Multibeam steered pattern synthesis in time-modulated antenna array with controlled harmonic radiation

This article deals with the synthesis of multibeam steerable patterns in time-modulated arrays (TMAs) for electronic scanning. The simultaneous generation of multiple beams in TMAs can be achieved through the exploitation of undesired harmonic radiations emitted at the multiples of modulating frequency due to the periodic switching. The direction-dependent harmonic beams are capable of producing independent information channels with different spatial distributions beneficial for electronic beam steering. Multibeam patterns associated with harmonic frequencies along with the fundamental pattern can be synthesized with suitably designed switching schemes. The potentialities of linear TMAs are explored in this article to generate a simultaneous sum and difference pattern useful for monopulse tracking systems. Further assessment of multipattern operations with linear TMAs are proposed with beam steering at lower-order harmonics. Steered double sum pattern with controlled harmonic radiations are also generated to achieve a steered multibeam with simplified beamforming network. Towards this aim, both the analytical and the optimized solutions of periodic switching sequences for different multibeam patterns are developed. Modified differential evolution with a wavelet-based mutation strategy (DEWM) is employed for the optimal solution. Representative results are assessed and compared with other published literature results to show the effectiveness of the proposed methods.