SU1187096A1 - Apparatus for measuring non-linear distortions - Google Patents

Abstract

A DEVICE FOR MEASURING NONLINEAR DISTRICTS, containing a double T-shaped bridge, a converter and an indicator, characterized in that, in order to improve the measurement accuracy, two frequency meters, a decoder, a local oscillator, a selective filter, a switch, a block of quadrators, a weighting adder, are entered into it, a root extraction unit, a divider and a blender, the first input of which is connected through the double T-shaped bridge to the input of the device and to the inputs of the first frequency meter and converter, and the second to the output of the local oscillator and the second h input A meter that is connected to the first input of the decoder, the second input of which is connected to the output of the first frequency meter, to the second input of the double T-bridge and the input of the local oscillator, and the output to the control input of the switch, the outputs of which are connected to the corresponding quad the inputs of the weighing summer S, the mixer output through a selective filter is connected to the switch signal input, and the output of the weighing accumulator is connected through the root extraction unit to the first input of the splitter, the second the input of which is connected to the output of the converter, and the output t is connected to the input of the indicator. 00 "-a about 3

Description

1 The invention relates to radio measurements, in particular, devices for measuring small non-linear distortions. The aim of the invention is to improve the accuracy of measurements by eliminating the additive component of the measurement error of € 1. The drawing shows a structural diagram of the proposed device (for the case of measuring K by five harmonics). The device contains a 2T bridge 1, a mixer 2, a selective filter 3, a switch 4, a first frequency meter 5, a converter 6, an oscillator 7, a decoder 8, a second frequency meter 9., a block of 10 quadrants, a weighing adder 11, a divider 13 and indicator 14. The device input is connected via 2T-bridge 1 to the first input of mixer 2, the output of which is connected to the signal input of switch 4 via selective filter 3, the device input is also connected to the inputs of the first frequency meter 5 and converter 6, the output of the first frequency meter is connected to second Valid y 2T-mos and that the local oscillator 7 and a decoder 8 WMOs rows, a second input coupled to an output of the second frequency counter 9, and the output control unit - to the control input of the switch kitsim. The output of the heterodyne is connected to the inputs of the mixer and the second frequency meter. The switch outputs are located through quadrants placed in a block of 10 quadrants connected to the corresponding inputs of the cjnM weighing device 11, the output of which is connected to the first input of the divider 13 via the extraction unit 12, the second input of which is connected to the output of the converter, and the output as follows. The first frequency meter 5 measures the frequency of the input signal and its output signal, which is the digital code of this frequency, is controlled by switching the matrix sets of 2T-bridge 1 elements (resistor and capacitors), which ensures that the bridge is tuned to the quasi-resonance frequency and, thus , suppression of the first harmonic of the input signal 6. 2. la. The same code controls the frequency range in which the local oscillator 7 is tuned. The highest harmonics of the signal, carrying information about the harmonics of the input signal, are selected using mixer 2 and the selective filter 3. So, if the center frequency of the passband filter, the signal at the output of filter 3 appears if fc - fr .f where fp is the output frequency of the 2T-bridge 1; F. - instantaneous frequency of the output signal of the local oscillator 1. Thus, in order to select, for example, from the 2nd to the 5th harmonic of the input signal, it is sufficient that the tuning range of the local oscillator 7 is within 2f - f; (2) H 2f o - f p; fr.B 5fo - f, p) (3) where f. jj frequency of the first harmonic of the input signal. Since signals with levels proportional to the levels of higher harmonics at the output of 2T-bridge 1, are not present at the output of the selective filter, but appear at times when n fo - f2 f (p, (4) where 3, ... j then, for determining the sum of quadratures of higher harmonics 2 Vi l / j -... (5), a circuit consisting of switch 4, a block of 10 quadrants and a weighting adder 11 is applicable. At times, when the frequency of the output signal the heterodyne 7 fj-, measured by the second frequency meter 9, in accordance with the condition fr p. fo - f (6) the decoder 8 carries a command to the switch The torus 4 is connected to the output of the filter 3 of the corresponding quadr. Thus, the outputs of the block of 10 quadrants sequentially appear signals that are proportional to the squares of the second, third, etc. harmonics of the output signal of the 2T bridge 1. The harmonic ratio of the input signal is determined as .

4vbv ... 4

Lg

 - 1 I.

,

The voltages at the outputs of the squares are

v, "K (Vex.

(8) VK (Ve ,, f.K (K; .v, i%

where K is the conversion factor

quad 10.

Kj, ..., KS are the transfer coefficients of the 2Т-bridge 1 according to the corresponding harmonics;

h.) voltage harmonics

input sggsha. As seemingly from expressions (7) and (8) to determine the root expression of the numerator of the alpha number (7), not 11870964

it is necessary to provide transfer coefficients before summing up accordingly

 5 CJK-K

(9)

(

sk-K,

After summing up in a device with payload coefficients defined by expression (9), the output signal level at the output of block 12 is numerically equal to the value of the numerator of expression (7) „

The value of voltage, respectively. The 1An enamenter of this expression is obtained using the converter 6. The output voltage of the divider 13, equal to the value of the harmonic coefficient, is displayed on the indicator 14.

Claims (2)

DEVICE FOR MEASURING NONLINEAR DISTORTIONS, containing a double T-shaped bridge, a converter and an indicator, characterized in that, in order to increase the accuracy of measurement, two frequency meters, a decoder, a local oscillator, a selective filter, a switch, a block of quadrators, a weighing adder, a block are introduced root extractor, divider and mixer, the first input of which through a double T-shaped bridge is connected to the input of the device and to the inputs of the first frequency meter and converter, and the second to the output of the local oscillator and the input of the second frequency meter, the path of which is connected to the first input of the decoder, the second input of which is connected to the output of the first frequency meter, to the second input of the double T-shaped bridge and the input of the local oscillator, and the output to the control input of the switch, the outputs of which are connected through the block of squares to the corresponding inputs of the weighting adder, the output of the mixer through the selective filter is connected to the signal input of the switch, and the output of the weighing adder is connected through the block extracting the root to the first input of the divider, the second input of which is connected with the converter output, and the output with the indicator input. 2.