RU30044U1 - Adaptive interference canceller - Google Patents

Description

Adaptive noise canceller.

The utility model relates to radio communications, in particular, to receiving devices with a controlled antenna pattern.

Interference cancellers are known in which a weighted summation of oscillations (signal and interference) coming from different directions is used to suppress interference. For example, in the book Adaptive Interference Compensation in Communication Channels edited by Yu.I. Losev, M., Radio and Communications, 1988, p.22, an adaptive interference compensator is described which implements a gradient method for generating the weight coefficients of the receiving antenna array.

A significant drawback of this compensator is the dependence of the rate of convergence of the weighting coefficients of the algorithm on the power of the incoming signals (the lower the signal level, the lower the rate of convergence), which, in the presence of fast fading (fading) in the propagation channel, does not provide the required amount of interference suppression.

The closest in technical essence to the proposed one is the compensator described in the patent of the Russian Federation №2115233 (B. I. No. 19 for 1998), adopted as a prototype.

In FIG. 1 shows a structural diagram of a compensator-prototype, where it is indicated:

1, 2 and 5 - normalizing amplify. 1sh;

6- inverter amplifier;

4, 7 and 8 - correlation (quadrature) filters;

10-amplitude limiter;

In FIG. 2 shows a diagram of the correlation filter, where it is indicated: 1 - phase shifter 90, 2, 4,5 and 7 - multipliers, 3 and 6 integrators, 8 - adder.

voltages that are highly correlated with the voltage applied to the input of the filter. This is done by summing the quadrature components of the reference voltage with weighting coefficients equal to the correlation value (values of mutual correlation functions) of the input and reference voltage components. These weights are formed in correlators consisting of multipliers 4 and 7 and integrators 3 and 6.

Device prototype works as follows.

For each of the Druh. the inputs of the device receives a mixture of signal and interference, for example, from antennas spaced apart or polarized. Moreover, their frequency spectra can overlap significantly, but the sources must be spaced in space in azimuth. The difference in the angles of arrival of the signal and interference leads to a difference in the phase difference of the signal and the interference between the antennas, which makes it possible in principle to extract a useful signal from the input mixture.

Due to the action of negative feedback through the amplifier-inverter 6, the voltages at the output of the cz of the 3 and at the reference input of the correlation filter 4 turn out to be mutually uncorrelated, and due to the normalizing amplifiers, also with constant levels. Thus, the voltage at the reference inputs of the correlation filters 7 and 8 are orthonormal. Due to this, the adaptation speed of the compensator becomes constant, independent of the signal / noise ratio.

A reference signal is generated at the output of the amplitude limiter 10. The difference between the output and reference voltages at the output of the subtractor 11 is the error signal. This signal is fed to the inputs of the correlation filters 7 and 8, at the outputs of which mixtures of signal and noise are formed, the sum of which approaches the shape of the reference signal. Thus, during the adaptation process, the weight coefficients at the inputs of the weight multipliers 2 and 5 (FIG. 2) of the correlation filters 7 and 8 (FIG. 1) are set so that the error signal has a minimum value.

MSHM

Then, signal retention continues even when the signal-to-noise ratio changes over a wide dynamic range. In accordance with the description of the prototype, its scheme can also be represented in the form depicted in Fig.Z, where it is indicated:

1, 2 and 6 - normalizing amplifiers, 3 and 10 - adders, 4.8 and 9 - weight multipliers, 5 and 7 - devices for the formation of weight coefficients (UVVK), 10 - subtractor, 12 - amplitude limiter.

The main disadvantage of the prototype device is the ability to intercept and hold for interference, especially when the interference also has a constant envelope (signal-like interference). The probability of this event is greater, the smaller the spatial differences (angle of arrival) of the signal and interference.

To eliminate this drawback, a device containing the first and second normalized amplifiers, the outputs of which are connected respectively to the first and second inputs of the first compensator, containing the first and second weight multipliers, the outputs of which are connected to the corresponding inputs of the adder, the output of which is connected to the input of the amplitude limiter the output of which is the first output of the device, while the first inputs of the first and second weight multipliers are connected to the first and second inputs of the forming device the weights respectively and are the first and second inputs of the first compensator, in addition, the first and second outputs of the device for forming the weight coefficients are connected to the second inputs of the first and second weight multipliers, respectively, while the third input of the device for forming the weight factors is connected to the output of the amplitude limiter, the second a compensator identical to the first, a threshold block and a switch connected in series, as well as an additional compensator. The additional compensator contains the first and second correlators, the outputs of which are connected to the corresponding inputs of the divider. The first inputs of both correlators, the second input of the second correlator and the input of the amplifier-inverter are connected and are the reference input of the additional compensator connected to the first output of the device. Serially connected amplifier-inverter, weight multiplier and adder, the second input of which is connected to the second input of the first correlator and is the main input of the additional compensator connected to the output of the second compensator and, in addition, connected to the second input of the switch, which is the second output of the device. The output of the divider is connected to the second input of the weight multiplier and the input of the threshold block. The output of the adder is connected to the third input of the switch, the output of which is connected to the third input of the device for generating the weight coefficients of the second compensator, the first and second inputs of which are connected to the outputs of the first and second normalizing amplifiers, respectively.

The essence of the claimed device consists in the implementation of two) outputs, on one of which a useful signal is allocated, and on the second - an interference. In this case, when interception occurs, the useful signal is not suppressed, but simply appears on another output.

The scheme of the claimed device is shown in figure 4, where it is indicated:

1 and 2 - normalizing amplifiers;

3 and 8 are devices for generating weighting factors;

4,5,6,7 and 18 - weight multipliers;

9.10 and 19 - adders;

11 and 13 - amplitude limiters;

12 and 15 - correlators;

14 - switch;

16-divider

17 - amplifier inverter;

20 threshold device.

I - the first (leading) compensator;

II - the second (slave) compensator;

III - additional compensator.

The proposed device contains the first 1 and second 2 normalizing amplifiers, the first (master) I, the second (slave) II and additional Ш compensators, as well as the threshold block 20 and the switch 14. The first compensator I contains the first 4 and second 5 weight multipliers, the outputs of which are connected to the inputs of the adder 9,

the output of which is connected to the input of the amplitude limiter 11, the output of which is connected to the third input of the UVVK 3 and is the output of the first compensator I and the first output of the device. Both compensators are identical, and the inputs of the weight multipliers 6 and 7 of the second compensator II are connected to the outputs of the normalizing amplifiers 1 and 2. The output of the second compensator P is the output of the amplitude limiter 13 and the main input of the additional compensator III.

The additional compensator contains the first 12 and second 15 correlators, the first inputs of which and the second input of the second correlator 15, as well as the input of the amplifier - inverter 17 are connected and are a reference input connected to the output of the first compensator. In addition, the amplifier - inverter 1, the weight multiplier are connected in series 18 and the adder 19, the output of which is connected to the second input of the switch 14, and its first input with the second inputs of the first correlator 12, szpu1 of the 19, and also is the main input of the additional compensator III and the output of the device. The outputs of the correlators 12 and 15 are connected to the corresponding inputs of the divider 16, the output of which is connected to the input of the threshold block and the second input of the weight multiplier 18. The output of the commutator 14 is connected to the third input of the UVVK 8, which is the third input of the second compensator P. The device works in the following way.

Mixtures of signal and interference from two spaced antennas are fed through normalizing amplifiers 1 and 2, ensuring constant input power, and are fed to the inputs of two identical noise cancellers, one of which is the master (I) and the other is the slave (II).

The first (leading) compensator I contains weight multipliers 4 and 5, the adder 9, UFVK 3 and amplitude limiter 11. The second (slave) II compensator contains weight multipliers 7 and 6, szator 10, UFVK 8 and amplitude limiter 13.

in the first compensator I, the reference oscillation is formed from the output

the oscillator of the compensator with the help of the amplitude limiter 11 and goes directly to UVVK 3, and in the second II - with the help of the pulser) of the amplitude limiter 13 and the additional compensator III. This additional compensator P1 contains correlators 12 and 15, a divider 16, an amplifier-inverter 17, a multiplier 18, and an adder 19. The output of the first amplitude limiter (the first output of the device) is connected to the reference input of the additional compensator III, and the output of the second amplitude limiter is connected to the main input ( second device output).

At the output of the additional compensator (the output of the adder 19), an oscillation is formed that is uncorrelated with the oscillation at its reference input. Thus, if the first and second compensators are captured by the same oscillation (for example, by the noise prevailing at that moment) and it is present simultaneously at both outputs of the device, then the predominant component of the mixture (interference) is suppressed at the output of the additional compensator, and a smaller component is released - in this case, a useful signal. He enters through the switch 14 as a reference oscillation in UVVK 8 of the second compensator. As a result, at the second output of the device, after a transient time determined by the inertia of the correlators 12 and 15, a useful signal appears.

An additional compensator plays the role of a kind of “ejector of the reference oscillation of the first compensator from the reference oscillation of the second compensator. In other words, the output of the first (leading) compensator I controls the composition of the oscillations at the output of the second (slave) compensator II using an additional compensator III.

However, the output of the second (slave) compensator I is not optimal, since it uses the output signal of the additional compensator III, which is subject to significant fluctuations caused by fluctuations in the weight coefficient of this compensator, as a reference signal. To eliminate this drawback, a switch 14 is introduced into the proposed device, connecting to the UVVK 3 reference input or an additional output

pensioner (in case of capture by the first and second compensator for the same component

the input mixture), or the output of the amplitude limiter 13 (in the case of capture by the first and second compensator for different components of the input mixture). The criterion for evaluating the capture for different or for the same component is the value of the correlation function between the outputs of the device, which serves as a weight coefficient in the additional compensator (output of the divider 16). Therefore, by the magnitude of this coefficient it is possible to judge which vibrations are allocated at the device outputs - the same or different, and depending on this, connect one or the other standard vibrations for the second compensator.

If different vibrations are distinguished, then the average value of this coefficient is equal to zero, however, due to the limited averaging time in the correlators 12 and 15, its instantaneous values experience fluctuations. These fluctuations lead to a distortion of the reference oscillation of the second compensator and, consequently, to a distortion of the oscillations at the second output. At the same time, at the output of the amplitude limiter 13 s), there is a cleaner reference oscillation. Therefore, to eliminate the indicated fluctuations, the output of the amplitude limiter 13 is connected to the reference input of the device for generating weight coefficients 8 using the switch 14, while the output voltage of the threshold device 20 is used as the control voltage of the switch. The first and second compensators work completely independently until the allocation to them continues yields of different components of the mixture.

By as soon as the same oscillation (for example, interference) begins to appear at the second output of the device as at the first output, the voltage value (the value of the correlation function) at the input of the threshold device 20 increases, which leads to its operation. The control voltage of the threshold device switches the switch 14 to its original state and the reference oscillation will be supplied from the output of the additional compensator (output of the adder 19), forcing the second compensator to return to the allocation of another component of the mixture (signal). After that, the switch again switches, giving as a reference the output of the amplitude limiter 13.

The implementation of functional blocks is obvious from their name, except for the device

UVVK.

The best option for constructing UVVK is the implementation of the well-known algorithm for direct inversion of the correlation matrix of input signals, described, for example, in the book above mentioned on page 52. In accordance with this algorithm, the vector of weighting coefficients of the compensator W, minimizing the deviation of the output voltage from the reference oscillation, is calculated as follows:

W (, (1)

where RXX is the correlation matrix of input oscillations

RP, V CCC

"To

V / 4i CZTs and 2U

U, And the voltage at the first and second input of the compensator is a sign of complex conjugation, the upper line indicates the operation of averaging over time, carried out with the help of a low-pass filter. about d (d, d) (UjZgUjZg) is the vector of correlation of the standard with the input signals; t is the transpose sign. Elements of the vector of weights are calculated as follows: Ш.-04 1 st S YRK R 2

Claims (1)

An adaptive interference compensator comprising first and second normalizing amplifiers, the outputs of which are connected respectively to the first and second inputs of the first compensator, containing the first and second weight multipliers, the outputs of which are connected to the corresponding inputs of the adder, the output of which is connected to the input of the amplitude limiter, the output of which is the first the output of the device, while the first inputs of the first and second weight multipliers are connected to the first and second inputs of the device for forming the weight coefficient respectively, and are the first and second inputs of the first compensator, in addition, the first and second outputs of the device for generating weight coefficients are connected to the second inputs of the first and second weight multipliers, respectively, and the third input of the device for generating weight factors is connected to the output of the amplitude limiter, characterized in that a second compensator is introduced, identical to the first, threshold block and switch are connected in series, as well as an additional compensator containing the first and the second correlators, the outputs of which are connected to the corresponding inputs of the divider, the first inputs of both correlators, the second input of the second correlator and the input of the amplifier-inverter are connected and are the reference input of the additional compensator, which is connected to the first output of the device, serially connected amplifier-inverter, weight multiplier and adder the second input of which is connected to the second input of the first correlator and is the main input of the additional compensator, the output of the divider is connected to the second input of the new multiplier and the input of the threshold block, the adder output is connected to the second input of the switch, the output of which is connected to the third input of the device for generating the weight coefficients of the second compensator, the first and second inputs of which are connected to the outputs of the first and second normalizing amplifiers, respectively.