Abstract

In the framework of the synthesis of time-modulated array antennas for communication purposes, the thesis focuses on the analysis and the development of innovative approaches aimed at reducing the power losses related with the undesired harmonic radiations. The accurate analysis of the problem in hand has been used to identify the fundamental parameters involved in the waste of power when the elements of the array are modulated using RF switches. The sideband radiations have been firstly indirectly handled throughout the reduction of the sideband levels of the patterns of the harmonics by means of the minimization of a suitable cost function using a stochastic optimizer, the Particle Swarm Optimizer. Successively, by exploiting a closed form relationship describing the total power wasted in sideband radiations a new synthesis method has been developed allowing a significant reduction of the computation effort and a more effective dealing with the synthesis problem. Moreover, a careful study of the potentialities and the applications of such methods in others antenna synthesis problem has been carried out referring in particular to the reduction of the sideband radiations in monopulse array antennas in which the difference pattern is obtained by means of sub-arrayed feed network. In the numerical validation, a set of representative examples concerned with the reduction of the sideband levels and the power of the harmonic radiations are reported in order to assess the effectiveness and the flexibility of the proposed approach. Comparison with previously published results are reported and discussed, as well.