SU1730570A2 - Spectral analysis method - Google Patents

Abstract

The invention relates to a measurement technique and can be used to analyze broadband random signals containing regular components. The purpose of the invention is to increase the resolution by detecting low-level signal components. To do this, identify the regular components of the signal and refine the levels of each regular component by successive suppression of the selected harmonic components of the signal, while consistently suppressing all previously detected harmonic components and determining the low-level harmonic components by amplifying , filtering and subsequent refinement of the levels of each harmonic component by their successive suppression. This method is implemented by a spectrum analyzer in a.s. 1322171, in which the block of controlled narrow-band filters 24, the third and fourth adders 25 and 26, the block 27 of harmonic signal generators, the key block 28, the amplifier 29, the fourth key 30 were additionally introduced.

Description

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The invention relates to a measurement technique and can be used to analyze the spectra of wideband random signals containing regular harmonic components.

The aim of the invention is to improve the measurement accuracy.

FIG. 1 shows a functional diagram of a spectrum analyzer implementing the method; in fig. 2 - spectrograms explaining the operation of the analyzer.

The analyzer contains a controlled narrow-band filter 1, an inverter 2, the first adder 3, parallel analysis channels, each of which consists of a band-pass filter 4, a dispersion meter 5, a switch 6, an analog-to-digital converter (ADC) 7, the first key 8, the first block

memory 9, the first converter 10 code-time interval, the second adder 11, the television tube 12, the second converter 13 code-time interval, the second key 14, the generator 15 harmonic signals, the third key 16, the converter 17 frequency-code, comparison circuit 18 codes, counter 19, tag generation unit 20, second memory block 21, calculator 22, symbol generation unit 23, block N of controlled narrow-band filters 24.1-24.N, third and fourth adders 25, 26, generator block 27.1-27. N, block N of keys 28.1-28.N, amplifier 29, fourth key 30. Input control The mobile narrowband filter 1 is the input to the spectrum analyzer and is connected in parallel with the inputs of the controlled narrowband filters 24.1-24.N,

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the moves of which are connected to the inputs of the third adder 25, and its output through the fourth key 30 is connected to the first input of the fourth adder 26, to the second input of which the output of the controlled narrowband filter 1 is connected. The output of the fourth totalizer 26 through the inverter 2 is connected to the first input of the first adder 3 the second input of which is connected to the output of the analyzer, and the output to an amplifier 29, with parallel analysis channels consisting of a band-pass filter 4, a dispersion meter 5, the outputs of which are connected to the inputs of the switch 6. The output through the A / D converter 7 is connected to the second key 14, the second code-time interval 13, the color television tube modulator and the inputs of the first memory block 9 through the first key 8 via serially connected signals. The address inputs of the first memory block 9 are connected to the output of the counter 19 and the control input of the switch 6, the output of the first memory block 9 is connected to the input of the first converter 10 code-time interval, the output of which is connected to the first input of the second adder 11, the output connected to one of the color te modulators tube 12, and the second input to the output of the symbol generation unit 23, the input of which is connected to the input of the calculator 22. The third input of the adder 11 is connected via a tag forming unit 20 to the output of the code comparison circuit 18, the first input of which is connected to the output of the counter 19, the second input- with the output of the frequency-code converter 17 and one of the inputs of the calculator 22, the other inputs of which are connected to the output of the ADC 7, the output of the first memory block 9 and the output of the second memory block 21. The output of the frequency-code converter 17 through the key 16 and through the block of N keys 2 8.1-28.N is connected to generator 15 and block N of generators 27, respectively. In addition, the output of the generator 15 is connected to the control input of the narrow-band filter 1, and the outputs of each of the N generators 27 are connected to the control inputs of the corresponding filters of the N filter 24 block.

Spectrum analyzer works as follows.

The input wideband signal containing harmonic components is fed to the input of the narrowband controlled filter 1, to the inputs of the narrowband filters of the block of N filters 24.1-24N and to the second input of the first adder 3. Initially, the fourth key 30 is open and the tuning frequency of the narrowband filter 1 is outside the frequency range of the spectrum analyzer, i.e. fen tn, where tone is the initial tuning frequency of narrowband filter 1, and fH is the lower operating frequency of the analyzer. In this case

5, there is no signal at the output of the controlled filter 1, and the entire input signal passes through its second input to the output of the first adder 3 without change, the spectrum of which corresponds to FIG. 2, a. Broadband

0, the signal amplified by amplifier 29 to a level that ensures the normal operation of parallel measurement channels is divided by band-pass filters A into a number of narrow-band signals fed to

5 inputs of dispersion measurement unit 5. From the output of the latter, signals in the form of DC voltages, proportional to the dispersions of narrowband signals, are fed to the corresponding inputs of switch 6. From

0 output of the switch 6 signals are fed to the input of the ADC 7, where the signal is converted from analog to digital form. From the output of the A / D converter 7, the signal is digitally supplied through the first key 8 closed in the initial state to the first memory block 9, while the keys 14 and 16 are open and the first memory block 9 and the switch 6 are controlled from the output of the number 19 counter. channel. From the exit

0 of the first memory block 9, the signal is fed through the first converter 10, the code-time interval and the adder 11 to the color television tube modulator 12. When

5, the screen of the television tube 12 highlights the results of parallel spectral analysis in the form of luminous red columns in the number of parallel channels whose levels correspond to the dispersions of signals in the corresponding frequency bands. Thus, at the end of the time of spectral analysis, the results of parallel spectral analysis are found in the first block of memory 9 and at the same time these results are displayed on the screen of the television tube 12. Then the key 8 opens, and the key 14 closes, from the harmonic signal generator 15 The variable frequency signal is fed to the control input of the controlled narrowband filter 1 and tunes it in frequency. The frequency of the harmonic signal is then changed by the operator from fH

5 to TV, where fH, fe are the lower and upper limits of the frequency range of the spectrum analyzer, respectively. From the output of the controlled narrow-band filter 1, the signal through the fourth adder 26 and the inverter 2 is fed to the first input of the adder 3, to the second input

which results in a measured wideband signal. As a result of the antiphase summing of the narrowband and wideband signals, a difference signal appears at the output of the adder 3, and at the tuning frequency of the controlled narrowband filter 1, the signals are fully subtracted, since the gain of the circuit: controlled narrowband filter 1 adder 26. inverter 2 is equal to one, and the total phase shift of the signal is 180 °. In the process of tuning the controlled narrowband filter 1, the tuning frequency is smoothly scanned and the frequencies of the analyzed broadband signal are sequentially suppressed. From the output of the first adder 3, the broadband signal is fed to parallel analysis channels. From the output of the dispersion meter 5, the signals through the switch 6 are fed to the input of the ADC 7, from the output of which the signal is digitally transmitted through the closed third key 14 to the entrance of the second converter 13 code-time interval and then to the modulator of the television tube 12. During the frequency scanning the settings of the controlled narrow-band filter 1 when it coincides with the frequency of the harmonic component, the latter is completely suppressed, which is reflected on the screen display of the television tube 12. At this moment the operator stops The frequency tuning of the generator 15 and closes the second key 16. The harmonic signal from the output of the generator 15 through the closed second key 16 is fed to the input of the converter 17 frequency-code, from the output of which the signal in digital form goes to the first input of the code comparison circuit 18 and to the second the input of the computing unit 22. The second input of the comparison circuit 18 receives a signal in digital form from the second output of the counter 19 of the channel number. When the codes at the first and second inputs of the code comparison circuit 18 coincide, a signal appears at its output, which is fed to the input of the tagging unit 20, from which the signal goes through the adder 11 to the modulator of the television tube 12. At the appropriate place of the raster an indicator appears indicating the position on the frequency axis of the tuning frequency of the controlled narrow-band filter 1. At the same time, the first, third and fourth inputs of the computing unit 22 receive signals respectively the outputs of the second memory block 21, the first memory block 9, and the ADC 7. The second memory block 21 stores information about the amplitude-frequency characteristics of the analyzing filters and the program of calculations. The value of the frequency of the harmonic signal arriving at the second input of the computing unit 22 is estimated

the true value of the amplitude of the harmonic component. From the output of the computing unit 22, the signal characterizing the amplitude value of the harmonic signal at the i-th frequency is fed to the input of the unit 23 of the form of symbols. From the output of this block, a signal carrying information about the level of the harmonic component, formed to display on the screen an indicator of a color television tube 12 in the form of an inscription in

5 at the appropriate place of the raster, is fed through the adder 11 to the modulator of the television tube 12. This will highlight the level of the harmonic component. After that, the operator opens the second key 16 and continues the frequency tuning of the harmonic oscillator 15, thus terminating the calculations in the computing unit 22 and the inscription disappears. Managed narrowband filter 1 when arriving at

5, its variable frequency harmonic control input changes the tuning frequency accordingly, and the process of determining the harmonic components in the signal under study continues similarly to that specified. This completes the first stage of the spectrum analyzer. As a result, all high-level components are detected on it (Fig. 2a) and their amplitudes are calculated taking into account the mutual

5 influenced. However, due to the non-ideal characteristics of the filter, the resulting spectrum will look like that shown in FIG. 2, and the dashed line, and therefore the parameters of the low-level components of the signal remain undefined, since they are masked by high-level components. The exact amplitude values of the high-level components are calculated taking into account the fact that the low-level components 5 introduce a slight error. The distinctive operation of the claimed method is the simultaneous suppression of all previously computed high-level components and the subsequent amplification of the signal

0 to the standard level, the possibility of which is ensured by the absence of high-level components, provides the spectral characteristic shown in fig. 2.6 dashed line. Wire analogy to the first stage — specification of the amplitudes of the low-level signal components by their successive suppression; the parameters of the low-level components are obtained with an accuracy comparable to the accuracy of the &

Claims (1)

nor the high level components. For this, in the second stage, the fourth key 30 is closed. The input wideband signal is fed to the input of the controlled narrowband filter 1, to the inputs of the controlled narrow-band filters of the block of N filters 24.1-24.N and to the second input of the first adder 3. Initial tuning frequency a controlled narrow band filter; 1 g of filters of the block 24 is outside the frequency range of the spectrum analyzer. The lock key 28.1, using the generator 27.1, performs the adjustment of the narrowband controlled filter 24.1 in the same way as the adjustment of the narrowband controlled filter 1 at the first stage until the first high-level component of the signal disappears on the screen. After that, the key 28.2 is closed and the filter 24.2 is similarly adjusted until the second high level component disappears on the screen. This is continued until all high-level components are suppressed. As a result, a signal having the spectrum shown in FIG. 2.6. Further work of the analyzer to determine and refine the low-level harmonic components is carried out similarly to the work at the first stage in determining the parameters of the high-level components. The method of spectral analysis of a signal, which consists in detecting the regular components of a signal by filtering the latter over narrowband channels and then further refining the levels of each regular component by successively suppressing the selected harmonic components of the signal, characterized in that measurements by detecting low-level components, simultaneously suppress all previously identified harmonic components and determine low-level components Uteem amplifying and filtering the resulting signal by N narrowband channels and further refinement of each low-level component by suppressing their sequential. 2 5 5 si