RU1826132C - Noise suppressor - Google Patents

Abstract

Usage: radio engineering, devices for receiving radio signals for various purposes. The inventive interference suppression device comprises multipliers 1, 2, 7, 8, 12 and 13, an adjustable oscillator 3, low-pass filters 4 and 5, a subtractor 6, an integrating element 9, a two-way limiter 10, a loop filter and 90 & deg phase shifters ; 14. The device provides the formation of a compensating signal whose frequency and amplitude correspond to the frequency and amplitude of the noise acting at the input of the device. 1 ill.

Description

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The invention relates to radio engineering and can be used in devices for receiving radio signals for various purposes.

The aim of the invention is to reduce distortion of the useful signal and increase the signal to noise ratio.

The drawing shows a structural diagram of the proposed device.

The device contains a series-connected 3rd multiplier 1, 1st LPF 4, two-way limiter 10 and 6th multiplier 13, as well as 4th multiplier 2, 2nd LPF 5, 5th multiplier 8, loop filter 11 and VCO 14, the second input of the 5th multiplier connected to the output of the 1st low-pass filter 4, the output of the VCO 14 connected to the inputs of the 3rd multiplier 1 and the 6th multiplier 13 and through the phase shifter 3 with the second input of the 4th multiplier 2, the per- the inputs of the 3rd multiplier 1, the 4th multiplier 2 and subtracted 6 are interconnected and are the input of the device, the output of the subtractor 6 is connected to the first input of the 1st multiplier 12 and is the output of the device, the output of which through the integrator 9 is connected to the first input of the 2nd multiplier 7, the output of which is connected to the second input of the subtractor 6, the second inputs of the 2nd multiplier 7 and 1st multiplier 12 are interconnected and the output of the 6th multiplier 13.

The device operates as follows.

It should be noted that blocks 1, 2, 3, 4, 5, 8, 11, and 14 form a coherent demodulator assembled according to the Costas scheme. Its purpose is to isolate the interference from the input signal and noise mixture, and the interference can be either phase-shifted (FM) or frequency-modulated (FM).

Consider the operation of Costas circuits when acting on the input of FM interference and signal

U (t) UnSin ((Wnt + FN

+ UcSin (W ct f p s),

where Φ {0, η} is determined by the law of FM. The system is adjusted in such a way that the signal at the output of the VCO coincides with the noise phase with an accuracy of l, then at the output of the 1st low-pass filter the signal will be equal to Uc

Ui

F + cos (u c-ft n) t +

Uc 2

 sln (0 s - a) n) t 5

10 15 0 5 0

fifty

5

0

5

The main function of the low-pass filter is to filter the harmonic of the total frequency, so its band is chosen large enough so that the delay in the video signal in it is negligible and does not affect the operation of the device.

The result of multiplying these values in the 5th multiplier is the control signal for tuning the VCO. Thus, the device will monitor the interference if Un UC and beats with a frequency (w s - a) n) do not fall into the PLL bandwidth.

When Un Uc at the output of the limiter, the signal will be equal to

U0 sign (cos Ф}, where

sin x i 1 A x 0

 for x 0, and at the output of the 6th multiplier

Ur (t) Ursin (Ф), which, up to the amplitude, coincides with the noise.

Thus, using the Costas circuit, the limiter, and the 6th multiplier, FM interference is regenerated.

Under the influence of the FM input and the signal, the phase of the signal at the VCO output will coincide with the phase of the interference if Un Uc and the modulating frequency of the interference fall into the passband of the PLL system. In the 6th multiplier, in this case, multiplication by a constant occurs, since Φ 0 and sign (cosO) 1.

The regenerated noise is subtracted from the input signal-noise mixture, and its level is adjusted by multiplying in the 2nd multiplier by the weighting factor, which is calculated by correlating the output signal of the device with the regenerated noise. This is done by blocks 12 and 9. Thanks to such an adjustment, a weight factor is set at which the noise level at the output of the device will be minimal.

Thus, in the proposed device, there are no transformations on the signal; therefore, there are no signal distortions.

An increase in the efficiency of the interference pressure in the proposed device is ensured by the fact that the output interference of the device consists of one component — the uncompensated part of the interference in the subtractor. Other components similar to those arising in the AD of the prototype are absent in the proposed device.

- It should be noted that the proposed device, unlike the prototype, allows

Claims (1)

suppress interference having AM. For this, the parameters of the feedback weir ring defining the weight coefficient should be chosen so that the ring has time to track the change in the interference amplitude. SUMMARY OF THE INVENTION An interference suppression device comprising a subtractor, the input and output of which are the input and output of the device, respectively, a first multiplier connected in series, one input of which is connected to the output of the device, an integrating element and a second multiplier, as well as an adjustable oscillator and a frequency adjustment unit and the oscillation phase of the tunable generator for the frequency and phase of the noise, the inputs of which are connected to the input of the device and the output of the tunable generator, and the output to the input of the tunable direct generator, wherein the other inputs of the first and second multipliers together, characterized in that, in order to reduce wanted signal distortion and increasing the signal-to-noise ratio, it administered serially connected two-sided limiter and a third multiplier, the output of which is connected to the combined to the other inputs of the first and second multipliers, the output of the second multiplier is connected to the second input of the subtractor, and the block for adjusting the frequency and phase of oscillations of the tunable generator for the frequency and phase of the noise is made in the form of two circuits connected in series by the multiplier and the loop filter and phase shifter 90 °, each circuit contains an additional multiplier and a low-pass filter connected in series, the phase shifter output 90 ° is connected to another input of the additional multiplier, the second circuit, while input These circuits are combined and are the inputs of the block for adjusting the frequency and phase of oscillation of the tunable generator for the frequency and phase of the noise, connected to the input of the device, the input of the phase shifter and the other input of the additional multiplier of the first circuit are its input connected to the output of the tunable generator, and the output of the tuning block the frequency and phase of the oscillation of the tunable generator for the frequency and phase of the noise is the output of the filter, while the input of the two-way limiter is connected to the output of the low-pass filter of the first enu.