A. O. Manichev

Noise immunity is one of the most important requirements on modern radio-enginering systems (RES). Synthesis of pattern nulls of the phased array antenna (PAA) installed in a RES is an efficient way for enhancement of noise immunity. Phase-only synthesis methods are of special interest because they involve only software changes and do not require any additional equipment. In real PAAs, random distortions of the amplitude-phase distribution are always present. These distortions limit the depth of formed nulls to a certain background level. Recently, new efficient methods for synthesis of deeper nulls were proposed. These methods include measurement of the values of the complex PAA pattern in the directions of synthesized nulls and use of the measured values as the initial point for the univariate phase-only synthesis method. Recently, the efficiency of these methods was experimentally verified. However, optimization of the parameters of the univariate method used for solving this problem was not yet discussed. This paper considers two issues: (1) determination of the optimum value of the normalization constant for the element excitation amplitudes used in the univariate algorithm and (2) determination of the optimum element selection order for a PAA with arbitrary amplitude distribution. The first issue deals with the influence of measurement uncertainties and random phase distortions of PAA element excitations on the average values of the initial pattern and complex excitations of the PAA elements. These factors affect the average amplitudes of the PAA element excitations. Therefore, an analytical expression for the optimum value of the amplitude normalization constant is determined in order to minimize the adverse effects of random distortions. The second factor affecting the null depth is that the following two conditions must be met simultaneously: 1) The number of PAA elements used in the null synthesis procedure should be as small as possible; 2) The squared amplitudes (powers) of the excitations of the elements used for synthesis should be as small as possible too. In order to satisfy the two contradictory conditions, a new element selection order in the phase-only univariate algorithm is proposed. The efficiency of the proposed measures was verified via computer simulation.