SU1499259A1 - Apparatus for measuring average speed of frequency and linearity change of modulation characteristics of frequency-modulated generators - Google Patents

Abstract

The invention relates to the field of radio metering technology 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 the measurement accuracy and expand the measurement range. The controlled oscillator generates clock pulses, which are counted by the counter 5. The intermediate frequency amplifier 3 separates the difference frequency component from the combinational components from the output of the mixer 2, which through the delay lines 4 is fed to the phase detectors 14 and 15. The reference oscillation for the detector 5 is generated by the generator 26 of the frequency memory block 9, the initial phase of the signal arrives through the construction stage 8 and the adder 24. The self-synchronization loop in the memory block 9 is formed from the delay line 25 and the adder 24. Phase schatel E 1, 6, 10 varies the phase of the signal. The difference signal from the subtracting unit 19 through the video amplifier 23, the integrator 22 is fed to the oscilloscope 21, which is synchronized using a pulse converter 20. The frequency-phase-locked loop is formed by a frequency detector 7, a summing amplifier 13 and an integrator 12. The rate of change of the frequency of the linearly frequency-modulated signal is determined by an electron-counting frequency meter 17. 1 cps f-ly, 4 ill.

Description

one

(21) 4308091 / 2g -21

(22) 21.09.87

(46) 07.08.89. Bul Number 29

(72) N.G.Baturin, D.V. Simakin

and B.V. Strukov

. (53) 621.317 (088.8).

(56) USSR Author's Certificate No. 1241140, cl. G 01 R 23/00, 1986.

USSR Copyright Certificate No. 1442929, class G 01 R 23/00, 1987. (54) DEVICE FOR MEASURING THE AVERAGE RATE OF CHANGE OF FREQUENCY AND LINEARITY OF MODULATING CHARACTERISTICS OF FREQUENCY MODULATED GENERATORS

(57) The invention relates to a radio measuring 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 increase measurement accuracy and expand the measurement range. The controlled generator generates clock pulses, which are counted by counter 5.

The intermediate frequency amplifier 3 separates the difference frequency component from the combinational components from the output of the mixer 2, which through the delay line 4 is fed to the phase detectors 14 and 15. The reference oscillation for the detector 5 is generated by the generator 26 of the frequency memory unit 9, the initial phase the signal enters through the strobe cascade 8 and the adder 24. The self-synchronization loop in memory block 9 is formed from the delay line 25 and the adder 24. The phase of the signal changes with phase shifters 1.6, 10. The difference signal from the readout unit 19 is through the video amplifier 23, the integrator 22 is fed to the oscilloscope 21, which is synchronized using a pulse converter 20. The frequency-phase locked loop of the frequency is formed by a frequency detector 7, a summing amplifier 13 and an integrator 12. The rate of change of the frequency of a linearly frequency-modulated signal is determined by an electron-counting frequency meter 17. 1 ps f-ly, 4 ill.

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The invention relates to a radio metering technique and can be used to measure the rate of change of frequency and linearity and the modulation characteristics of frequency modulated oscillators.

The purpose of the invention is to increase the measurement accuracy and expand the measurement range.

Fig. 1 is a block diagram of a device for measuring the average rate of change of frequency and linearity of the modulation characteristics of frequency modulated oscillators; Fig. 2 is a block diagram of a frequency memory block; FIG. 3 shows timing diagrams explaining the operation of the device; FIG. 4 shows the dependence of the input signal of the phase shifter of its input signal.

A device for measuring the average rate of change of frequency and linearity of the modulation characteristics of frequency-modulated oscillators includes a phase shifter 1, a mixer 2, an intermediate frequency amplifier 3, a delay line 4, a counter 5, a phase shifter 6, a frequency detector 7, a strobe stage 8, a memory block 9 these frequencies, phase shifter 10 on T / 2, controlled oscillator 11, integrator 12, summing amplifier 13, phase detector 14, phase detector 15, delay line 16, electron-counting frequency meter 17, driver 18 pulses, subtracting unit 19, ampl tudny detector 20, an oscilloscope 21, the integrator 22, video amplifier 23

The frequency memory unit 9 comprises an adder 24, a delay line 25 and a synchronized generator 26. (FIG. 2)

Frequency detector 7, summing amplifier 13, integrator 12, controlled generator 11, counter 5, phase shifter 1, mixer 2, intermediate frequency amplifier 3, strobe stage 8, frequency memory unit 9, phase detector 14, subtracting unit 19, video amplifier 23, first integrator 22, oscilloscope 21 are connected in series, the synchronization input of the oscilloscope 21 and the synchronization input of the strobe stage 8 are connected via the amplitude detector 20 and the driver 18 of the pulses to the input of the delay line 16, which is the device input, and to the input phase shifting Ate 6, the second entrance of which soy-. dinene with the second output of the counter 5, the output of the amplifier 3 intermediate frequency is connected via a delay line 4 to the second input of the phase detector 14 and to the input of the phase detector 15, the output of which is connected to the second input of the subtractive unit 19, the output of the phase detector 14 is connected to the second input of the summing amplifier 13 The output of the phase shifter 6 is connected to the second input of the mixer 2, the output of the controlled oscillator 11 is connected to the input of the electron-counting frequency meter 17, the output of the frequency memory unit 9 is connected via the phase shifter 10 to / 2 with the second input Azov detector 15,

As phase shifters 1 and 6, discrete multi-bit range phase shifters with switchable channels of different electrical lengths can be used,

In block 9, frequency memory is connected in series, 2) synchronized generator 26, delay line 25 and adder 24, output of adder 24 connected to input of synchronized generator 26, input of adder 24 is input of frequency memory unit 9, and output of synchronized generator 26 is the output of the frequency memory block.

A device for measuring the average rate of change of frequency and the linearity of the modulation characteristics of frequency-modulated oscillators operates as follows.

The controlled oscillator 11 generates clock pulses with a frequency of f 0.5Fcftb n, where F is the signal frequency offset, n is the number of steps of the sawtooth phase modulation. Gender ,, is chosen so that it is significantly more than the estimated deviations of the instantaneous frequency of the studied linear frequency modulated (LFM) signals from the linear law of the frequency variation over time and is 15-20 MHz. When using the known the time of discrete phase modulators with the number of bits of the control digital code N-6, the number of approximation stages can be n 2 64, n is a binary counter of 5 clock pulses, working with overflow reset, performs under the clock of the controlled oscillator 11. The output direct and inverse codes of the binary counter 5 are supplied as control signals to / discrete phasers 1 and 6, respectively. The high-frequency inputs of discrete phasers 1 and 6 are delayed respectively on line 16 of the delay and the delayed investigated LFM -signal. As a result of the stepwise sawtooth phase modulation of the chirp signal on the discrete phase shifters 1 and 6, the delayed and non-delayed exploration of the CNbix signals is shifted in frequency up and down respectively. The use of two discrete phase shifters 1 and 6 reduces the effect of their inertia on the measurement accuracy by halving the repetition rate of the control code. Spaced apart by frequency

by the value of RS / C delayed and un-. The sustained chirp signals are multiplied at mixer 2. At the output of mixer 2, the combination frequency components are formed, from which intermediate frequency component is separated from the intermediate frequency amplifier 3, and through the delay line 4 is fed to the input of the phase detector. the detector 15. The reference oscillation for the phase detector 15 is generated by a synchronized generator 26 of the frequency memory unit 9, which stores the frequency and

the initial phase of the signal arriving at its input from the output, the amplifier 3 intermediate frequencies through the strobe stage 8 and the adder 24 during the transmitting pulse from the driver 18 pulses, opening the strobe stage B, the duration of the enabling pulse is chosen so that the time in block 9 of the frequency memory is set to stationary mode. The constant frequency of the synchronized generator 26 is maintained for the duration of the chirp of the radio pulse by using a self-synchronization loop, which includes delay line 25 and adder 24. In order not to lose information about the measured parameters at the beginning of the pulse, the signal from the output of the amplifier 3 intermediate frequency served on wto.

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Enter the phase detector 14 through a delay line 4, the delay time of which is equal to the total transient time in mixer 2 and synchronized oscillator 26. The signal from frequency memory block 9 is fed to the second input of phase detector 14.. The output voltage of the phase detector 14 is proportional to the instantaneous phase difference of the oscillations of the synchronized oscillator 26 and the signal from the output of the delay line 4. Due to the inertia of the phase detector 14, the pulse voltage at its output has emissions at the beginning and end of the pulses (Fig. 3, a). These transients, resulting in the loss of part of the information, as well as amplitude distortion of the output signal. the phase detector 14 is compensated at the readout block 19.-For this, a phase detector similar to it is switched on parallel to the phase detector 14

25, the detector 15, to which the reference signal from the memory block 9, the frequency is fed through the phase shifter 10 to 7G / 2, the operating point of the characteristic of the phase shifter 10 from position 1 is moved to position II. (Fig. 4). In this case, the phase shifter 10 becomes insensitive to the phase difference of the input and / or reference signal, and its output signal characterizes the amplitude distortion of the input signal: and its own transients. This signal (Fig. 3.6) is subtracted by the calculation. melting block 19 of the output signal of the phase detector 14. Differential

The 40 signal (Fig. 3c), which characterizes the frequency distortion of the analyzed chirp sign, through the video amplifier 23, the integrator 22 is fed to the observation and measurement on the oscilloscope 21.

45 Synchronization of the oscilloscope 21 and strobe-cascade 8 is carried out by pulses from the generator 18 pulses, start-up. kaida front edge of the envelope of the analyzed chirp radio pulse,

gQ highlighted amplitude detector 20.

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Since the frequency of the synchronized generator 26 can vary within a limited range and in the setting mode only accept discrete values, and the difference frequency at the output of mixer 2 at a wide range of speeds of change in the frequency of the analyzed chirp signals varies widely.

the difference between the oscillation frequencies at the different inputs of the phase detector 14. This leads to errors in the measurement of both the rate of change of frequency and the linearity of the modulation characteristics of frequency-modulated BSh generators.

The change in the difference frequency and phase of the signal at the output of the mixer 2 when analyzing chirp signals with different rates of frequency change is compensated by the inertial circuit of the frequency-phase auto-tuning of the controlled oscillator 1 formed by the frequency detector 7, the summing amplifier 13 and the integrator 12. The output of the intermediate frequency amplifier 3 causes a change in the pulse frequency of the controlled oscillator 11 fp. In this case, the repetition frequency of the control code at the output of the 5 f fn / n counter changes, is equal to the offset frequency of the chirp signal at each of the discrete phasers 1 and 6 Fcf ,, 7c, 0.5FcAB fK, and the difference in the difference frequency at the output of the Fel mixture is compensated 2, therefore, the difference in the frequencies of the signals at the various inputs of the phase detector 14, which occurs when the rate of change of the frequency of the analyzed chirp signal changes. At the same time, the accuracy of compensation of the difference in the oscillation frequency at different inputs of the phase detector 14 increases when the signals from the frequency detector 7 and the phase detector 14 are added to the summing amplifier 13, thus providing frequency-phase self-tuning of the controlled oscillator 11.

The frequency of the controlled oscillator 11 is proportional to the rate of change of the frequency of the analyzed chirp signal, which can be determined by measuring with an electron-counting frequency meter 17.

The introduction of a phase locked loop with an auto-tuning coefficient of 30-50 reduces the error in measuring the frequency (phase) distortion of the linear-frequency-modulated signals by 30-50 times, while the capture band of the systems of frequency-phase auto-tuning becomes much wider than the capture band synchronized

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oscillator 26 and is MHz units, which exceeds the possible initial detuning of the oscillation frequencies at the outputs of the amplifier 3 intermediate frequency and the synchronized oscillator 26. Consequently, the measurement accuracy significantly increases and the range of rates of frequency variations of the analyzed linearly frequency-modulated signals significantly expands. : spade

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Formulas

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A device for measuring the average rate of change of frequency and linearity of the modulation characteristics of frequency-modulated oscillators, containing a series-connected mixer, intermediate frequency amplifier, first delay line, first phase detector and subtraction unit, as well as a video amplifier, first generator, oscilloscope, amplitude detector , second delay line, electron-counting frequency meter, first phase shifter, summing amplifier, serially connected strobe stage and frequency memory block, second The first phase detector, whose output is keyed to the second input of the subtracting unit, the first input of which is connected to the first input of the first phase detector, the input of the strobe stage is connected to the output of the intermediate frequency amplifier, characterized in that, in order to increase the measurement accuracy, expanding the measurement range, a second integrator connected in series, a controlled oscillator, a counter and a second phase shifter, a frequency detector, a pulse shaper, and a third 1/2 phase shifter, whose output is connected, are entered into it the second input of the first phase detector, and the input of which is connected to the second input of the second phase detector and to the output of the frequency memory unit, the output of the reading unit through the serially connected video amplifier and the first integrator connected to the first input of the oscilloscope, the second input of which is connected to the second input of the strobe the cascade and the output of the pulse driver, the input is connected to the output of the amplitude detector to-cheaply.

9 1499259

the input of which is connected through the first phase shifter to the first input of the mixer and through the second delay line to the second input of the second phase rotation, whose output is connected to the second input of the mixer, the second output of the counter is connected to the second input of the second phase shifter, the input of the counter is connected to the input electronically calculating} about

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frequency counter, the output of the intermediate frequency amplifier is connected via a frequency detector to the first input of a summing amplifier, the output of which is connected to the input of the second integrator, and the second input of which is connected to the second input of the subtractive unit, and the input of the second delay line is the input of the device.

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Claims (1)

The claims 15 A device for measuring the average rate of change of frequency and linearity of the modulation characteristics of frequency-modulated generators, 20 comprising a series-connected mixer, an intermediate frequency amplifier, a first delay line, a first phase detector and a subtracting unit, as well as a video amplifier, 25 first generator, an oscilloscope, an amplitude detector, a second delay line, an electronically counted frequency meter, a first phase shifter, a summing amplifier, sequentially connected 30 cascade strobe and a frequency memory unit, sec the first phase detector, the output of which is connected to the second input of the subtracting unit, the first input of which is connected to the first input 35 of the first phase detector, the input of the strobe cascade is connected to the output of the intermediate frequency amplifier, characterized in that, in order to increase the measurement accuracy and expand the range of measurements, a second integrator, a controlled generator, a counter and a second phase shifter, a frequency detector j5 torr, a pulse shaper and a third phase shifter at 77/2, an output of a shaft limit by measuring the electron-counting frequency meter 17. The introduction of a phase locked loop with a locked loop coefficient of K = 30-50 allows one to reduce the error in measuring the frequency (phase) distortions of linearly-frequency-modulated signals by 30-50 times, while the capture band of frequency-phase locked loop systems becomes much wider than which is connected with the second input of the first phase detector, and the input of which is connected to the second input of the second phase detector and with the output of the frequency memory unit, the output of the subtracting unit through series-connected video amplifiers Only the first integrator is connected to the first input of the oscilloscope, the second input of which is connected to the second input of the cascade strobe and the output of the Pulse former, the input of which is connected to the capture strip synchronized with the output of the amplitude detector, the input of which is connected through the first phase shifter to the first input of the mixer and through the second a delay line to the second input of the second phase shifter, the output of which is connected to the second input of the mixer, the second output of the counter is connected to the second input of the second phase shifter, the input of the counter is connected is connected to the input of the electronically counted frequency meter, the output of the intermediate-frequency amplifier through the frequency detector is connected to the first input of the summing amplifier, the output of which is connected to the input of the second integrator, and the second input of which is connected to the second input of the subtracting unit, the input of the second line Delay J0 is the input of the device.