SU1700497A1 - Device for measuring amplitude-frequency characteristic of mixer - Google Patents

Abstract

The invention relates to a radio metering technique and can be used to measure the amplitude-frequency characteristics of mixers in the microwave range. The purpose of the invention is to simplify the design. The test mixer 8 receives signals from the generator 1 and the local oscillator 2, the frequency difference of which is constant and equal to the frequency of the generator 7. The introduction of line 5 causes a frequency shift of the signals at the inputs of the phase detector 9. At the same time, a voltage is generated at its output The frequency response of the mixer 8 1 Il.

Description

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The invention relates to a radio metering technique and can be used to measure the amplitude-frequency characteristics of mixers in the microwave range.

The purpose of the invention is to simplify the design.

The drawing shows a structural electrical circuit of the proposed device.

The device for measuring the amplitude-frequency characteristic of the mixer contains (generator 1 with linear frequency modulation, local oscillator 2, mixer 3, phase locked loop 4, delay line 5, block 6 automatic power control, intermediate frequency generator 7, test mixer 8, phase detector 9 and indicator 10.

A device for measuring the amplitude-frequency characteristics of the mixer works as follows.

The test mixer 8 receives signals from generator 1 and local oscillator 2, the frequency difference of which is set by generator 7 and maintained by a constant error signal generated in block 4 when comparing the frequency from the output of mixer 3 and generator 7. The error signal from the output of block 4 is fed to control input the local oscillator 2. In the absence of the generator 1 signal, the frequency of the signals at the inputs of the phase detector 9 is the same. Introducing a delay by switching on line 5 between generator 1 and block 6 under the condition that generator 1 operates in the frequency sweep mode causes a frequency shift of the signals at the inputs of the phase detector 9 equal to rAF

(D where m is the delay value;

A F - oscillator frequency tuning band 1;

t is the time adjustment frequency of the generator 1 in the band L F,

At the output of the phase detector 9, oscillations of frequency F take place, the amplitude of which is equal to

A K (ft) -Uc -Cfd, (2)

where K ((i) is the conversion ratio of the test mixture is 8;

F. I Uc - the amplitude of the signal at the signal input of the mixer 8;

QFD - the transmission coefficient of the phase detector 9.

The signal level of the local oscillator 2 is chosen significantly higher than the level of the input signal, which ensures the independence of the conversion coefficient of the tested mixer 8 from the level of the local oscillator 2.

The level at the signal input of the test mixer 8 is kept constant by block 6. Thus, the information about the amplitude-frequency characteristic of the test mixer 8 lies in the level of oscillations at the output of the phase detector 9 and is determined by the display screen 10.

Thus, the introduction of line 5 allows the formation of frequency-shifted

signal using a single oscillating frequency generator with linear frequency modulation, thereby simplifying the design.

Claims (1)

Invention Formula An apparatus for measuring the amplitude-frequency characteristic of a mixer, comprising a linear frequency modulated oscillator, an automatic power control unit whose output is the first output for connecting the signal input of the tested mixer, a serially connected local oscillator, a mixer and a phase locked loop unit, a serially connected intermediate frequency generator, a phase detector and an indicator; the intermediate frequency generator output, the linear frequency modulated oscillator output is connected to the second mixer input, the phase detector input is the input for connecting the test output of the mixer and the output the heterodyne is the second output for connecting the heterodyne input of the tested mixer, differing in that, in order to simplify the design, a delay line is inserted between the generator output with linear frequency modulation and the automatic power control unit is entered.