SU1596265A1 - Apparatus for measuring average rate of frequency change and linearity of modulation characteristics of frequency-modulated oscillators - Google Patents

Abstract

The invention relates to a radio metering technique and can be used to measure the average rate of change of frequency and the linearity of the modulation characteristics of frequency modulated oscillators. The purpose of the invention is to improve the accuracy of measurements and the resolution of the measured parameters. The goal is achieved by applying for mixing the frequency of the analyzed frequency-modulated signal of a harmonic signal of a crystal oscillator 25, as well as by introducing mixers 2, 3, 6, 7, 11, band-pass filters 4, 5, 8, 9, 27, 28, counter 21, oscillator 22 sawtooth voltage, discrete phase shifter 24, phase modulator 23, frequency-modulated oscillator 26. 1 sludge.

Description

The invention relates to the radio technology of the rhythm technique and can be used to measure the rate of change of frequency and the linearity of the modulation characteristics of frequency modulated oscillators. The purpose of the invention is to improve measurement accuracy and resolution with respect to measured parameters. The drawing shows a block diagram of the proposed device. The device contains the test generator 1, the first mixer 2, the second mixer 3, the first band-pass filter 4, the second band-pass filter 5, the third mixer 6, the fourth mixer 7, the third bed: the new filter 8 the fourth band-pass filter 9, the delay line 10, the fifth mixer 1C intermediate frequency amplifier (IF) 12, limiter 13, first frequency detector 14, integrator 15, peak detector 16, low-pass filter 17 (LPF), first amplifier 18, control element 19, local oscillator 20, counter 21, generator 22 sawtooth voltage (phase voltage), phase modulus 23, a discrete phase shifter 24, a crystal oscillator 25, a frequency-modulated oscillator 26, a fifth band-pass filter 27, a sixth band-pass filter 28, a second frequency detector 29, a meter 30, a second amplifier 31, and an indicator first mixer 2, first bandpass filter 4, third mixer 6, third bandpass filter 8, fifth mixer 11, UPCH 12, limiter first frequency detector 14, integrator 15, peak detector 16, first low pass filter 17, first amplifier 18, control element 19, hetero 20, At the same time, the second amplifier 31 and the indicator 32, connected between the output of the local oscillator 20 and the second input of the fifth mixer 11, are connected to the OUTPUT of the integrator 15: a serially connected counter 21, a discrete phase rotator, 24, a phase modulator 23, frequency-modulated generator 26, sixth band-pass filter 28, second mixer 3, second band-pass filter 5, fourth mixer 7, quarter-pass filter 9, the output of the quartz oscillator 25 is connected to the second input of the discrete phase shifter 24, to the output of the local oscillator 2 0 connected in series the second frequency detector 29 and the meter 30, as well as a sawtooth voltage generator 22, the output of which is connected to the second input of the phase modulator 23, between the output of the studied generator 1 and the second inputs of the third 6 and fourth 7 mixers delay line 10c To the output of the phase modulator 23 are connected in series the second frequency detector 29 and the meter 30. The operation of the device is as follows: From the output of the generator 1 to the inputs of the delay line 10 and signal inputs of the first 2 and second 3. mixers receive the analyzed linear-frequency modulated (LFM) signal of the form and, (t) U, + 0.5jBt2 + + j4F (t) dt +% where U, fj ,,, (- amplitude, central frequency, FM speed and initial On the phase of the signal; 4 P (t) is a function describing the Binary impulse frequency deviations from linear law. for which the harmonic signal of the frequency oscillator 26 is displaced; A single-band frequency converter comprising a discrete phase shifter, 24 and a phase modulator 23, in a single band frequency converter, a serum-frequency frequency conversion method based on the phase modulation of the signal being converted by a sawtooth voltage, the repetition frequency of which determines the frequency due to the boundedness of the maximum phase shift when using sufficiently simple pinned phase modulators, it is difficult to obtain a phase shift of 2F Dian, which is not required for serrodine frequency conversion. In this connection, the proposed device uses a stepwise approximation of sawtooth phase modulation, performed on a discrete phase shifter. 24, controlled by the inverse code of the counter 21, the elimination of errors in the stepwise approximation of the sawtooth phase modulation is carried out by applying an additional linear phase modulation of the converted signal on the phase modulator 23 by a sawtooth signal from the output of the sawtooth voltage generator 22

The frequency signal f, jg-Fc from the output of the phase modulator 23 is fed to the modulating input of the frequency-modulated oscillator 26, the harmonic oscillations of the frequency-modulated oscillator 26 with the natural frequency f p are frequency-modulated by the frequency signal f g g FCo The modulated frequency generator ff + kv with the sixth band filter 28 is the component of the difference frequency fr fKe with °

In this case, the chirp signal (1) on the first mixer 2 receives a shift in. frequency by the value of (fp + f "3 Fj.), and at the second mixer 3 by the value of (f-p-f KB s). This frequency of the signal at the output of the first band-pass filter is described by

fzCt)

Kb

l +

fr +

/ iOjt

FC +

+ dF (t), and at the output of the second filter

) f, - f, + FC + + + 4F (t) o

The signal (1) delayed in the delay line 10 is multiplied in the third mixer 6 and the fourth mixer 7 with the signals of the first 4 and second 5 bandpass filters, respectively. From the resultant signals at the outputs of the third and fourth mixers, respectively, the third 8 and fourth

9 bandpass filters are allocated difference frequency signals.

FC + / J 3 + 4F (t)

f. (t)

 Kfl

f, + FC- dF4t).

ffe (t)

signal delay time

where "uh

10 delay lines. These two signals are multiplied in the fifth mixer 11, with the result that the difference frequency of the signal at its output is described by the expression

) 2Fc + (t) Cjj.

(2)

The differential frequency component (2) is made by the intermediate frequency amplifier 12, and the amplitude distortions of the signal that can affect the measurement accuracy are eliminated. the reader 13, the signal from the exit of the chitel edge is fed to the first frequency detector 14, the transition frequency of which is equal to twice the frequency of the quartz crystal

th generator 25 and is 2f

KB At the same time, the average for the pulse duration time the value of the frequency shift of the signal at the output of the intermediate frequency amplifier 12 relatively determines the difference (2 y3i.j- 2 F (-) o) The inertial system of the local oscillator 20, consisting of frequency detector 14, integrates the torus 15, the peak detector 16, the low pass filter 17, the first amplifier 18, and the control element 19 allows you to monitor this difference and ensure that

 2F (3)

since the magnitude of the frequency shift F is proportional to the frequency of the local oscillator FpgT-n F, where n is the discrete number

phases of the discrete phase shifter 24; the time constant of the low-pass filter 17 is chosen significantly. The correlation of deviations from the linear law of the frequency mode is longer

4F (t) o Therefore, the magnitude and sign of the averaged frequency shift of the signal at the input of the first frequency detector 14 relative to the frequency characterizing the difference (3), the hotel

Claims (1)

Claim A device for measuring the average rate of change of frequency and the linearity of the modulation characteristics of the frequency modulated oscillators containing series-connected intermediate frequency amplifier, limiter, first frequency detector, integrator, peak detector, low pass filter, first amplifier, control element, local oscillator, a second frequency detector and a meter connected in series, a 'also a second amplifier and an indicator connected in series, the generator and the first mixer in series, and also the delay line, and the output of the generator under study is connected to the input of the delay line, about aphid h with the fact that, in order to improve the measurement accuracy and resolution, A sequentially connected crystal oscillator, a discrete phase shifter, a phase modulator and a frequency-modulated oscillator, a counter, a sawtooth voltage generator, five band-pass filters, four mixers are introduced, while the sixth band-pass filter, the second mixer, the second band-pass filter, the fourth mixer, and the fourth are connected in series bandpass filter and the fifth mixer, connected in series the first band-pass filter, the third mixer and the third band-pass filter, the inputs of the counter and the pilo generator different voltages are connected to the output of the local oscillator, and their outputs are connected to the control inputs of the discrete phase shifter and phase modulator, the fifth band-pass filter is connected between the output of the frequency-modulated generator and the second input of the first mixer, the second input of the second mixer is connected to the output of the generator being investigated, and the output of the fifth the mixer is connected to the input of the intermediate frequency amplifier, the output of the phase modulator is connected to the input of the second frequency detector, and the output of the integrator is connected to the input th second amplifier, the output of the third bandpass filter coupled to the second input of the fifth mixer output frequency modulated oscillator is connected to the sixth input of the bandpass filter.