RU1800620C - Radio frequency interference suppression adaptive device - Google Patents

Abstract

Usage: radio engineering, radar and communication systems. SUMMARY OF THE INVENTION: in an adaptive interference suppression device, the influence of interference power on the convergence of the adaptation process is reduced, which is especially noticeable when exposed to weak interference, the use of automatic control by a powerful signal in the feedback loop of the auto-compensator reduces the fluctuation of the weight coefficients, which allows to increase the noise immunity. 1 ill.

Description

The invention relates to radio engineering and can be used in radar and communication systems to extract broadband and narrowband signals with arbitrary laws of amplitude and phase modulation against the background of correlated noise interference.

The aim of the invention is to increase the noise immunity of the device.

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

The adaptive interference suppression device comprises a main antenna 1, a compensation antenna 2, low noise amplifiers 3, 4, a high frequency (RF) tee 5, a quadrature modulator 6, a frequency converter 7, a bandpass filter 8, adjustable amplifiers 9, 14, 19, 24, keys 10.15, amplitude detectors 11, 16,20,25, notch filters 12, 17, integration filters 13, 18, 23, 28, narrow-band filters 21, 26, multipliers 30, 36, processor 29, synchronous detectors 31.37 , 22,

27, adjustable attenuators 35, 41, adders 33, 39, search oscillation generators 34, 40, threshold elements 42, 43.

The adaptive interference suppression device comprises a main antenna 1 connected in series, a first low noise amplifier 3, a high frequency tee 5, a frequency converter 7, a bandpass filter 8, the output of which is the output of the device, a compensation antenna 2 connected in series, a second low noise amplifier 4, a quadrature module torus 6, the output of which is connected to another input of the high-frequency tee 5, processor 29, consisting of two channels, each of which contains a search generator connected in series oscillations 34 (40), the first synchronous detector 31 (37), the other input of which is the input of the corresponding channel of the processor 29, the first integrating filter 32 (38) and the adder 33 (39), the output of which is the output of the corresponding channel of the processor 29 and connected to

LO

WITH

oo o o o N3 o

the corresponding input of the quadrature modulator 6, an adjustable attenuator 35 (41), the input and output of which are connected respectively to the output of the search oscillation generator 34 (40) and to the other input of the adder 33 (39). In addition, the device contains multipliers 30 and 36, the outputs of which are connected respectively to the inputs of the first and second channels of the processor, the first and second threshold elements 42 and 43, the inputs of which are connected respectively to the output of the synchronous detector 37 and 31 of the first and second channels of the processor 29, two branches each of which contains a key 10 (15) connected in series, the control input of which is connected to the output of the corresponding threshold element 43 (42), a first amplitude detector 11 (16), a notch filter 12 (17), a second integrator the filter 13 (18) and the first adjustable amplifier 9 (14), the output of which is connected to the input of the key 10 (15) and the first input of the branch number of the multiplier 30 (36) corresponding to the number, and the input of the first adjustable amplifier of each branch 9 (14) is connected with the output of the band-pass filter 8, the other two branches, each of which contains, connected in series with a second amplitude detector 20 (25), a narrow-band filter 21 (26), a second synchronous detector 22 (27), the other input of which is connected to the output of the search oscillator of the corresponding processor channel 29, t there is an integrating filter 23 (28) and a second adjustable amplifier 19 (24), the output of which is connected to the input of the second amplitude detector 20 (25) and to the second input of the branch number of the multiplier 43 (42), and the input of the second adjustable amplifier 19 ( 24) each branch is connected to the output of the bandpass filter.

The device operates as follows .-

When interference Una appears at the inputs of the main and compensation antennas 1,2 at the output of the band-pass filter 8, which determines the noise / noise ratio at the inputs of the adjustable amplifiers 9, 14, a signal appears depending on the level of interference:

D U Uo-UY Wi-UY W2, (1)

where Uo Opo + Oso + Osho - the sum of the interference, signal and noise;

Ui 0ni + and С1 + 0Ш1,

Wi Ci + / Sen- complex weight in common mode;

L / 2 C.2 + P oz complex weight in the quadrature branch;

Ci, 62 weights;

di and az are search oscillations at the output of generators 34 and 40.

/ 3- modulation coefficient.

Due to the independence of the oscillations # 1 and "2, which is achieved by a suitable choice of the waveforms of the generators 34 and 40, the voltages and UciW2 in the in-phase and quadrature branches of the modulator vary independently of each other, i.e. the interference signal is weighted by amplitude and phase. Changes in the amplitude and phase of the interference Uni at the output of modulator 6 are carried out until the gradient of the quality index VP (Wi, L / 2) is equal to zero, which corresponds to the minimum value of the interference power at the outputs of the multipliers 30 and 36. An approximate estimate of the gradient the quality functional VP (Wi, Wa) is carried out by synchronous detectors 31 and 37, the second inputs of which receive oscillation a (from generators 31 and 40. Rectangular waves at a frequency of about 100 (200 ) kHz in which the change the sign (waveform) changes according to the law determined by the pseudorandom sequence. The signal from the outputs of synchronous detectors 31 and 37 is proportional to the frequency derivative of HbiMVP (Wi, W2) (,, feed 38, where

aWi d L / 2

with integrating filters 3, weighting factors Ci and C2 are formed.

The search modulation level / 5 is set by adjustable attenuators 35 and 41.

In the steady state, the voltage at the output of the RF tee 5 is equal to:

AU (U0-UsiCi-UciC2) - -} 3aiUsi + a2Uc2).

(2)

The interference level Д Uni in the first brackets tends to a certain minimum value with a correlation coefficient of interference 1, which is achieved by practically placing an additional antenna vertically above the main antenna and taking out the modulator 6 as close to antenna 2 as possible to ensure high uniformity of the frequency response and phase response in the band interference frequencies at the inputs of the RF tee 5.

To ensure linearity in the conversion of the AU oscillations in the feedback loop, to eliminate the influence of the useful signal on the formation of the weighting factors Ci and C2 and to increase the convergence of the adaptation process, the automatic gain control in the feedback loop is carried out separately for the useful signal and interference. In this case, the weighting factors Ci and C2 are equal to:

c V (cS) 2+ (d) 2

Where.

Gi

KSP

(1 + Ki DC)

j3GiG2U0Ui 1 + / 3GiG2Ul

(3)

K02 (1 + K2 L1Gp2)

/ -modulation coefficient (ft -. „,.

The formation of the GI gain of amplifiers 9, 14 is carried out in steady-state mode in order to reduce the influence of the residual noise AUni on the formation of the control voltage in the AGC loop of amplifiers 9 and 14. The notch filters 12, 17 are attenuated by 40 ... 60 dB oscillations with frequencies cn and cd fluctuation A2 / 42. Since in the steady state mode Un Un «Uc, the control voltage is equal to:

 r K1ARU Usvykh,

where / 5 Ki AGC Ki.

The formation of the control voltage occurs after the adaptation algorithm finds a stationary point in the search process: V Р (Wi, W2) 0. Since practically the gradient V Р (Л / 1, Л / 2) makes fluctuations caused by its approximate estimation in synchronous detectors 31 and 37, the threshold 42h and Ј2, which is selected for the stationary mode, are set in the threshold elements 42 and 43. In the case of V P (Wi,) | n Ј 2, the threshold elements 42 and 43 generate pulses that open the keys 10 and 15. After this, the process of regulating the voltage D U begins with a single estimate of the useful signal Uc.

The gain G2 of the amplifiers 19 and 24 is generated by the remainder of the interference: A Un2 p (Usni + Ucni).

So that the useful signal Uc does not affect the formation of the control voltage, narrow-band filters 21, 26 and old synchronous detectors 22, 27 are included in the feedback loop of the amplifiers 19 and 24. The narrow-band filters 21, 26 are tuned to oscillations a and ar and identify AUni AUn2 AUC

relationship

on the

ULUUuj ULLI

the first inputs of the second synchronous detectors 22,27. After removing the manipulation in blocks 22, 27 at the outputs of the integrating

Aun2

filters 23 and 28 improvement ratio

is in base (B) times. Generally, to gender AUn2

learn ratio

 10 is enough

select the signal base a and "g at the level of 50 ... 100. In this case, the control voltage is:

  rK2PARU, (5)

 steepness of the regulatory characteristic;

K2PARU - gain in the loop of the AGC.

The time constant of the integration filters 13, 18, 23, 28 is chosen equal to:

(6)

35

40

where tst 0.1 ... 1 s is the time constant of the integrating filters 32 and 38.

An analysis of expression (3) shows a significant reduction in the influence of interference power on the convergence of the adaptation process. In this case, the dynamic time constant of the integrating filters 32 and 38, which determines the convergence rate, will be equal to:

45

Tp tst

1 + yySGi С21Я

where Gi, G2 are determined in accordance with

expression (3).

The rate of convergence of the adaptation process increases by 5 ... 10 times. The convergence process is especially reduced when exposed to weak interference.

The introduction of AGC on a useful signal reduced the influence of fluctuations in the SI and C2 weight coefficients and the shift of the balance on the interference compensation efficiency due to a decrease in the influence of the combinational component of Uso Uni in the numerator of expression (3), which made it possible to obtain a gain in the degree of interference compensation by 10 .. .20 dB.

In general, combining AGC systems with respect to interference and a useful signal increased the stability of the feedback loop in a wide dynamic range of changes in the interference powers and a useful signal at the inputs of antennas 1 and 2.

Claims (1)

SUMMARY OF THE INVENTION An adaptive interference suppression device comprising a main antenna connected in series, a first low noise amplifier, a high frequency tee, a frequency converter, a bandpass filter, the output of which is a device output, a compensation antenna connected in series, a second low noise amplifier, a quadrature modulator, the output of which connected to another input of a high-frequency tee, a processor consisting of two channels, each of which contains a gene connected in series search oscillator, the first synchronous detector, the other input of which is the input of the corresponding processor channel, the first integrating filter and the adder, the output of which is the output of the corresponding processor channel and connected to the corresponding input of the quadrature modulator, the adjustable attenuator, the input and output of which are connected respectively with the output of the generator of search oscillations and with another input of the adder, characterized in that, in order to increase the noise immunity, the first and second emnozhiteli whose outputs are connected respectively, with the inputs of the first and second processor channels, the first and second threshold elements, the inputs of which are connected respectively to the output of the synchronous detector of the first and second processor channels, two branches, each of which contains a key connected in series, the control input of which is connected to the output of the corresponding threshold element first amplitude detector, a notch filter, a second integrating filter and a first adjustable amplifier, the output of which is connected to the key input and to the first input of the multiplier branch corresponding to the number, and the input of the first adjustable amplifier of each branch is connected to. the output of the bandpass filter, the other two branches, each of which contains a second amplitude detector connected in series, a narrowband filter, a second synchronous detector, the other input of which is connected to the output of the search oscillation generator of the corresponding processor channel, a third integrating filter and a second adjustable amplifier, the output of which is connected the input of the second amplitude detector and with the second input of the multiplier corresponding to the branch number, and the input of the second adjustable amplifier of each branch is connected n with the output of the bandpass filter. I G.