SU1166004A1 - Analyser of complex spectrum of periodic voltage - Google Patents

Abstract

ANALYZER OF COMPLEX SPECTRUM OF PERIODIC VOLTAGE, containing an input unit whose output is connected to the amplifier input, and the input is connected to the input bus, a synchronous detector, the output of which is connected to the indicator input, and a voltage driver, the first output of which is connected to the first input of the synchronous detector, and the input is with a reference voltage bus, characterized in that, in order to increase accuracy and expand functionality, a digital-to-analog converter programmed into it is introduced into it a block and an address driver, the signal input and the output of a digital-to-analog converter are connected respectively to the output of the amplifier and to the second input of the synchronous detector, and the control inputs of the digital-analog converter are connected to the code outputs of a programmable permanent storage unit whose address inputs are connected to the code outputs of the programmable constant storage unit whose address inputs are connected to the code outputs of the programmable constant memory block whose address inputs are connected to the code outputs of the driver addresses, the input of which is connected to the second, the output of the reference voltage generator. U {t) / Od 8

Description

Fi.

The invention relates to a measurement technique and can be used in the study of the nonlinearity of various electrical circuits.

The purpose of the invention is to increase the accuracy of the analyzer and expand its functional capabilities.

Figure 1 shows the structural diagram of the analyzer of a complex spectrum of periodic voltages j on n.2 - timing diagrams explaining its operation.

The analyzer contains an input unit 1, an amplifier 2, a digital-to-analog converter 3, successively connected synchronous detector 4 and inikator 5, a reference voltage driver 6, an address driver 7, a programmable constant memory unit 8.20

The first input of the analyzer is the input of the input unit 1, connected in series with amplifier 2.:

The first output of the driver 6 of the reference voltage is connected to the first 25 input of the synchronous detector 4, the signal inputs and the output of the digital-to-analog converter 3 are connected, respectively, to the output of the amplifier 2 and to the second input of the synchronous detector 30, and the control inputs of the digital-to-analog converter 3 are connected to code outputs of a programmable permanent memory block 8, the address inputs of which are connected to the code outputs of the form Tera | , H, 7 addresses, and the input of the last s, o | CInen with the second output of the driver from the reference voltage.

The analyzer works in the following way - 40 times.

The investigated signal U (t) through block 1, amplifier 2 and digital-to-analog converter 3 is fed to the second input of the synchronous detector 4. 45 The reference voltage (t) with the frequency of the first harmonic W of the periodical voltage under study is fed to the input of the former 6 of the reference voltage The output voltage of the pr - 50 is a carbonic reference voltage with the frequency of the spectral component under study and a phase adjustable relative to the input reference signal, which serves to control the synchronous 55 detector 4. The reference voltage former The clock also contains synchronized high-frequency clock pulses, which through its second output are fed to the input of the driver 7 addresses. Under the action of clock pulses, the address driver 7 generates n-bit codes that interrogate the matrix of block 8. In accordance with the recorded program, block 8 generates voltage in the form of digital codes that goes to the control inputs of the n-bit converter 3. Under the action of these codes switches the bits of the bits of the converter 3 in accordance with the program recorded in block 8. The converter 3 in the complex spectrum analyzer is not only linear and highly accurate, an attenuator, but also serves to form a weight multiplication function that allows eliminating the effect of high odd harmonics and increasing the accuracy of measurements.

The output voltage of the converter 3 is:

willow (a, 2Va, 2, ...,),

where is the input voltage; a „- coefficients of binary sequences, taking values either 1 or O, If one or several controls to the inputs of the converter 3 apply a square-shaped voltage with a doubled frequency of the measured spectral component 2 W and a duty cycle

(jf-2ot),

then, together with the synchronous detector 4, we obtain the weighting function shown in FIG. 25. FIG. 2oi is a plot illustrating the moments of the closed state of the keys t, converter 3. For a full-wave synchronous detector, the spectral composition of such a weight function looks like this:

.y (t) rA S cos ko (3in k Wt, T, 3, r

where A a 2 + a2 2 - +, ...,.

Hence, it is obvious that to eliminate the effect of any harmonic k, it suffices to fulfill the condition

cos.

For example, it is necessary to eliminate.: The influence of the third, often most significant, harmonics of the signal under study, then

o6 | - 30.

In this case, the converter 3 performs an attenuator function. Thus, for a twelve-bit digital-to-analog converter, any transmission ratio from 1 to 1: 2048 is provided, and high accuracy, linearity, and stability of transmission coefficient are achieved.

To form a more complicated signal, the key switch mutation of the converter 3. (FIG. 2 c, d, e) using block 8, it is possible to form the desired weight function. Thus, in Fig. 2, c, d, the switching laws of the keys of the converter 3 are shown to form weight functions that are insensitive to the third, fifth and third, fifth, seventh, ninth (3.5 and 3.5.7.9 ) the harmonics of the signal being studied, respectively. As can be seen from Fig. 2e, transducer 3 and block 8 allow an approximation of the sinusoidal weight function to achieve the required accuracy of the analyzer (this weight function, for example, is insensitive to harmonics).

Further, the measurement process of the spectral components of the signal occurs as follows. The frequency of the output signal of the reference voltage generator 6 is set, which is inhibited by the frequency of the spectral component under study. By adjusting the phase, a zero phase shift is established between the input reference voltage (t) and the output voltage of the reference voltage driver 6. The reading on the indicator 5 is taken. Then the phase shift in the driver 6 of the reference voltage is set to 90, and again the indicator is taken on the indicator 5.

Thus, two quadrature components of the studied harmonic are measured, by which its amplitude and phase are determined relative to the first harmonic by the known formulas:

And fuf + uT; F arg tg,

where and and, are the measured values

quadrature components.

The reference voltage driver 6 may be a B11B10 lnn, for example, in the form of a phase locked loop with frequency dividers in the feedback circuit and an adjustable phase.

Thus, the Ultimator analyzer of the complex spectrum of periodic voltages has a high measurement accuracy by eliminating the influence of the odd harmonics of the input signal. In addition, it allows one to investigate signals of various shapes due to the possibility of forming a wide range of functions: transferring 1x to a programmable fixed preset device.

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FIG. 2

Claims (1)

ANALYZER OF AN INTEGRATED PERIODIC VOLTAGE SPECTRUM, comprising an input unit, the output of which is connected to the input of the amplifier, and the input is connected to the input bus, a synchronous detector, the output of which is connected to the indicator input, and a reference voltage generator, the first output of which is connected to the first input of the synchronous detector, and input - with a voltage reference bus, characterized in that, in order to improve accuracy and expand the functionality, a digital-to-analog converter is introduced into it, programmable permanent memory and an address generator, the signal input and output of the digital-to-analog converter are connected respectively to the output of the amplifier and to the second input of the synchronous detector, and the control inputs of the digital-to-analog converter are connected to the code outputs of the programmable read-only memory block, whose address inputs are connected to the code outputs shaper addresses, the input of which is connected to the second output of the shaper reference voltage. SU .. „1166004