-pass filter connected to the inverter, the first and second electronic switches connected by the first inputs to the tunable filter, and the second to the inverter. The outputs of the switches are connected respectively to the cervic and second integrators, the inputs of which are connected to the analog computing unit. The control unit is connected to the control inputs of the analog-digital and digital-analog converters, memory, electronic switches and to a plotter connected to a tunable filter.

FIG. 1 shows a block diagram of the proposed device, which contains a multi-limiting analog-to-digital converter (MACP) /, a storage device (memory) 2, a multi-limit digital-analog converter (MCAP) 3, a tunable low-pass filter 4, an inverter 5, electronic switches 6, 7, integrators 8, 9, analog computing unit 10, plotter //, control device 12 and pulse generator 13.

FIG. 2 shows the graphs of the function Fs (b, 1) and f5 (6,) and the impulse function, in accordance with which the electronic keys 6 and 7 are controlled.

FIG. Figure 3 shows the logical structure. control device, which contains a pre-counter 14, a clock counter 15, a cycle counter 16, a pulse counter 17, a coincidence circuit 18, a delay line 19, a pulse distributor 20, an additional digital-to-analog converter 21, and a limit switching circuit 22 ..;

The analyzed electrical - signal - (in particular, the interferrogram signal in the Fourier spectrometer) is fed to the input of the converter. The discrete and quantized signal in binary code is fed to the input of memory 2 of the sequential type. Signal registration ends up filling up the memory.

The device used known algo. rhythm allowing for continuous

Fourier transform and it does not have algorithmic resolution limitations. The multiplication operation by cos "with an accuracy of up to the n / a coefficient n / 4 in the calculating calculator is performed using a tunable low-pass filter 4, an inverter 5 and electronic switches 5 and 7.

In the analysis, information is repeatedly read from memory 2 and fed to the input of converter 3. A continuous signal is fed to the input of filter 4, which filters out all high harmonics, starting from the threefold analysis frequency. Electrical signals from the outputs of the filter 4 and inverter 5 are fed to electronic switches 6, 7. In FIG. Figure 2 shows that using even pulses, the signal is multiplied by (pc (9.0, and using odd pulses) Hia fz (9.0 -C outputs of integrators 5 and 9, signals are taken proportional to So (6) and Ss ( 9) and are fed to the input of the analog computing unit 10, in which the value 5A (9) is determined by solving the following expression:

5l (0) -: 15s (0) C-5DO) 1/2.

A signal proportional to 5A (6) is fed to the input Y of the plotter 11. To the input X of the plotter, a signal proportional to the frequency being analyzed is fed from the control unit 12. An axis (variable resistance) is connected to the axis of the motor moving the stylus pen along the X axis. The filter 4 is modified by changing the control unit 12 to the high-frequency crystal oscillator 13, the signals of which are the basis for the analysis frequency and the frequency of reading information from the memory and commands for switching the limits of the MACP (| When registering) and MCAP (when analyzing).

Preliminary counter 4 lowers the generator frequency to the clock frequency of polling of memory 2. The clock counter 15 from the high-order single output outputs a pulse to the low-pass counting input of the loop counter 16. The memory polling cycle consists of a number of clocks equal to the number of memory bits Memory. The generation of the analysis frequency is as follows.

The state of the cycle counter 16 is entered through the coincidence circuit 18 into the pulse counter 17, to the counting input of which the pre-counter 14 receives pulses with a frequency four times the maximum analysis frequency. If the analysis occurs from the maximum frequency, then the state of the cycle counter is entered into the counter of pulses in the reverse code, i.e. from the inverse outputs. When the impulse counter of pulses is reset from the counter, it goes to the pulse distributor 20 and through the delay line 19 to the Matching circuit 8. The pulse distributor 20 controls the electronic switches 5 and 7.

Circuit 22 of switching the limits of the operation of the converters and 5 consists of triggers (by the number of limits of operation), controlled by the clock counter. Each trigger of the circuit is brought to the zero state by a signal with a subsequent trigger, and the last one is zeroed at the end of the cycle.

The multi-limit operation of the converters / and 3 provides the necessary value of the dynamic range without increasing the word size of the memory.

Considering that a typical interferogram is a function that rapidly decays with a large dynamic range, this

the interferogram recording and reproducing device allows optimal use of the capacity of the serial memory.

In addition to obtaining high resolution, the described detector has an enhanced

noise immunity and smaller errors, since it uses one common high-frequency pulse generator 13 to generate the analysis frequency and the sampling frequency of the memory device.

using digital circuits and the instability of the generator does not affect the quality of the spectral analysis.

An additional advantage of the calculator is that it allows for qualitative (strictly symmetric) interferograms recorded from zero to maximum delay to produce only the cosine Fourier transform, which makes it possible to double the resolution of the calculator with a constant memory capacity.

The advantage of the calculator is also the possibility of using it when registering interferograms using the modulation frequency conversion method, which is used when the modulation frequency region of the signal is shifted to the low frequency region. This method allows you to narrow the region of the noise spectrum, which, in turn, allows

increase the sampling rate and the constant time of the recording path, and therefore, without increasing the memory capacity, increase the resolution and signal-to-noise ratio in the spectrum.

Subject invention

An analog-to-digital spectral analyzer containing an analog-to-digital converter connected to a sequential storage device connected to a digital-analog converter, an inverter, a first and second integrator, an analog quick setting unit, a plotter and a control device connected to a pulse generator, characterized by that, in order to increase the resolution, it contains a tunable low-pass filter connected to the inverter, the first and

the second switches, connected by the first 5 inputs to the tunable filter, and the second switches - to the iiver; switch outputs are connected respectively to the first and second integrators, the outputs of which are connected to an analog computing unit; device-5

1 2 3 5 6 7 8 5 th 11 IZ 6 The control unit is connected to the control inputs of the analog-digital and digital-to-analog converters, memorizing its devices, switches and to the plotter connected to the tunable filter.