RU2787346C1 - Method for forming antenna pattern for side lobe suppression channel in digital phased antenna array - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to the field of radio engineering, in particular, to methods for providing the specified properties of the radiation patterns of antennas of radio electronic equipment for spatial selection of interference signals received in the side lobes of the main antenna radiation pattern. The effect is achieved due to the fact that the phase distribution of the antenna array is set in such a way that when the geometric beam rotates in the plane of the antenna array, the beginning of which coincides with its geometric center, the phase weight coefficients that specify the shape of the antenna pattern of the side-lobe suppression antenna for the antenna elements, through which the given beam passes are set equal to the angle by which the beam is rotated relative to the initial value, and the amplitude distribution is given by the Gaussian function of the argument equal to the distance from the geometric center of the antenna array.

EFFECT: formation of the directivity diagram of the antenna of the side-lobe suppression channel of a flat digital phased antenna array in the form of a circle or an ellipse.

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Description

The method relates to the field of radio engineering and, specifically, to methods for forming the directivity patterns of digital phased antenna arrays (DFA) with specified properties in the interests of spatial selection of interference signals received in the side lobes of the main antenna directivity pattern. TsPAR is understood as a receiving phased antenna array with digital beamforming, in which the signal from each antenna element of the antenna array is amplified, decomposed into quadrature signals and subjected to analog-to-digital conversion, after which it enters the digital beamforming processor, in which the resulting (resulting) diagram (diagrams) ) directivity (DNA) is formed (formed) by summing the signals of all receiving modules, weighted by complex weighting coefficients that specify the amplitude-phase distribution on the antenna array opening. The method can be used in flat antenna arrays of arbitrary shape with digital beamforming for the formation of a side lobe suppression channel (SBL) in radio-electronic means (RES) of radar, radio communications and radio navigation.

Known methods of protection against impulse noise based on spatial selection, in particular the method of incoherent interference compensation described in [1 - Handbook of radar, ed. M.I. Skolnik. Per. from English. Under the general editorship. B.C. Willows. Book 2. M.: Technosphere, 2014. p. 1206-1209]. The method involves the use of an additional antenna and an additional receiving channel parallel to the main one. The selection of signals is based on a comparison of the amplitude of the signals received by the main and additional channels. By choosing the power gain of the antenna, it is possible to distinguish signals penetrating through the side lobes from signals received by the main lobe of the main channel radiation pattern. By distinguishing the signals, it is possible to suppress the signals received by the side lobes of the main channel radiation pattern. In the description of this method of combating interference, the requirements for the properties of the radiation pattern of the additional antenna are given, but the method for obtaining them is not indicated.

A known method of suppressing interference in the side lobes in antenna arrays with a falling amplitude distribution [2 - Voskresensky D.I. Antennas and microwave devices (designing phased antenna arrays). - 2nd ed., add. and reworked. - M: Radio and communication. 1994. S. 36]. The higher the decay rate of the amplitude distribution to the edges of the aperture, the lower the level of the side lobes of the antenna and the greater the attenuation of interference.

However, the use of a decreasing amplitude distribution leads to a decrease in the antenna gain, which limits the possibilities of this method and is its disadvantage. In addition, the minimum achievable level of side lobes of a real antenna array is limited by non-identity and mutual influence of emitters and receiving paths of individual channels.

A known method of forming a radiation pattern in an antenna system with electronic beam control [3 - Patent 2395141 (RU). Alekseev O.S., Barinov N.N., Moseychuk G.F., Sinani A.I. Method for forming a radiation pattern in an antenna system with electronic beam control. Class H01Q 3/00, published on July 20, 2010], based on the formation of a highly directional scanning radiation pattern of the antenna system of the main channel and a weakly directional non-scanning radiation pattern of the compensation channel antenna, overlapping the level of side radiation of the highly directional radiation pattern, a branch of a part of the microwave signal received a highly directional antenna system of the main channel, as well as adjusting the level and phase of the microwave signal so that when this branched microwave signal is subsequently summed with the signal received by the weakly directional radiation pattern, a dip is formed in the resulting radiation pattern of the weakly directional antenna in the direction of the axis of the highly directional diagram directivity, and when changing the angular position of the beam of the scanning highly directional pattern in the scanning sector and / or operating frequency to form a dip in the resulting pattern The directivity of the weakly directional antenna further changes the amplitude and phase of the coupled microwave signal.

The advantages of the method include a decrease in the direction of the useful signal of the level of the compensation pattern in an antenna system with electronic beam control at any frequency in the operating frequency range, and the disadvantage of this method is the problematic formation of a weakly directional non-scanning pattern, which everywhere overlaps the level of lateral radiation of a highly directional scanning radiation pattern, from which it follows that this method can work in a limited range of angles. With a single antenna element, the weakly directional radiation pattern will be nearly isotropic, but the received signal level will be low. With an increase in the number of antenna elements in a non-scanning radiation pattern, its norm increases, however, as the beam narrows, the interference compensation area is limited. Therefore, to expand the beam, it is necessary to increase the transmission coefficient in the compensation channel and reduce the sensitivity of the receiving system (when the signal is amplified in the compensation channel, noise is also amplified, which increases the likelihood of false positives).

Closer in technical essence to the claimed method (prototype) is a method of forming a compensation pattern in a flat antenna array with electronic beam control [4 - Patent 2567120 (RU). A method for forming a compensation radiation pattern in a flat antenna array with electronic beam control / Larin A.Yu., Litvinov A.V., Mishchenko S.E., Pomysov A.S., Shatsky V.V. Class H01Q 3/26, published 11/10/2015]. The method provides the required excess of the level of the compensation channel antenna pattern over the level of side lobes of a highly directional scanning pattern of a flat antenna array (main channel) in a wide sector of angles while maintaining the sensitivity of the receiving system. The essence of the known method is that signals are received by antenna elements of a flat antenna array with electronic beam scanning and summed, forming a highly directional scanning radiation pattern of a flat antenna array using the selected complex amplitudes of the antenna elements, taking into account the required excess of the level of the compensation radiation pattern over the level of side lobes of a highly directional scanning radiation pattern.

The formation of a weakly directional radiation pattern is carried out by summing the signals of the antenna elements located in the central orthogonal lines of the flat antenna array with complex amplitudes corresponding to the complex amplitudes of the antenna elements of the flat antenna array in the direction of the useful signal source. To form a compensation pattern, the signal corresponding to a highly directional scanning pattern is subtracted from the signal corresponding to a weakly directional pattern multiplied by a weight coefficient equal to the ratio of the norms of the highly directional scanning and weakly directional patterns when the flat antenna array beam is oriented in the direction normal to the opening plane.

The compensation pattern generated by this method provides the required excess of the level of the compensation pattern over the level of the side lobes of the main channel. The side lobes of a flat rectangular antenna array have a maximum level in areas shaped like a pair of orthogonal "ridges", diverging from the center to the edges of the antenna array parallel to its sides (Fig. 1). The generated compensation radiation pattern has a similar comb-like shape. For a flat antenna in the shape of a circle (ellipse), the side lobes of the radiation pattern of the main channel do not have “ridges” (Fig. 2), and therefore the radiation pattern of the compensation channel formed in this way, the comb shape of which is preserved, will not provide the required excess of the antenna radiation pattern level compensation channel above the level of side lobes of a highly directional scanning radiation pattern.

Thus, the disadvantage of the known method is the impossibility of application for antenna arrays with a shape other than rectangular.

As an analogue, the closest known method was chosen [4].

The technical result of the claimed invention is the formation of the antenna pattern of the PBL channel of a flat TsFAR in the form of a circle (ellipse).

At the same time, the analog properties are preserved:

ensuring close to the potential-possible interference/noise ratio at the output of the PBL channel antenna due to the use of all elements of the CFA in the formation of its AP;

formation of the DND of the PBL channel with sufficient accuracy for practice approximating the side lobes of the DND of the main channel;

formation of a deep dip in the DND of the PBL channel in the region of the main beam of the DND of the main channel;

the ability to control the direction of the DND of the PBL channel together with the DND of the main channel.

The following requirements are imposed on the properties of the DND of the PBL channel:

1. as close as possible to axial symmetry (relative to the axis passing through the geometric center of the antenna array perpendicular to its plane);

2. a high degree of approximation of the DND of the PBL channel in the region of the side lobes of the DND of the main channel;

3. the maximum possible gain of the DND of the PBL channel in the region of the side lobes of the DND of the main channel;

4. the minimum possible gain of the PBL channel DND in the region of the main DND beam of the main channel.

5. providing electronic control of the direction of the PBL channel DND, similar to the control of the DND of the main channel.

Requirements 1 and 4 in the invention are provided by the choice of the phase distribution of the CFA of a special form.

Requirements 2 and 3 in the invention are provided by the choice of the amplitude distribution of the CFA of a special type.

The technical result is achieved by the formation of the amplitude-phase distribution of a special type of flat receiving TsFAR.

The method of forming the DND of the PBL channel in the CFAR, in which the electromagnetic wave is received by the antenna elements of a flat phased antenna array, the signal received by each antenna element is amplified, decomposed into quadrature signals, which are subjected to analog-to-digital conversion, the antenna output signal is formed as a function of all received signals ( weighted sum) taking into account the angular direction of orientation of the main beam of the main channel. The proposed method differs in that:

the amplitude weight distribution used in digital diagramming is described by the Gaussian function of the argument equal to the distance from the geometric center of the antenna array to the phase center of the corresponding antenna element;

the phase distribution of the non-deflected antenna of the radiation pattern is set in such a way that when the geometric beam rotates in the plane of the antenna array, the beginning of which coincides with its geometric center, the phase weight coefficients for the antenna elements through which this beam passes are set equal to the angle through which the beam is rotated relative to initial value, any direction of the beam can be chosen as the initial value, for one full rotation of the beam the phase addition changes linearly by 2π radians.

Each signal received by the elementary TFAR antenna is weighted by the corresponding complex weighting coefficient of the amplitude-phase distribution, the weighted signals are summed, the total signal is the output of the PBL channel antenna.

Thus, the claimed method provides the formation of the DND of the PBL channel, which has close to axial symmetry with a "dip" in the direction of the main beam of the DND of the main channel and approximates the level of its side lobes (Fig.3, 4), which makes it possible to form the DND of the PBL channel in a flat TsFAR in the form of a circle (ellipse). Also, in the claimed method, there is no operation of forming the DND of the PBL channel as the difference between two DNDs (weakly directional and highly directional), which distinguishes it from the prototype.

The invention is illustrated by the following drawings:

In FIG. 1 - normalized radiation pattern of the antenna of the main channel of a flat square-shaped TsFAR, ε and β - angular directions measured from the normal to the plane of the antenna.

In FIG. 2 - normalized antenna pattern of the main channel of the flat TsPAR in the form of a circle.

In FIG. 3 - sections of the normalized radiation patterns of the antennas of the main channel (1) and the PBL channel (2).

In FIG. 4 - normalized antenna pattern of the PBL TsFAR channel in the form of a circle.

In FIG. 5 - cross-sections of the normalized directional patterns of the PBL channel for different scale parameter γ:

3 - γ=0.01;

4 - γ=0.015;

5 - γ=0.02;

6 - γ=0.03;

7 - γ=0.04;

8 - γ=0.05;

9 - γ=0.06;

10 - γ=0.1.

In FIG. 6 - phase distribution on the opening of the TsFAR in the form of a circle, x and y - coordinates in the plane of the antenna array.

In FIG. 7 - amplitude distribution on the opening of the CFAR in the form of a circle for γ=0.04.

In FIG. 8 shows the principle of determining the phase weights for the respective antenna elements of the CFAR. On the figure, the numbers indicate:

11 - TsFAR in the form of a circle;

12 - geometric center of the TsFAR;

13 - antenna elements;

14 - the initial direction from which the angle is measured;

15 - geometric beam;

16 - antenna element through which the geometric beam passes. The claimed method includes:

Reception of an electromagnetic wave by elements of a flat phased antenna array. Amplification of each of the signals, its decomposition into quadrature signals and their analog-to-digital conversion. Thus, an array of N complex signals is formed, used in digital diagram formation, which consists in the element-by-element summation of all Ν signals, weighted by complex weight coefficients that specify the amplitude-phase distribution of the CFA.

Complex weight coefficients can be calculated according to the expression

where A _n is the amplitude weighting factor of the signal received by the i-th antenna element;

ϕ _n - phase weighting factor of the signal received by the n-th antenna element, defining the shape of the radiation pattern of the side-lobe suppression antenna;

θ _n is the phase weighting factor of the signal received by the i-th antenna element, which specifies the deviation of the radiation pattern of the side-lobe suppression antenna from the normal to the plane of the antenna array;

N is the number of antenna elements of the digital phased antenna array;

j is the imaginary unit.

When the main beam of the DND of the main channel deviates from the normal to the DND plane due to the control of the phase distribution, similar phase values (θ _n ) are added to the phase distribution of DND of the PBL channel, which ensures the deviation of its directivity pattern similarly to the DND of the main channel (requirement 5 for the DND properties is provided PBL channel).

The amplitude weighting factors are described by the Gaussian function of the argument equal to the distance from the geometric center of the antenna array to the phase center of the nth antenna element

where γ is the scale parameter depending on the level of the side lobes of the DND of the main channel and the law of its change;

x _n , y _n - coordinates of the phase center of the n-th antenna element in a rectangular coordinate system, the center of which is aligned with the geometric center of the antenna array.

The scale parameter γ, which specifies the amplitude distribution, is chosen so that the DND of the PBL channel most accurately approximates the level of the side lobes of the DND of the main channel that is not deviated from the normal to the CFAA plane.

The choice of the scale parameter γ is based on the shape of the radiation pattern of the main channel, which is set by its amplitude-phase distribution. In FIG. Figure 5 shows examples of cross sections of normalized DNDs of the PBL channel for different scale parameters γ. Using this figure, the choice of the most appropriate value of γ can be made. An example of the amplitude distribution at γ=0.04 is shown in Fig. 7.

The phase coefficients ϕ _n are set as follows (Fig. 8). When the geometric beam (15) rotates in the plane of the antenna array (11), the beginning of which coincides with its geometric center (12), the phases ϕ _n of the antenna elements through which this beam (16) passes are set equal to the angle α (Fig. 8) on which the beam is rotated relative to the initial direction (14). Any direction of the beam can be chosen as the initial one. For one complete rotation of the beam, the phase addition changes linearly by 2π radians (360°) in accordance with the expression

where sign is the sign function of the argument, such that

After weighing the received signals by the weight coefficients calculated by the described method, and element-by-element summation of the results, the output complex signal of the PBL channel is formed, which enters the PBL system of the corresponding radio-electronic means. The DND of the PBL channel is shown in Fig. 4. The cross sections of the radiation patterns of the main channel and the PBL channel are shown in FIG. 3.

The results shown in the figures were obtained by mathematical simulation for the following initial data:

antenna array in the form of a circle with a diameter of 0.4 m; structure of placement of antenna elements - hexagonal; distance between antenna elements 0.015 m; total number of antenna elements 2587;

the radiation pattern of one antenna element is isotropic; received signal wavelength 0.03 m;

amplitude distribution of the main channel - cos ² on the pedestal 0.3; the scale parameter of the amplitude distribution of the PBL channel antenna is 0.04.

The radiation patterns were calculated for the range of angles in azimuth β and elevation ε in the range of ±45°.

The simulation results shown (Fig. 3-5) demonstrate the achievement of the claimed technical result.

Literature

1. Handbook of radar, ed. M.I. Skolnik. Per. from English. Under the general editorship. B.C. Willows. Book 2. - M.: Technosphere, 2014.

2. Voskresensky D.I. Antennas and microwave devices (designing phased antenna arrays). - 2nd ed., add. and reworked. - M.: Radio and communications. 1994, p. 36.

3. Patent 2395141 (RU). Alekseev O.S., Barinov N.N., Moseychuk G.F., Sinani A.I. Method for forming a radiation pattern in an antenna system with electronic beam control. Class H01Q 3/00, published 07/20/2010

4. Patent 2567120 (RU). A method for forming a compensation radiation pattern in a flat antenna array with electronic beam control / Larin A.Yu., Litvinov A.V., Mishchenko S.E., Pomysov A.S., Shatsky V.V. Class H01Q 3/26, published 11/10/2015

Claims (1)

A method for forming the radiation pattern of an antenna of a side-lobe suppression channel in a digital phased antenna array, in which an electromagnetic wave is received by antenna elements of a flat phased antenna array, the signal received by each antenna element is amplified, decomposed into quadrature signals, which are subjected to analog-to-digital conversion, the output signal of the antenna is formed as a function of all received signals, taking into account the angular direction of the orientation of the main beam of the main channel, characterized in that the amplitude weight distribution used in digital beamforming is described by the Gaussian function of the argument equal to the distance from the geometric center of the antenna array to the phase center of the corresponding antenna element , and the phase distribution of the directivity diagram of the antenna not deviated from the normal is given such that during the rotation of the geometric beam in the plane of the antenna array, the beginning of which coincides with its geometric center, the phase weight coefficients for the antenna elements through which this beam passes are set equal to the angle by which the beam is rotated relative to the initial value, any direction of the beam is chosen as the initial value, for one full rotation of the beam the phase additive changes linearly by 2π radians, each the signal received by the elementary antenna of the digital phased array antenna is weighted by the corresponding complex weighting coefficient of the amplitude-phase distribution, the weighted signals are summed, the total signal is the output of the antenna of the side-lobe suppression channel.

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