Time-modulated array design for new generation communication systems

Time modulated arrays (TMA) use radio-frequency (RF) switches to modulate in time the static excitation weights of an ordinary phased array to shape the antenna radiation diagram. The on-off commutation of the switches, which are controlled by means of a periodic pulse sequence, generates harmonics that are spaced in frequency by multiple of the pulse repetition frequency. These harmonics, whether filtered, represent a power loss that unavoidably reduces the directivity at the antenna operating frequency. Differently, in this work the harmonics are suitably exploited and the pulse sequence controlling the RF switches is optimized to design an antenna able to generate multiple harmonic beams pointing at different directions in order to independently receive the signals that are incident on the array. Representative numerical examples are reported to validate the effectiveness of the approach.