Advanced harmonic radiations design in time-modulated antenna arrays

Time-modulated arrays (TMAs) are antenna systems in which the beam-forming is achieved by properly synthesizing the periodic pulse sequence controlling the radio-frequency (RF) switches at the output of each array element. Because of the periodic pulse behavior, harmonic signals are generated at multiples of the modulation frequency which can be suitably exploited for different applications, like direction of arrival estimation, monopulse radar, and secure communications. In order to obtained the desired patterns at the desired harmonic frequencies, an optimization technique based on the pulse splitting is here proposed and the Particle Swarm Optimizer is used to define the optimal parameters of the pulse control sequence. A representative numerical result is shown to assess the performance of the proposed method.