SU1383218A1 - Analyzer of complex spectrum of periodic voltages - Google Patents

Abstract

The invention relates to the field of electrical measuring equipment and allows to expand the dynamic range of the analyzer. The device contains an input unit 1, an amplifier 3, a digital-to-analog converter 4, a synchronous detector 5, an indicator. 6, the reference voltage generation unit 7, the address generation unit 8, the persistent storage device 9 and the integrator 14. The introduction of the subtraction unit 2, the address generation unit 11, the persistent storage device 12, the digital-analogue converter 13 and the formation of new functional connections provides automatic compensation of the maximum interfering harmonic of the input periodic voltage. 2 Il. F (L

Description

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The invention relates to electrical measuring equipment, namely to the field of creating complex spectrum analyzers with a wide dynamic range.

The purpose of the invention is to expand the dynamic range of the measurement by automatically compensating for the maximum interfering harmonics of the input periodic voltage.

Fig. 1 shows a functional diagram of the proposed analyzer of a complex spectrum of periodic voltages; Fig. 2 shows voltage plots demonstrating the achievement of a positive effect of the proposed analyzer.

The analyzer of a complex spectrum of periodic voltages contains a series-connected input unit 1, whose input is connected to the input bus, subtraction unit 2, amplifier 3, first digital-to-analog (D / A) converter 4, first synchronous detector 5 and indicator 6, in addition to block 7 forming the reference voltage, the input of which is connected to the bus voltage input voltage, the first output is connected with the control input of the first synchronous detector 5, the second output through the serially connected first block 8 of the formation of addresses and ne The first permanent memory (ROM) 9 is connected to the code inputs of the first DAC 4, the third output is connected to the control input of the second synchronous detector 10 and the fourth output through the serially connected second address generation unit 11 and the second ROM 12 is connected to the code inputs of the second DAC 13 The output of the amplifier 3 is connected through the second synchronous detector 10, the integrator 14 and the second D / A converter 13 connected to the second subtraction unit 2.

The analyzer works as follows.

The input signal U (t) under study is through the input block 1, block 2 subtraction, amplifier 3 and DAC 4 is fed to the input of the first synchronous detector 5. Reference voltage Uon (t) with the frequency of the first harmonic of the investigated periodic voltage U (t) is fed to the input of the unit 7 of the formation of the reference voltage, which produces a rectangular support

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The voltage with the frequency of the spectral component under study and the phase regulated relative to the input reference signal serves to control the first synchronous detector 5. On the second output, the generation unit 7 generates synchronized high-frequency clock pulses that are fed to the input of the address generation unit 8. Under the action of clock pulses, the address shaper 8 generates n-bit codes that interrogate the matrix of block 9. In accordance with the recording program, block 9 generates codes that control the n-bit converter 4. Under the action of these codes, Dov converter 4 in accordance with the recorded in block 9 program. The DAC 4 in the analyzer serves primarily to form the required time multiplication function, which eliminates the influence of the higher odd harmonics of the input voltage. For example, a step approximation of the harmonic weight function is synthesized by changing the coefficient of transfer of block 4 according to a harmonic law during the half period of the harmonic under study and subsequent synchronous detection in block 5.

The formation unit 7 also generates a rectangular reference voltage for controlling the second synchronous detector 10 and another sequence of synchronized high-frequency clock pulses, which are fed through the fourth output to the input of the address generator 11, As a result, the latter generates a code for polling the matrix of ROM 12, which, in accordance with the recorded program generates codes that control the second DAC 13.

The process of measuring the spectral components is as follows. Sets the frequency of the output signal of the driver 7 to the first output, equal to the frequency of the first harmonic of the input signal. By a smooth change in the phase of the Lore voltage, the zero indication of indicator 6 is set to possibly bo- more sensitive scale. This setting indicates that the voltage of the first harmonic of the input signal, the voltage of the reference signal

and the voltage of the reference oscillation is strictly square, i.e. shifted in phase by 90. Then the phase of the reference voltage is changed exactly by 90 ° and the indicator 6 is read, which corresponds to the module of the first harmonic of the signal under study. Its phase shift relative to the reference voltage corresponds to the reading of the graduated phase shifter of block 7. If the phase shifter is not graduated, then setting the zero or previously known phase between the input reference voltage and the voltage of the control detector 5, determine the phase of the first harmonic of the input signal using formula results

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1 - with where Ug and Uc - measurement results

quadrature harmonic components.

. A rectangular reference voltage with a frequency equal to the frequency that is highest in terms of the highest harmonic of the periodic signal under study, for example, the second and the third (information about the number of the maximum component is usually a priori), is fed through the third output of block 7 to the control input of the second synchronous detector 10 As a result, a voltage appears at its output, the constant component of which is proportional to the amplitude and cosine of the phase of the component to be suppressed. After low-pass filtering and DC amplification in block 14, this voltage is applied to the reference input of the DAC 13. High-frequency clock pulses through the fourth output of block 7 and the address driver 11 are fed to the inputs of ROM 12 as digital polling codes. The matrix of block 12 contains harmonic function codes, so the output of converter 13 is a quasi-harmonic signal with a frequency of the supplied component, which is fed to the second input of block 1 and subtracted from the input signal under study. Closed circuit auto-regulation. ting, formed by blocks 2-3-1014-13t2, in a stationary mode produces a compensating signal at the output of the converter 13 with such amplitude M 1 that

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where Mn and if is the amplitude and phase of the pressure component.

Thus, at the output of the amplifier 3, the voltage of the suppressed higher harmonic is the smaller, the closer (j to zero, (180 °). At H, -90 (270 °), the phase of the compensating voltage produced changes by 90 °.

However, the maximum positive effect in the expansion of the dynamic range is achieved by analyzing the higher harmonic components, since the amplitude of the first, interfering in this case, harmonics of real periodic signals, as a rule, is much greater than the amplitudes of their higher harmonics, and the first harmonic of the input signal under investigation is suppressed completely because the phase shift 1-cr between the first harmonic U (t) and the reference voltages of the detectors 5 and 10 is set by means of the indicator 6 to exactly zero.

So, at the output of amplifier 3, the signal under study appears without the first, maximum interfering harmonic. Consequently, the dynamic range of the analyzer is increased by as many times as the amplitude of the first harmonic is greater than the maximum amplitude of the higher harmonic. The frequency of the output reference signal of the unit 7 controlling the synchronous detector 5 is set equal to the frequency of the spectral component under study. The reading on indicator 6 is taken. Then the phase shift in driver 7 is set to 90, and again the display is taken on indicator 6.

After measuring the two orthogonal components of the harmonic under study, its amplitude and phase are determined relative to the first harmonic by the known formulas

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The voltage plots illustrating the achievement of a positive effect are shown in Fig. 2 (the output voltage of the DAC is shown as a solid line, the dashed line shows a variant of the form of the compensating voltage). Such a voltage allows

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completely eliminate the first harmonic from the input signal and introduce higher harmonics into the input signal, starting only with the eleventh one, i.e. allows to measure the amplitudes and phases of the first ten highest harmonics of the signal under investigation in the maximum dynamic range. To measure a larger number of higher harmonics in an extended dynamic range, it is necessary to complicate the compensating signal.

Thus, the proposed analyzer of a complex spectrum of periodic voltages has an extended dynamic range due to preliminary automatic suppression of the maximum harmonic interference.

Claims (1)

Invention Formula The analyzer of a complex spectrum of periodic voltages, containing an input unit, KOTOpol o input is connected to an input bus, a series-connected amplifier, a first digital-to-analog converter, a first synchronous detector and an indicator, and a reference voltage shaping unit, whose input is connected to the bus input reference voltage.  Hhvl and avriolnve in mgmmpmg UfO Amfdyu nsag / mu epvv CLAIM WKI) Lee / 90UBMRMI wash your tSAlUt}) VNIIPI Order .1290 / 41 Random polygons pr-tie, Uzhgorod, st. Project, 4 g 0 five 0 86 the first output is connected to the control input of the first synchronous detector, and the second output is connected through the serially connected first address generation unit and the first permanent memory device connected to the code inputs of the first digital-to-analog converter, in order to expand the dynamic measurement range , a subtraction unit, a second synchronous detector, a second address generation unit, a second read-only memory, a second digital-analogue converter, and an integrator, with The first input of the subtraction unit is connected to the output of the input unit, and the output is connected to the input of the amplifier, the output of which is sequentially connected to the second synchronous detector, the second integrator and the second digital-to-analog converter connected to the second input of the subtracting unit, the third output of the reference voltage generation unit interface is connected to the control input of the second synchronous detector, and the fourth through the second address generation unit and the second permanent storage device connected in series with the code inputs and second digital to analog converter. F "d / Circulation 772 Subscription