SU1548850A1 - Interference compensator - Google Patents

Abstract

The invention relates to communication technology. The purpose of the invention is to improve the noise immunity. The noise canceller includes a noise suppression unit 1, an amplitude limiter 2, a band reject filter 3, a mixer 4, a band filter 5 and a frequency doubler 6. A strong interfering signal and a weak useful signal overlapping with it that has laws of phase modulation act on the input of the compensator. The suppression unit 1 makes the desired signal and combinational noise equal in power, and this mixture passes filter 3, where the useful signal is completely suppressed. The combination product and the interfering signal are then fed to the mixer 4, where the signal from limiter 2 is also received through the doubler 6. As a result, the difference frequency is extracted, the combination product is converted into a useful signal, and the interfering signal is spread over the spectrum. The received signal through the filter 5, tuned to the useful signal, is fed to the output of the compensator. The resulting signal-to-noise ratio is equal to the square of the ratio of the spectral bands of the combinational noise and the useful signal, which ensures increased noise immunity. 5 il.

Description

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The invention relates to a communication technique, namely, to means of extracting weak useful signals with angular modulation from their additive mixture with co-channel strong interfering signals with angular modulation, and can be used in information transmission systems for receiving signals with angular modulation.

The aim of the invention is to improve the noise immunity

Fig. 1 shows a structural electrical canceller circuit; plots diagrams representing signal spectra at various points of the interference canceller | 5 - interference suppressor input block

The noise canceller includes an input 1 suppressor unit, ampliM; The well limiter is 2 "band-reject filter 3, mixer 4, band-pass filter 5 and frequency doubler 6.

The interference suppression input unit (FIG. 3) comprises a first mixer 7, a notch filter 89, a second mixer 9, an amplitude limiter 109, a third mixer 11, and a reference generator 12.

The interference suppression input unit (Fig. 4) contains an amplitude, a cecteter 13, a balanced modulator 4, an amplitude limiter 15.

The interference suppression input unit (FIG. 5) contains an amplifier 16S-reader 17 and an amplitude limiter 1 8.

The interference capacitor works as follows.

At the input there is a strong binge signal with the law of phase modulation (a) and a weak useful signal that overlaps with it in the spectrum with the law of phase modulation (a2) (Fig. 2a).

The output of the suppression input unit 1 is affected by the same power useful signal and combination interference with the phase modulation law (& $) $ which is always wider in spectrum than the useful signal (Fig 26)

The mixture from the output of the input interference suppression unit 1 is passed through a band-reject filter Ze in which the useful signal is completely suppressed f and the distortion by the combination 10

15488504

Noise interference can be interpreted as adding to it its part with the opposite sign lying within the notch band (Fig. 2c, d).

Thus, if we assume that the spectrum of the combination noise is uniform, it can be argued8 that a combination product and an interfering signal8 that is smaller in power are the same as the input of mixer 4 as the combination interference band exceeds the useful signal band.

The second input of the mixer 4 through the frequency doubler 6 from the output of the amplitude limiter 2 (FIG. 2d) is given a signal with the phase modulation law approximately equal to (2-4) (FIG. 2e), since the interference power at the noise compensator input significantly exceeds the power of the useful signal. At the output of mixer 4, where the difference frequency is allocated, a wideband Raman pro20

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A modulation law (2a - ar) turns into a narrowband useful signal with a modulation law (a2), and the narrowband interfering signal spreads across the spectrum, acquiring additional phase modulation (2a) t and its spectrum is approximately equal in width to the spectrum of the combinational interference (fig.2zh).

Thus, at the output of the band-pass filter 5, which is tuned to the useful signal, the power of the interfering product is once again reduced in the ratio of the combinational interference bands and the useful signal

(fig.2z).

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The resulting signal-to-noise ratio is approximately equal to the square of the ratio of the spectral bands of the combinational noise and the useful signal, which ensures increased noise immunity „

Form, l and inventions

An interference canceller, comprising an interference suppression input unit, an interference copy generation channel that includes an amplitude limiter. and the output bandpass filter, which is different. In order to increase the noise protection, it is entered into it

The second input of the mixer 4 through the frequency doubler 6 from the output of the amplitude limiter 2 (FIG. 2d) is given a signal with the phase modulation law approximately equal to (2-4) (FIG. 2e), since the interference power at the noise compensator input significantly exceeds the power of the useful signal. At the output of the mixer 4, where the difference frequency is allocated, the wideband Raman pro5

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A modulation law (2a - ar) turns into a narrowband useful signal with a modulation law (a2), and the narrowband interfering signal spreads across the spectrum, acquiring additional phase modulation (2a) t and its spectrum is approximately equal in width to the spectrum of the combinational interference (fig.2zh).

Thus, at the output of the band-pass filter 5, which is tuned to the useful signal, the power of the interfering product is once again reduced in the ratio of the combinational interference bands and the useful signal

(fig.2z).

i

The resulting signal-to-noise ratio is approximately equal to the square of the ratio of the spectral bands of the combinational noise and the useful signal, which ensures increased noise immunity „

Form, l and inventions

An interference canceller, comprising an interference suppression input unit, an interference copy generation channel that includes an amplitude limiter. and the output bandpass filter, which is different. In order to increase the noise protection, it is entered into it

a connected band reject filter and a mixer connected between the output of the input suppressor unit and the output bandpass

filter, and a frequency doubler, included between the output of the amplitude limiter and the other input of the mixer.

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Editor H (Lazarenko

pha.5

Compiled by L. Zaks

Tehred L. Serdyukova Proofreader N. Revska

Order 145

Circulation 528

VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5

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Claims (1)

An interference compensator comprising an input interference suppression unit, an interference copy generating channel that includes an amplitude limiter »and an output bandpass. | filter, characterized in that, in order to increase the noise immunity, they are introduced in series 5 1548850 connected notch filter and mixer included between the output of the input interference suppression unit and the output bandpass filter, and a frequency doubler connected between the output of the amplitude limiter and the other input of the mixer.