RU2033670C1 - Digital adaptive multibeam antenna system - Google Patents

Abstract

FIELD: radiolocation. SUBSTANCE: digital adaptive multibeam antenna system has N-element phased array with analog-to-digital converters, unit of formation of additional independent samples, storage, commutation unit, beam forming unit, synchronization unit. Unit of formation of additional independent samples has N complex multipliers. EFFECT: improved protection against active interference. 3 cl, 4 dwg

Description

 The invention relates to radar and can be used to protect radar stations with phased antenna arrays from active interference.

 Known adaptive antenna array containing N multipliers, mixers, amplifiers, filters, combiners and one N-input adder. However, this device does not provide a satisfactory tuning speed.

 The closest in technical essence to the invention is an adaptive multi-beam antenna system, constructed according to a scheme with preliminary interference compensation and subsequent beam formation, containing an N-element phased antenna array (PAR), a vector-matrix multiplication unit, an inverse correlation matrix calculator, scalar units multiplication and sources of control signals. However, with a training sample smaller than the number of interference sources, this device does not provide satisfactory suppression efficiency. Losses in comparison with optimal processing can reach tens of decibels.

 The aim of the invention is to increase the efficiency of the suppression of active interference.

 This is achieved by the fact that in the digital adaptive multipath antenna system containing an N-element phased array with analog-to-digital converters (ADC), a compensation unit and a beamforming unit, an additional sampling unit (BFDV), a memory unit, a switching unit and a synchronization unit are introduced.

 Figure 1 presents the structural diagram of a digital adaptive multipath antenna system; figure 2 is a structural diagram of a block for the formation of additional independent samples; figure 3 is a structural diagram of a switching unit.

 The digital adaptive multi-beam antenna system contains an N-element phased array with ADC 1, BFDV 2, memory unit 3, switching unit 4, compensation unit 5, beamforming unit 6, synchronization unit 7. BFDV 2 contains N complex multipliers (KU) 8. Block 4 switching contains 2N switches 9 type 2/1.

 The device operates as follows.

At the first output of the synchronization unit 7, a meander U _{1 is formed} (see Fig. 4) with a frequency f _t / 2, which is fed to the control input of the ADC. As a result, a discrete sequence of complex sample vectors is formed at the ADC outputs
X (n) [x ₁ (n), x ₂ (n), x _N (n)] ^t with a period of 2 / f _t (where n is a discrete time moment).

(величины b_i хранятся в блоке 3 памяти). На выходе БФДВ 2 формируются векторы комплексных отсчетов
Y(n) [y₁(n), y₂(n),y_N(n)]^т, связанные с Х(n) соотношением
Y(n) ПВX^*(n), где П матрица перестановок;
В diag{b_i}
При этом элементы вектора Y(n) описываются выражением
y_i(n) b_N-i+1x^* _N-i+1(n).The vectors X (n) are fed to the input of the BFDV 2, where each element x _i (n) is subjected to complex conjugation and multiplication by the complex value b _i , i using KU 8

(b _i values are stored in memory block 3). At the output of BFDV 2 are formed vectors of complex samples
Y (n) [y ₁ (n), y ₂ (n), y _N (n)] ^t related to X (n) by the relation
Y (n) PVX ^* (n), where P is the permutation matrix;
In diag {b _i }
Moreover, the elements of the vector Y (n) are described by the expression
y _{i (} n) b _{N-i + 1} x ^* _{N-i + 1} (n).

 At the time preceding the start of adaptation, the initial settings are made in the compensation unit 5.

In adaptation mode, the input of the device receives a signal U ₄ corresponding to a logical zero. At the same time, the control signal U ₂ of the switching unit 4, generated at the second output of the synchronization unit 7, coincides with the signal U ₁ , i.e., it is a meander with a frequency f _t / 2. Being applied to the control inputs of the switches 9, the signal U ₂ determines the connection to the inputs of block 5 for compensating the outputs of the ADC with a positive half-cycle and the outputs of the BFDV 2 with a negative. Thus, at the inputs of the compensation unit 5 with an interval of I / f _t , the values of the samples of the vectors X (n-1), Y (n-1), X (n), Y (n), X (n + 1), Y are set (n + 1)., etc.

In the adaptation mode, at the third output of the synchronization unit 7, a signal U ₃ is generated, which is a meander with a frequency f _t . In accordance with this, the compensation unit 5 operates with a clock frequency f _t The signal U ₄ supplied to the input of the change in the operating mode of the compensation unit 5 provides a write permission to the RAM of the compensation unit 5.

[X(n)X(

)+ Y(n)Y(

)] + Iε
(1)
По окончании режима адаптации сигнал U₄ принимает значение, соответствующее логической единице. При этом на втором выходе блока 7 синхронизации формируется сигнал U₂, совпадающий с сигналом U₄. В результате воздействия логической единицы U₂ на управляющий вход блока 4 коммутации входы блока 5 компенсации подключаются к выходам АЦП. Таким образом, на выходе блока 4 коммутации формируются векторы комплексных отсчетов Х(n) с тактовой частотой f_т/2.In adaptation mode, in block 5 of the compensation, the coefficients of the LDU decomposition of the selective estimate of the correlation matrix (CM) of interference of the form are recurrently generated
R (n)

[X (n) X (

) + Y (n) Y (

)] + Iε
(1)
At the end of the adaptation mode, the signal U ₄ takes _on a value corresponding to a logical unit. In this case, at the second output of the synchronization unit 7, a signal U _{2 is formed} , which coincides with the signal U ₄ . As a result of the influence of the logical unit U ₂ on the control input of the switching unit 4, the inputs of the compensation unit 5 are connected to the outputs of the ADC. Thus, at the output of the switching unit 4, vectors of complex samples X (n) with a clock frequency f _t / 2 are formed.

At the same time, a sequence of pulses U ₃ with a frequency f _t / 2 is formed at the third output of the synchronization unit 7 (see Fig. 4). The signal U ₃ , being fed to the clock input of the compensation unit 5, provides processing of the incoming vectors X (n) with a frequency f _t / 2. In this case, the logical unit at the input of the change in the operating mode of the compensation unit 5 captures the contents of the RAM of the compensation unit 5.

As a result of the transition from the adaptation mode to the processing mode, in the compensation unit 5, the vectors of complex samples of the form are calculated
Z (n) R ^-1 (T) X (n), where T is the volume of the training sample used to obtain the grade.

Next, the vectors Z (n) are input to the beamforming unit 6, where they undergo a linear transformation of the form
Q (n) S ^≈ Z (n), where S is a matrix of size N x K, the i-th column of which S _i is the complex envelope of the signal coming from the expected i-th direction;
To the number of rays.

As a result, a countdown is formed at the i-th complex output of the beamforming unit 6
Q _i (n) S _i ^≈ R ^-1 (t) X (n), (2) corresponding to the output signal of the adaptive spatial filter, which is optimal according to the criterion of the maximum to the signal / (interference + noise) ratio in the steady state.

The estimation of the interference correlation matrix R (n), calculated in accordance with formula (1), takes into account a priori information about the structure of the CM R, the elements of which r _mj are related by
r _{N-j + 1, N-m + 1} f _mj r _mj , (3) where f _mj 1 / (b _{N-m + 1} b * _{N-j + 1} ).

Relation (3) is valid for linear equidistant and flat headlamps with a rectangular and hexagonal arrangement of receiving elements and the amplitude-phase non-identity of their transmission coefficients. In this case, the complex coefficients b _m stored in the memory unit 3 are determined from the expression
b _m a _{N-m + 1} / a * _m , where a _{m is the} complex transmission coefficient of the m-th receiving element.

, где р число помех, [p] ближайшее целое, большее р (для прототипа при Т р).The proposed device allows to achieve a significant increase in the efficiency of noise reduction in a small training sample. In particular, the main gain in efficiency is realized already at T

, where p is the number of interference, [p] is the nearest integer greater than p (for the prototype at T p).

Claims (3)

 1. A DIGITAL ADAPTIVE MULTI-BEAM ANTENNA SYSTEM containing an N-element phased antenna array with analog-to-digital converters (ADCs) at the channel outputs of each element, a compensation unit and a beamforming unit, the outputs of the compensation unit being connected to the corresponding inputs of the beamforming unit, the outputs of which are outputs devices, characterized in that, in order to increase the efficiency of suppressing active interference, the block for the formation of additional independent samples (BFDV), the first group of input whose dow is connected to the corresponding ADC outputs, a memory unit whose outputs are connected to the second group of BFDV inputs, a switching unit, the first group of inputs of which are connected to the corresponding ADC outputs, the second group of inputs is connected to the corresponding BFDV outputs, and the outputs are connected to the corresponding inputs of the compensation unit , a synchronization unit, the input of which is combined with the input of the change in the operating mode of the compensation unit, the first output is connected to the control input of each ADC, the second output is connected to the control input of the block switching, and the third output is connected to the sync input of the compensation unit.  2. The system according to claim 1, characterized in that the BFDV contains N complex multipliers, the direct in-phase and quadrature inputs of the i-th complex multiplier connected respectively to the i-th in-phase and quadrature inputs of the second group, the conjugate in-phase and quadrature inputs of the i-th the complex multiplier are connected respectively to the i-th in-phase and quadrature inputs of the first group, and the common-mode and quadrature outputs of the i-th complex multiplier are connected respectively to the (N-i + 1) -th in-phase and quadrature outputs of the BFDV.  3. The system according to claim 1, characterized in that the switching unit contains 2N switches of type 2/1, the control inputs of which are combined and connected to the control input of the switching unit, and the first input of the (2i-1) -th switch is connected to the i-th in-phase, and the first input of the 2nd i-th switch to the i-th quadrature inputs of the first group, the second input of the (2i-1) -th switch is connected to the i-th in-phase, and the second input of the 2nd i-switch to the i-th quadrature inputs of the second group , the output of the (2i-1) -th switch is connected to the i-th in-phase and quadrature output of the switching unit, i = 1, 2, N.

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