SU1129547A1 - Non-linear distortion meter - Google Patents

Abstract

MEASURING NONLINEAR DISTRIBUTIONS, containing a sinusoidal signal generator and the first voltage multiplier, which is different from the fact that, in order to increase the measurement speed, the phase shifter, the first and second phase splitters, the second voltage multiplier, the difference block, the low-pass filter, high-pass filter, quadratic detector and voltage ratio measurement unit, the first input of which is connected - Through the low-pass filter to the output of the difference block, the second input - with the output of the quadratic detector, i Which through a high-pass filter is connected to the output of the difference unit, the first input of which is connected to the output of the first voltage multiplier, the second input - to the output of the second voltage multiplier, while the first input of the first voltage multiplier is connected to the first output of the first phase-alternator, the input the first voltage multiplier is connected to the second output of the second phase splitter, the first output of which is connected to the first input of the second voltage multiplier, the second input of which is connected to the second fazorasschepitel output of the first, whose input is analyzed by a nonlinear element connected to the output sinusoidal signal generator which, via a phase shifter coupled to the input of the second 2 fazorasschepitel. R

Description

The invention relates to electrical measurements and can be used to measure non-linear distortions that occur when a sinusoidal signal passes through a non-nickel element, such as a low-frequency amplifier. A device for measuring nonlinear distortions is known, comprising an indicator, a high-harmonic filter connected in series with a calibrated amplifier, as well as two detectors and a switch connected to their outputs; one of the detectors is connected to the output of the calibrated amplifier, and the other in parallel with the circuit of the series-connected high-pass filter, the calibrated amplifier, and one of the detectors, the switch output is connected to the ij indicator. A disadvantage of the known device is the difficulty of tuning its | to another frequency, since the high-pass filter contained in its composition in order to obtain a good measurement accuracy is performed by a multi-link and therefore difficult to adjust. The closest to the present invention is a device for measuring non-linear distortion, which contains a sinusoidal signal generator and a voltage multiplier, the first input of which is connected through a test nonlinear element to the output of a sinusoidal signal generator. The second input of the sinusoidal signal is also connected to the output of the sinusoidal signal generator. the formation of the reference voltage, consisting of a series-connected frequency multiplier n times and frequency converter 2 The disadvantage of this device It is poor in performance, since to determine the harmonic ratio of a distorted signal ... 4Un, it is required to make n independent measurements of the levels of individual harmonics and perform mathematical processing in accordance with formula (1). The purpose of the invention is to increase the measurement speed. The goal is achieved by introducing a phase shifter, a first and second phase splitters, a second voltage multiplier, a difference block, a low pass filter, a high pass filter, a quadratic detector, and a ratio measuring unit in the nonlinear distortion meter that contains a sinusoidal signal generator and the first voltage multiplier. voltage, the first input of which is connected through a low-pass filter to the output of the difference block, the second input from the output of a quadratic detector, the input to which through a high-pass filter connected to the output of the difference unit, the first input of which is connected to the output of the first multiplier of the couplers, the second input - with the output of the second voltage multiplier, while the first input of the first voltage multiplier is connected to the first output of the first phase splitter, the second input of the first voltage multiplier is connected to the second output of the second phase splitter, the first output of which is connected to the first input of the second voltage multiplier, the second input of which is connected to the second output of the first phase splitter, whose input th analyzed via a nonlinear element connected to the output sinusoidal signal generator which, via a phase shifter is also connected to an input of the second fazorasschepitel. The drawing shows a functional diagram of the meter nonlinear distortion. The meter contains a sinusoidal signal generator 1 connected through the nonlinear element 2 under investigation to the first phase splitter 3 and through the phase shifter 4 to the second phase splitter 5. The first output of the first phase splitter 3 is connected to the first input of the first voltage multiplier 6, the output of which is connected to the first input of the difference unit 7 . The first output of the second phase splitter 5 is connected to the first input of the second voltage multiplier 8, the output of which is connected to the second input of the difference unit 7. The second output of the first phase splitter 3 is connected to the second input of the second multiplier 8 voltages, and the second output of the second phase splitter 5 is connected to the second input of the first multiplier voltage b. The output of the difference block 7 is connected via a low-pass filter 9 to the first input of the voltage ratio measuring unit 10, the second input of which is also connected to the output of the difference block 7 through a high-pass filter 11 and a quadratic detector 12. The nonlinear distortion meter operates as follows. The sinusoidal signal from the generator 1 of the sinusoidal signal passes through the nonlinear element 2 under study and is fed to the first phase coupler 3, which has two outputs. The phase difference of the voltages taken from both outputs in a wide frequency range is equal to 90 °. From the first output, conventionally indicated by the index 0 °, the signal arrives at

the first multiplier 6. The second input of the first multiplier 6 receives a signal from the output of the second phase splitter 5, conventionally indicated by the index 90 °. Generator 1 has a sinusoidal signal, also through phase shifter 4, which rotates the phase 90 °, to the input of the second phase splitter 5, from the output O of which the signal goes to the first input of the second multiplier 8, to the second input of which a signal comes from the output 90 ° of the first phase splitter 3. The output signals of the first and second multipliers are subtracted in difference block 7. The output signal of the difference block 7 contains a constant and variable components. The constant component is selected by the lowpass filter 9, and the variable component. - 11 high-pass filter. The variable component is then detected by a quadratic detector 12. The voltage ratio measurement unit 10 determines the ratio of the root-mean-square value of the variable. component to a constant, which gives the value of the nonlinear distortion coefficient. For the correct operation of the nonlinear distortion meter, it is necessary that the phase shift in the element under study be close to zero. Suppose the voltage at the output of the generator 1 has a unit amplitude. Let both phase splitters be identical and have a close phase shift. Denote the phase shift in the first phase splitter 3 at the output O through L, the deviation of the phase shift between the signals from different outputs from 90 p. (The same values in the phase splitter 5 are denoted by p and d, respectively. Consider the meter's work on the first harmonic distorted Signal: The first multiplier 6 receives two signals;

with the release of the first phase splitter 3

and, A, 5in (wl + “.) from the 90 ° exit of the second phase split.

U7 etnlutHeo ° p + bj).

I.

At the output of the first multiplier 6

, 5in (ut +, ei.6in ((. (Iwif

+ et + pv & VcosloJ.-pf-bj.

 The second multiplier 8 will also receive two signals:

output 0 ° of the second phase splitter 5,

and b; п иЬ 5490 °),

from exit 90 of the first phase splitter 3

(ult "(, i-qava,) at the output of the second multiplier

ABOUT 1 sinful) ein (hl h 9%,}

ft ,. , p u, V -fi-u,.

At the output of block 7, the difference

B, b:

i) + 4

U, - Ug-U, A Co5loC-f) -A, .p.5, n-.

Similarly for And-and harmonics at the output of block 7 difference

). C05 ili -AP 5; n (n-1) ubd 4 (i. IL Si g, blAl.

The second term is close to zero, therefore in the spectrum of the signal Uj there are all transformed with decreasing frequency in the form (n-1) and harmonics of the original signal. In this case, the first harmonic corresponds to a constant voltage, which makes it possible to filter out the first and highest harmonics of the distorted signal with high-frequency and low-frequency filters using high-pass and low-pass filters, and a split capacitor can be used as a high-pass filter. The voltage ratio measurement unit 10 generates a non-linear coefficient value, distortions in the form

R

UjtUV- 4 "

g

Considering that the amplitude of the first harmonic is greatest, then it introduces the main error in the measurement of the nonlinear distortion due to incomplete suppression of the second term in the expression for U, the amplitude of this term is equal to

. 4, 1

ft ,,

Therefore, the measurement error can be considered equal

S ... 1 g

In this case, the difference a, - ug can be reduced to fractions of a degree, and the measurement error of 8 - to fractions of a percent. The accuracy of the measurement is also affected by the inaccuracy of the phase rotation in the phase shifter; however, this component can be almost completely eliminated by applying automatic phase adjustment. Also introduces an error in the measurement of the nonlinearity of multiplication. However, modern integral multipliers provide 5-11295476

Non-linearity errors are available for measuring the ratio of nap, 1%, measurements without any mathematical definition: the coefficient of linear calibration and tuning of the meter, signal distortion is produced by what and one way of increasing the speed is achieved immediately.

which processing, preliminary

Claims (1)

NON-LINEAR DISTORTION METER, containing a sinusoidal signal generator and a first voltage multiplier, characterized in that, in order to increase the measurement performance, a phase shifter, first and second phase splitters, a second voltage multiplier, a difference block, a low-pass filter, a filter are introduced highpass quadratic detector unit and measuring the ratio of voltages, the first input of which is connected 'Thérèse filter lower frequencies with _n output the difference block, the second input - to the output of the quadratic detector input cat Or through a high-pass filter, it is connected to the output of the difference block, the first input of which is connected to the output of the first voltage multiplier, the second input is connected to the output of the second voltage multiplier, while the first input of the first voltage multiplier is connected to the first output of the first phaeo splitter, and the second input of the first voltage multiplier connected to the second output of the second phaeo splitter, the first output of which is connected to the first input of the second voltage multiplier, the second input of which is connected to the second output of the first faeorasschepitelya, G. whose input is analyzed by non-linear element connected to the output ζ sinusoidal signal generator which, via a phase shifter coupled to the input of the second 2 faeorasschepitelya.