Efficient Sideband Suppression in 4-D Antenna Arrays Through Multiple Time Modulation Frequencies

A novel approach, named multiple time modulation frequency, is proposed for the effective suppression of the sideband radiations in 4-D antenna arrays. The time modulation frequency, different for each array element, is exploited as additional design parameter to avoid the superposition of the sideband frequencies generated by the array elements. A customized optimization strategy including the analysis of the mutual coupling effects among the array elements is proposed for the 4-D array synthesis. Selected numerical and experimental results are provided to show that the sideband level of a 4-D antenna array can be significantly reduced by properly designing the switch-on time intervals of each element, even with uniform amplitude excitations.