O. V. Bolhovskaya, I. V. Dushko, A. V. Panfilov, A. G. Flaksman

Presence of a ground surface results in multipath propagation of radar signals, which affects the coverage of the radar, especially at small elevation angles. Analytical estimation of the influence of a specific terrain on the radar-s detection coverage is practically impossible. Moreover, the surface relief may vary from one azimuth direction to another. The impact of electrodynamic properties of a surface should also be taken into consideration even though those properties are often known approximately. Therefore it is necessary to use such methods of radar coverage pattern formation that will adaptively take into account properties of the ground surface. Adaptive processing of signals in an antenna array ensuring a maximum output SNR consists in using weight vectors both on receive and on transmit in accordance with amplitude-phase distribution of the echo signal in array elements. This processing method includes two successive operations: 1) maximum likelihood estimation of echo signal amplitude-phase distribution in array elements on the basis of a finite number of input process samples; 2) use of obtained estimates as array weight vectors on transmit and on receive. The effectiveness potential of adaptive processing is achieved subject to ideal estimation of echo signal amplitude-phase distribution in array elements, i.e. with extremely high SNR values. This kind of processing is commonly referred to as optimal. In the present paper, adaptive methods of coverage pattern formation are proposed for a radar with an array antenna operating in the conditions of a ground surface with arbitrary electrodynamic properties and relief. To obtain more accurate estimates of echo signal amplitude-phase distribution in array elements and, hence, weight vectors, the signal-to-noise ratios (SNR) in individual array elements being small, formation of subarrays and use of interpolation procedures is proposed. Simulation results demonstrated rather a high effectiveness of the proposed coverage pattern formation methods as compared with methods that do not employ subarraying.