SU862354A1 - Linear frequency modulated signal generator - Google Patents

Description

(54) GENERATOR OF LINEAR-FREQUENCY MODULATED

SIGNALS

I

The invention relates to radio engineering and can be used to generate linear-frequency-modulated signals in radio communication, as well as in panoramic radio measuring devices.

A linear-frequency-modulated oscillator is known that contains a series-connected sawtooth generator, an adder, a reactive element, a high-frequency generator, a delay line, a mixer, a phase detector, to another input of which the output of the reference oscillator is connected, and a low-pass filter 1.

However, the known generator of linear-frequency-modulated signals does not allow to change, in particular, to increase the rate of change of frequency, since it requires replacing the delay line or the nodes generating the error signal of the reference oscillator and the phase detector. At the same time, it is practically impossible to realize a line with a large amount of delay, regardless of frequency, in a wide frequency band, as a result of which the known generator of linear-frequency-modulated signals has a relatively narrow linear modulation range.

at low frequencies due to the requirement of large delays.

The purpose of the invention is to increase the rate of change of frequency while simultaneously expanding the working frequency band.

To do this, in the generator of linear-frequency-modulated signals, containing, in series, a sawtooth voltage generator, an adder, a reactive element, a high-frequency generator, a delay line, a mixer, a phase detector, to another input of which is connected

10 output of the reference oscillator, and a low-pass filter, between the output of the high-frequency generator and another input of the mixer, a single sideband modulator is introduced, and between the output of the low-pass filter and the other

S input of the adder introduced a differential amplifier. In this case, the other input of the differential amplifier is connected to another output of the sawtooth voltage generator, and the input of the modulation signal of the single-sided modulator is connected to another

20 output reference generator.

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

The linear-frequency-modulated signal generator contains 1 sawtooth voltage generator, adder 2, jet element 3, high frequency generator 4, differential amplifier 5, single-band modulator 6, delay line 7, low pass filter 8, mixer 9, phase detector 10 and the reference generator 11.

The generator of linear-frequency-modulated signals works as follows.

The voltage generated by the sawtooth voltage generator 1, through the adder 2, is supplied to the reactive element 3. A change in the magnitude of the reactivity causes a rearrangement of the high frequency generator 4. From generator 4, the signal goes to delay line 7 and single-sided modulator 6. At the output of the delay line and single-sided modulator, the signals are separated in frequency by a value equal to the frequency of the reference generator 11, the initial phase of the signal from the output of the delay line 7 linearly depends on frequency of the input signal (tp-w, the signal selected in the mixer 9 has a frequency equal to the frequency of the reference oscillator 11 and the initial phase linearly related to the frequency of the high frequency oscillator 4. Therefore, the output voltage of the phase detector 10 at the frequency sweep is directly proportional to the frequency change.The deviation of the law of frequency variation from linear causes a corresponding deviation from the linearity of the signal from the output of the phase detector 10. The error signal selected in the differential amplifier 5, by comparing the signals from the low-pass filter 8 and the generator 1 sawtooth adder 2 adjusts the frequency of the high frequency generator 4.

In the proposed generator of linear frequency modulated signals, the nonlinearity of the frequency tuning is determined by the nonlinearity of the phase-frequency characteristic of the mixer 9 s

and the solution of the phase used characteristics of the phase detector

 u1-25rAfr3 T,

where Af is the restructuring strip; о - permissible nonlinearity of tuning in%; T, required delay. In real cxeiviaxiTf ± 1 °, therefore, 7i -2mt555 (this is the fourth of the 04th ISS, which is realized without any particular difficulty.

Thus, in the proposed generator of linear-frequency-modulated signals, a significant increase in the rate of change of frequency is achieved while simultaneously expanding the working frequency band.

Claims (1)

Invention Formula A linear-frequency-modulated signal generator containing a series-connected sawtooth generator, an adder, a reactive element, a high-frequency generator, a delay line, a mixer, a phase detector, to another input of which the output of the reference oscillator is connected, and a low-pass filter that that, in order to increase the rate of change of frequency while simultaneously expanding the working frequency band, a single-band modulator was inserted between the output of the high-frequency generator and another input of the mixer, and A differential amplifier is inserted between the output of the low-pass filter and another input of the adder, while the other input of the differential amplifier is connected to another output of the sawtooth generator, and the input of the modulation signal of the single-band modulator is connected to another output of the reference oscillator. Sources of information taken into account in the examination 1. USSR author's certificate No. 448565, cl. H 03 C 3/06, 1973 (prototype).