Advances on time-modulated arrays for cognitive radio

In time-modulated arrays (TMAs), the fourth dimension, time, is exploited to synthesize antenna systems characterized by unconventional operational features that make them attractive for next generation communication systems based on Cognitive Radio. The possibility to synthesize TMAs able to generate multiple beams, suitable in multiple-input multiple-out (MIMO) systems, and to transmit the information in a correct manner only along some particular directions are discussed in this paper with main emphasis on the first problem. These features are obtained by simply reconfiguring the on-off control of a set of radio-frequency switches used in the beamforming network to modulate the static excitation weights.