F.K. Povolotskij - Ph.D. (Eng.), Leading Specialist, JSC "MSDB "Almaz-Antey?. E-mail: SIDOROVA@ecorg.ru

The present study is devoted to the problem of suppression of a jamming signal arriving from a direction close to the direction of the main maximum of the antenna pattern (AP). An angular range including the main lobe and the first two or three sidelobes is investigated. A square 16-module phased array with a uniform amplitude and linear phase distribution of the field in the antenna aperture is used as an antenna. With a knowledge of the direction toward the jammer located in the horizontal plane of the AP central section, the jamming signal is suppressed by a single introduction of the required 180° phase shift (in the jammer direction) between the signals from the columns of modules in the receive mode. By the proposed method, the jamming signal can be suppressed in both the transmit mode and the receive mode. The antenna gain loss in the target direction, distortion of the pattern shape, and behavior of the direction-finding characteristic have been investigated as functions of the angle of arrival of the jamming signal and of the selection of antiphased columns of the phased-array antenna (PAA). It has been observed that, when the jamming signal is suppressed in the selected azimuthal direction, a null slot extending over the entire investigated interval of elevation angles is formed. A method is proposed for determining the jammer direction from the observed response of the phase of the received signal to the antiphase conditions of the columns of modules successively generated at various angular directions (starting from the direction of the radiation-pattern maximum). The effect of the amplitude and phase deviations from the uniform amplitude and linear phase distributions of the field in the antenna aperture on all the above-mentioned parameters is investigated. All calculations have been performed for the PAAs with the quads of modules connected to separate receivers, whose output signals are digitized. With the use of a beam-forming network, the sum and difference signals are formed at its three outputs. It is shown that these signals can be easily converted to the signals from the columns and rows of the quads of modules.