SU926772A1 - Noise suppressing device - Google Patents

Description

(54) INTERFERENCE PROTECTION DEVICE

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The invention relates to radio engineering and can be used in adaptive radio links with a high level of interference.

A device for automatically adjusting the sensitivity (AFC) is known, which contributes to an improvement in the signal-intermodulation interference ratio, comprising a main radio array, including a series-connected controlled linear attenuator, a preselector, a frequency converter, as well as an auxiliary radio path, containing series-connected barrage filter, the first nonlinear element the first band-pass filter, a series-connected amplitude detector and a low-pass filter, as well as a control unit one ,

However, the prior art receiver AFC device does not provide a sufficient signal-to-noise ratio plus intermodulation interference in the main radio path when exposed to a powerful spectrum of interference, located in the pre-selector band, but behind the spectrum of the useful signal.

This is explained, firstly, by the fact that any sufficiently strong interference blocks the useful signal and the linear noise component coming from the antenna, which leads to a decrease in the signal-to-linear noise ratio plus the non-modulus dionic interference in the spectrum of the useful signal. as the second component of linear noise, the intrinsic noise of the radio receiver remains practically unchanged.

Secondly, a change in the amplitude of the interference results, in the presence of blocking, in a parasitic amplitude modulation of a signal equivalent to the effect of the modulating interference. The impact of a modulating interference can be recalculated to an energy equivalent additive interference effect, which also leads to a decrease in

Signal versus line noise plus intermodulation interference.

In addition, the known device is relatively difficult to implement.

The closest in technical essence to the present invention is an interference protection device comprising a series-connected element with adjustable transmission coefficient, the input of which is the device input, a preselector whose output is VLAUT device output, a frequency converter, the first non-linear element, the first band-pass filter and a reader whose output is connected to the control input of an element with an adjustable G23 transfer ratio.

However, this device does not provide a sufficiently large signal-intermodulation interference ratio. In addition, this device does not have sufficient immunity of 1FI blocking the useful signal by pomerhey.

The purpose of the invention is to improve the noise immunity with respect to intermodulation interference and to reduce blocking of the useful signal by interference.

This goal is achieved by the fact that in a device, anti-interference, containing connected in series elements with adjustable transmission coefficient, whose input is the device input, the preselector, whose output is the device output, frequency converter, first non-linear element, first band pass a filter and a subtractor, between the output of the transmitter and the control input of the element with an adjustable transmission coefficient, a second band-pass filter, an amplitude detector, a low-pass filter, and lock control, and between the output of the frequency converter and the other input connected in series Bj itatel third bandpass filter and the second non-linear element. I

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

The anti-interference device contains a variable-gain element 1, a preselector 2, a frequency converter 3, a first non-linear element 4, a first band-pass filter 5, a subtractor 6, a third band-pass 7. 7. a second non-linear element 8, a low-pass filter, a control unit 10, the second band-pass filter 11 and the amplitude detector 12.

The device works as follows.

The amplitude, amplitude-frequency and phase-frequency characteristics of the first nonlinear element 4 and the first bandpass filter connected in series are identical to those of the third bandpass filter 7 and the second nonlinear element 8 connected in series.

The voltage of the signal mixture, noise, concentrated and intermodulation noise from the output of the frequency converter 3 is fed to the input of the first nonlinear element 4 and the third band-pass filter 7. The output of the second band-pass filter 11, which serves to separate the first harmonic and the voltage at its input, will pass a mixture of intermodulation noise arising from the interaction of concentrated noise behind the bandwidth of the first bandpass filter 5 on the first nonlinear element 4 and the residual voltage from blocking the useful o signal, interference.

In order to isolate the residual voltage arising from blocking the useful signal by just one noise, located on the frequency axis beyond the spectrum of the useful signal, the bandwidth of the first band-pass filter 5 and the third band-pass filter 7 must be no greater than the spectrum band of the useful signal.

The voltage from the output of the second band-pass filter 11 is detected by the amplitude detector 12, averaged by the filter 9, the lower frequencies and fed to the input of the control unit 10. In control block 10, in accordance with a control algorithm, a control action is generated on element 1.

The proposed device provides a higher signal-to-noise ratio plus intermodulation interference in the radio path compared to the prototype and, with a high level of concentrated interference.

Claims (2)

1. USSR author's certificate No. 395966, kp. H O3 (5 3/2 O, 1971. 2. US patent number 4126828, cl. H 04 B 1 / 1O, 1978 {npoTOTim). d / move