SU987820A1 - Device for selective suppressing of amplitude-modulated noise at the background of signal additive spectrum - Google Patents

Description

 The invention relates to a radiotransfer and can be used in radio receivers.

A device for extracting a useful amplitude-modulated signal from a mixture of a signal and interference with overlapping spectra is known, comprising an input source, a narrowband filter carrying oscillation interference, an electronic switch to the output of which a band-pass filter is connected, and a pulse generator, and an output source of input signals, signals The input of the narrowband filter and one of the inputs of the switch are connected in parallel, the input of the pulse generator is connected to the output of the narrowband filter, and the output is connected to another input of the CC 1 utatora

The suppression of interfering signals in such devices is accomplished by forming input signal samples at the times when the modifying oscillation vanishes. The degree of interference suppression in such a device depends on the duration of the control pulses, the higher the degree of interference suppression. The duration of control pulses cannot be infinitely small due to the fact that

this reduces the transmission coefficient of the device by the useful signal, or a high-speed device for storing the values of the useful signal for short periods of time is required. Therefore, in a known device, a high degree of interference suppression is unattainable.

Closest to the proposed

10 is a device for selectively suppressing AM interference in the background of the additive signal spectrum, containing -. hence the connected signal multiplier (fc-manipulator) and

15 output filter included. the input and output of the device, as well as the filter carrier noise, the input of which is connected to one of the inputs of the signal multiplier. The phase shifter and the control pulse shaper 2 are connected in series with the carrier noise filter.

However, the known device does not provide a high degree of interference suppression in the high-frequency (RF) and microwave (UHF) ranges due to the need to form control pulses with steep edges and a normalized length of i

30 perseverance. The purpose of the invention is to increase the degree of suppression of the AM interference in the RF and microwave bands. This goal is achieved by the fact that a modulator and an output signal filter, as well as an interference carrier filter, whose input is combined with the multiplier input and is the device input, are entered into the selective AM interference suppression device against the background of the additive signal spectrum, which is combined with the multiplier input. to the first input of which the output of the carrier noise filter is connected, the generator, the output of which is connected to the second input of the modulator, the adder, the output of which is connected to another input of the multiplier, and two circuits, each and of the latter consists of a series-connected band-pass filter, an attenuator and a phase shifter, connected between the modulator output and the inputs of the sumat 1-ator. . The schematic diagram shows a structural electrical circuit for selective suppression of AM interference on the background of the additive spectrum of the signal. The device contains sequentially connected multiplier 1 and filter 2 of the output signal, module 3, the first input of which through the filter 4 of the interference carrier is combined with the input of multiplier 1 and the input of the device, and the second input is connected to the output of the generator 5, as well as two circuits, each of which consists of a series-connected band-pass filter 6 (7), an attenuator 8 (9) and a phase shifter 9 (10), p CONNECTIONS to the adder 11. The device operates in the following way,. A mixture of two signals with overlapping spectra is fed to the input of a filter 4 tuned to the carrier frequency of the interference, and the input multiplier is 1. The filter selects the carrier frequency of that interference signal, which is then fed to the modulator 3, where the frequency is controlled by the frequency AtsJ produced generator 5. The signal from the output of the modulator 3 is fed to the inputs of bandpass filters 6 and 7, in which the upper and lower sidebands of the modulated interference oscillations are allocated, which are then adjusted in amplitude by attenuators 8 and 9 and shifted according to the Phase: relative On the other hand, approximately by .130, the exact amplitude ratio and the phase shift value are selected during adjustment by the minimum damage of the attenuators 8 and 9 and the phases of the rotators 9 and 10. Then, the sideband signals are summed up by il and the sum signal is fed to another multiplier input. 1, from the output of which is fed to the filter 2, where a useful component is extracted. Thus, if an additive mixture of the useful signal and interference with overlapping spectra U is received at the input of the device, - UcCt) -U (t) co5Ubfc, where Ug (-t) is the useful signal; UnCtjcosWot - AM interference, the generated signal of the generator 5 at the output of the modulator 3 and, (ao-uu;) + - u, jCos ((i; o + Aii) where yes) 11- frequency of the generator 5, and the multiplier 1 is linear device in relation to the input signal, it is possible to consider the passage through the multiplier 1 of the useful signal and interference separately. and lt) co $ UJot UiCOS ({t; o - /. UJ) t .coc, i ;; (uuo + i.ai) t + 43b UhCt) KU co5AUJt-обob (acjUo-utiJjt - "1i, 1 ( -t) (ua; it4} - -COsi; Uub-t uu;) At UU, 2 and t- ISO, the component of the difference frequency ACtJ in the output signal spectrum is absent. Components with frequencies 2 are filtered by the difference frequency The useful signal Uc (t) is converted as follows: In general, the useful signal is amplitude-frequency modulated with a carrier equal to tUcr with tbUco UJcost e Cl + i CO atH, i - where is the amplitude envelope of the useful signal; m is the index modulation. Conversion of the useful signal without The spectral component with total frequencies filtered by filter 2, as in the case of interference, has the form UpQWcosoicCl-nnicosSl-fcH U cosCa / o-uUjH + U cosBtDot wju.K R С05 tШc Unlcosnt) - (u; o-ucu ) ii cot, UUo i. Cf-tDp (- {h-th cos SI-tX f fc. Carrier frequencies of the obtained amplitude-frequency-modulated k9le

Claims (1)

Claim A device for the selective suppression of amplitude-modulated (AM) interference against the background of an additive signal spectrum, containing a series multiplier and an output signal filter, as well as a carrier noise filter, the input of which is combined with the input of the multiplier and is the input of the device, In addition, in order to increase the degree of suppression of AM noise in the high-frequency and microwave ranges, a modulator is introduced into it, the first input of which is connected to the output of the carrier-interference filter, the generator, the output to otorogo connected to the second input of the modulator, the adder, the output of which is connected to another input of the multiplier, 'and two circuits, each of which consists of ~ series-connected bandpass filter, attenuator and phase shifter, connected between the output of the modulator and the inputs of the adder.