SU892352A1 - Device for measuring linear four terminal network phase frequency characteristics - Google Patents

Description

() DEVICE FOR MEASURING PHASE FREQUENCY

CHARACTERISTICS OF THE LINEAR FOUR-FLAT

one

The invention relates to a radio measuring technique and can be used for continuous automatic monitoring of the phase-frequency characteristic of a linear quadrupole.

A device for measuring the phase-frequency characteristic (PFC) of a quadrupole is known, comprising a generator with a sweeping frequency, a quadrupole under study, two mixers, a delay line with a linear frequency response, a phase-sensitive device connected to an oscilloscope D.

The drawback of the device is the possibility of measuring the phase response of a quadrupole only when there is no useful signal at its input, which increases the measurement time due to the need to disconnect the test quadrupole from the transmission line and connect the phase measurement device to it.

The closest technical solution to the present invention is a device for measuring the phase-frequency characteristic of a quadrupole, which contains a oscillating frequency generator, the output of which is connected to one of the inputs of the first and second mixers, a fixed frequency generator connected to another input of the first mixer, the following four-terminal, output which through the first switch is connected to another input of the second mixer, a limiter, two phase to voltage converters, an oscilloscope 2.

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A disadvantage of the known device is the impossibility of measuring the phase response while simultaneously having a useful signal at the input of a quadrupole. Therefore, when measuring the phase response,

20 additional time required to disconnect the studied quadrupole from the line in front of it and connect it to the phase response meter. The purpose of the invention is to reduce the measurement time by measuring the phase-frequency characteristic of a quadrupole when passing through its useful signal. This goal is achieved by the fact that in the device for measuring the phase-frequency characteristic of a linear quadrupole containing a fixed-frequency generator connected to the first input of the mixer, the output of which is connected to the input of the linear four-terminal network being studied, connection, the low-frequency output of which through the limiter is connected to the first input of the phase-frequency detector, the second input of which is connected n to a fixed frequency generator, output to a frequency response meter, the output of which is connected to the second input of the mixer and the compensation input of the autocompensator, whose output is the output of the device. The drawing shows a block diagram of the proposed device. The device for measuring the phase-frequency characteristic of a linear quadrupole comprises a fixed frequency generator 1, a mixer 2, a quadrupole 3 under study, an autocompensator k with negative correlation feedback, made, for example, in the form of a mixer 5 mixer. 6, the integrator 7 and the mixer 8. A low-frequency output by the auto pensator k through the limiter 9 is connected to one of the inputs of the phase detector 10, the other input of which is connected to the generator 1, the output of the phase detector 10 is connected to a frequency response meter 11. The device works as follows. The frequency modulated signal from the output of the frequency response meter 11 is fed through two channels; to the quadrupole 3 input after a pre-shift in frequency and to the compensation input of the autocompensator A. The output of the quadrupole will be the resulting signal, which is an additive mixture of the measuring frequency-modulated signal and the useful signal that goes to the autocompensator input A. As a result, the autocompensator channels k of two correlated frequency-modulated signals varying their frequency synchronously; the measuring signal is subjected to coherent compensation, which is matched 7 separating sinusoidal signal of the difference frequency equal to oscillator frequency 1. When scanning a measuring signal in a band equal to the quadripole band under study 3. the signal at the output of the quadrupole 3 at each point of the passband receives the corresponding phase shift determined by the type of phase characteristics of the quadrupole 3. As a result, during the passage of the measuring signal from one edge of the band to the other phase of the sinusoidal signal at the output of the integrator 7 Changes in accordance with the law determined by the phase-frequency i characteristic of a quadrupole 3. In order to determine the law of change of the phase of the signal at the output of the integrator 7, it will move the limiter 9 to one of the inputs of the phase detector 10, to the other input of which signal from the generator output 1. At the output of the phase detector 10 there will be a voltage, the law of changing the level of which, as a function of the current frequency of the measuring signal, carries information about the shape of the phase-frequency characteristic of the quadrupole 3. For If the law of variation of the voltage level at the output of the phase detector 10 corresponds to the law of variation of the frequency of the measuring signal at the input of the quadrupole 3, the voltage of the output of the phase detector 10 is fed to the input of the DC amplifier of the frequency characteristic meter 11. On the screen of the frequency characteristic meter 11, a curve is displayed that replicates the phase-frequency characteristic of the quadrupole 3 under study. To more accurately measure the phase-frequency characteristic of the linear quadrupole, the ratio between the amplitudes of the useful and measurement signals should be selected from the condition. T: 71 | «1Г7- |, where A is the amplitude of the useful signal at the autocompensator output;

Claims (2)

Claim A device for measuring the phase-frequency characteristics of a linear four-terminal network containing a fixed-frequency generator connected to the first input of the mixer, the output of which is connected to the input of the test output of which is connected to the second input of the mixer and the compensation input of the auto-compensator, the output of which is the output of the device. ²⁰ Sources of information taken into account in the examination 1. USSR Copyright Certificate ’No. 121155, cl. G 01 R 27/28, 1958. 2, Copyright Certificate of the USSR ”No. 374551, cl. G 01 R 27/28, 1971. ВНИИПИ Order 11244/67 Circulation 735 Subscription Branch of PPP Patent, Uzhhorod, st. Project, 4