SU1476397A1 - Method for measuring mean frequency variation rate and linearity of modulation characteristics of frequency-modulated oscillators - Google Patents

Abstract

This invention relates to a radio measuring technique. The purpose of the invention is to expand the frequency range of the analyzed signals and simplify the device. To achieve the goal, a second low-pass filter 5, a generator 6, a second mixer 9, a first low-pass filter 10, a first delay line 11, a third mixer 12, and a second one were introduced into the device for measuring the average rate of change of frequency and the linearity of the modulation characteristics of frequency-modulated oscillators. frequency multiplier 19, first frequency multiplier 23. The device also contains the first mixer 1, intermediate frequency amplifier 2, strobe stage 3, frequency meter 4, frequency divider 7, frequency memory unit 8, phase shifter 13, switch 14, oscillographic indicator 15, phase detector 16, second delay line 17, generator 18 sawtooth voltages, video amplifier 20, integrator 21, frequency-modulated oscillator 22. The device can be used in metrology and instrumentation systems. 1 il.

Description

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11476397

This invention relates to a radio measuring technique.

The aim of the invention is to expand the frequency range of the analyzed signals and simplify the device.

The drawing shows the functional diagram of the device.

The device contains p. Ryv mixer 1, intermediate frequency amplifier 2, strobe cascade 3, frequency meter 4, second low-pass filter 5, generator 6, frequency divider 7, frequency memory block 8, second mixer 9, first low-pass filter 10, first delay line 11, third mixer 12, phase shifter 13, switch 14, oscillographic indicator 15, phase detector 16, second delay line 17, sawtooth generator 18, second frequency multiplier 19, video amplifier 20, integrator 21, frequencies-: but modulated oscillator 22, first smart resident of 23 frequencies.

Generator 6, frequency divider 7, sawtooth voltage generator 18, frequency modulated generator 22, second mixer 9, first low-pass filter 10, first delay line 11, first mixer 1, intermediate frequency amplifier 2, strobe-cascade 3, are connected in series frequency memory unit 8, the signal of the frequency-modulated oscillator 22 under study is fed to the input of second-mixer mixer 9. The second frequency multiplier 19 increases the frequency of the generator 6 n times, and the first frequency multiplier 23 increases (n-1) times. As a result, the combination component of the difference frequency at the output of the third mixer 12 is the spectrum of the signal of the frequency-modulated generator 22, shifted by the frequency nfa, and at the output of the second mixer 9 - by

15 frequency (n-l) fa. The spectral components of the difference frequency from the outputs of the second mixer 9 and the third mixture of bodies 12 are separated, respectively, by the first low-pass filter 10 and

20 second filter 5 low frequencies.

The spectra of the signals from the outputs of the first low-pass filter and the second low-pass filter are separated in frequency by fa. As a result of the alternation of these signals on the first mixer 1, the combination components are formed. The difference frequency signal fa-fuf (where uf 5 is an additional frequency offset due to the delay

30 of the first delay line 11) is allocated by the intermediate frequency amplifier 2, through the second delay line 17 is fed to the input of the phase detector 16. Memorizing the signal frequency from the trigger 13, switch 14, Yes the intermediate frequency amplifier 2

Zyw detector 16, integrator 21, video amplifier 20, oscillographic indicator 15, the second input of which is connected to the output of the frequency divider, the output of the frequency-modulated 0 generator 22 is connected in series with the third mixer 12, the second low-pass filter 5, the output of which connected to the second input is primarily implemented in frequency memory unit 8. To do this, after the end of the transients in the mixer 1, the gate-cascade 3 is fed with an enable pulse from the output of the frequency divider 7 and the signal from the intermediate frequency amplifier 2 is fed through the strobe cascade 3 to the synchronized generator of the frequency memory block 8. In order not to signal the frequency-modulated generator 22 under study, it enters the input of the second-mixer of the mixer 9. The second frequency multiplier 19 increases the frequency of the generator 6 n times, and the first frequency multiplier 23 - (n-1) times. As a consequence, the combination component of the difference frequency at the output of the third mixer 12 is the spectrum of the signal of the frequency-modulated generator 22, shifted by the frequency nfa, and at the output of the second mixer 9 - by

5 frequency (n-l) fa. The spectral components of the difference frequency from the outputs of the second mixer 9 and the third mixer 12 are separated, respectively, by the first low-pass filter 10 and

0 second low pass filter 5.

The spectra of the signals from the outputs of the first low-pass filter and the second low-pass filter are separated in frequency by fa. As a result of the alternation of these signals, combination components are formed on the first mixer 1. The difference frequency signal fa-fuf (where uf 5 is an additional frequency offset due to the delay

0 of the first delay line 11) is allocated by the intermediate frequency amplifier 2, through the second delay line 17 is fed to the input of the phase detector 16. The signal frequency is stored from the output in block 8 of the frequency memory. To do this, after the end of the transients in the mixer 1, the gate-cascade 3 is fed with an enable pulse from the output of the frequency divider 7 and the signal from the intermediate frequency amplifier 2 is fed through the strobe cascade 3 to the synchronized generator of the frequency memory block 8. So as not to

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The mixer, the output of the generator 6, connect the measured parameters at the beginning of the pulse, the signal from the output of the intermediate frequency amplifier 2 is fed to the second input of the phase detector J6 via the delay line 17. The signal from the frequency memory block 8 through the phase shifter 13 to W12 and the switch 14 is fed to the first input of the phase detector 16. The output signal from the phase detector 16 is proportional to the instantaneous phase difference of the oscillations from the output of the frequency memory block 8 and the output signal of the amplifier 2 intermediate frequency , through integrator 21 and video amplifier

dinene with combined inputs of the second multiplier 19 frequency and the first frequency multiplier 23, the outputs of which are connected to the second inputs of the third mixer 12 and the second mixer 9, respectively. The output of the intermediate frequency amplifier 2 through the second delay line 17 is connected to the second input of the phase detector 16, the output of block 8 the frequency memory is connected to the inputs of the frequency meter 4 and the switch 14.

The device works as follows.

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20 is fed to an oscillographic indicator 15, on the screen of which one can observe deviations of the modulation characteristic of the studied FM generator 22 from the linear law

To take into account the parasitic amplitude modulation of the signal at the output of the intermediate frequency amplifier 2, switch 14 is required. The signal from the output of the frequency memory block 8 is fed to the input of the phase detector 16, minus the phase shifter 13. Thus, the operating point of the phase detector 16 is shifted to the region where The phase detector is practically insensitive to changes in the phase difference of the input oscillations and its output signal will be proportional to the magnitude of the parasitic amplitude modulation. Subtracting the result of this measurement from the result obtained taking into account the influence of the parasitic modulation amplitude provides an increase in the measurement of the deviation of the modulation characteristic of the frequency-modulated generator 22 under study from the linear law.

Thus, the device makes it possible to measure the average rate of change of frequency and linearity of the modulation characteristics of frequency-modulated oscillators operating at both microwave and intermediate frequencies, while simpler elements are used in comparison with the prototype.

Claims (1)

Invention Formula Device for measuring average rate of change of frequency and linearity of modulation characteristics 0 five 0 5- Q 0 frequency modulated oscillators containing the first mixer, an intermediate frequency amplifier, a strobe stage, a frequency memory unit, a phase shifter, a switch, a phase detector, an integrator, a video amplifier, an oscillographic indicator, the second input of which is connected to the output of the frequency divider and the input a sawtooth generator, the output of which is connected to the input of a frequency-modulated generator, while the output of the intermediate frequency amplifier is connected to the second input of the phase detector And through the second delay line, and the output of the frequency memory unit is connected to the input of the frequency meter and the second input of the switch, the second input of the strobe stage is connected to the second output of the frequency divider, characterized in that, in order to expand the frequency range of the analyzed signals and simplify the device, introduced in series the first frequency multiplier, the second mixer and the first low-pass filter, as well as the second frequency multiplier connected in series, the third mixer and the second low-pass filter, with In this case, the inputs of the first and second frequency multipliers are connected to the output of the generator and the input of the frequency splitter, the second inputs of the second and third mixers are connected to the output of the frequency-modulated generator, the output of the first low-pass filter is connected to the first input of the first mixer via the first delay line, and the output of the second filter low pass is connected to the second input of the first mixer.