Harmonic beam reconfigurations using particle swarm optimization in time modulated arrays

Time-modulation (TM) arrays is implemented by using a set of radio-frequency switches in the beam forming network to modulate, by means of periodic pulse sequences to control the antenna radiation features. The on–off reconfiguration of the switches that can be easily implemented via software unavoidably generates harmonic radiations that can be suitably exploited for multiple channel communication purposes. An innovative approach to the design of time-modulated arrays able to generate multiple and simultaneous harmonic beam patterns pointing towards different directions is presented. In time modulated arrays, because of the introduction of the periodic time modulation, multiple harmonic signals are generated. The synthesis of the pulse sequence controlling the RF switches is performed by means of a Particle Swarm Optimizer (PSO) to generate multiple harmonic beams able to simultaneously receive multiple signals arriving on the antenna from different directions. Towards this aim and in order to independently receive a signal on each harmonic channel generated by the receiving time-modulated array each harmonic beam has to be optimized such to have a maximum towards the DoF of one arriving signal and deep side lobes or nulls along the directions of other signals.