SU1697261A1 - Device for conjugation of preselector with tunable heterodyne - Google Patents

Abstract

The invention relates to the field of radio engineering and can be used in receiving and measuring equipment. In order to improve noise immunity, a device containing adder 2, mixers 3 and 10, preselector 5, generator b, mixer 10, local oscillator 11, intermediate frequency amplifier 12, modulating signal generator 1, amplitude modulator 4, a third selective amplifier 15, limiter 16, selective amplifiers 13 and 14, mixers 17 and 18, bandpass filters 19 and 20, amplitude detectors 21 and 29, and reference element 23, and generator 6 is dual-frequency and may contain generators 7 and 8 of the first and second frequency 7 and 8 and adder 9, which allows spolzovat auxiliary signal with low noise operating signal to expand the dynamic range and frequency band of capture, improve noise immunity channel co-voltage direct effect on the received signals. 2 Il. ate with

Description

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The invention relates to radio engineering and can be used in receiving and measuring equipment.

The purpose of the invention is to improve the noise immunity of the device.

FIG. 1 shows the structural electrical circuit of the device; in fig. 2 - diagrams illustrating the location of signals on the frequency scale relative to the amplitude-frequency characteristic of the pre-collector.

The device contains a modulating signal generator 1, an adder 2, a first mixer 3, a modulator 4, a preselector 5, a two-frequency generator b made, for example, in the form of generators 7 and 8 of the first and second frequencies respectively and adder 9, the second mixer 10, local oscillator 11 , intermediate frequency amplifier 12, first 13. second 14 and third 15 selective amplifiers, limiter 16, third 17 and fourth 18 mixers, band-pass filters 19 and 20, amplitude detectors 21 and 22, and reference element 23.

The device of automatic conjugation of a preselector with a local oscillator operates as follows.

Signal generators 7 and 8, fixed and frequency stable fi and fa, modulator 4, local oscillator 11 with frequency fr, and first mixer 3 performing heterodyne up-frequency conversion, form amplitude modulated with frequency fM auxiliary radio signals with frequencies fBi r fr ± fi and fB2 fr ± h- The frequencies fi and 12 are chosen respectively below and above the main intermediate frequency of the receiving device by the value of D f, and the value Af is determined from the condition of the frequencies fa-i, fB2 at the centers (or near) transitional amp bands lt-frequency characteristics of the preselector 5 (Fig. 2). the auxiliary signals are fed through the adder 2 and the preselector 5 to the second mixer 10, gdts, they are down-converted to the frequencies s 1 and f2. After preamplification in the intermediate-frequency amplifier 12, the converted signals are fed through the limiter 16 and the first 13 and second 14 selective amplifiers to the inputs of the third 17 and fourth 18 mixers with zero intermediate frequencies, which when fed to the second inputs of signals with frequencies fi and f2 to their the outputs, signals are generated with a frequency fM and levels reflecting the location of the amplitude-frequency characteristic of preselector 5 relative to the frequencies fn1 and FB2. After selection using band-pass filters 19 and 20, signals with frequencies This fM is detected in the amplitude detectors 21 and 22 and sent to the reference element 23,

in which the formation of a control voltage proportional to the difference in the levels of the input signals, through which the preselector 5 is tuned to the desired frequency, is generated. The pre-selector 5 is tuned in frequency until the amplitudes are fully balanced at the inputs of the comparison element 23, the sign of the amplitudes unbalance is determined by the tuning direction.

The influence of the auxiliary signals on the main channel of the device is eliminated as a result of their frequency separation. The effect of input received signals on the interface is reduced by the introduction of

amplitude modulation of auxiliary signals, their selective demodulation in frequency fM, as well as limiting the levels of interfering signals entering the interface and having levels more than

auxiliary signals.

Claims (1)

The invention of the Preselector automatic conjugation device with a tunable local oscillator, containing connected modulating signal generator, modulator, first mixer, adder, another input of which is a device input, a preselector, a second mixer and an intermediate frequency amplifier, a local oscillator whose outputs are connected to other inputs of the first and second mixers, and a generator whose output is connected to A modulator signal input, characterized in that, with a view. increase noise immunity; a series-connected limiter, a first selective amplifier, a third mixer, a first band-pass filter, a first amplitude detector, and the comparison element connected between the intermediate frequency amplifier and the preselector frequency control input, the second selective amplifier, the fourth mixer, are connected in series. a second bandpass filter, a second amplitude detector connected between a level limiter and a second input of the reference element, and a third selective amplifier connected to the output of the amplifiers intermediate frequency, the generator is made of two-frequency, and its outputs of the signals of the first and second frequency are connected respectively to other inputs of the third and fourth mixers. AHC preselect / in / / o / 02 Step 2 /