Design of a time-modulator to synthesize different patterns in time-modulated antenna arrays

This paper presents a novel technique to design a time-modulator that can be used as a discrete component to generate different patterns in time-modulated antenna array (TMAA) system. The technique quantizes the modulation period into a number of levels with equal step size between the consecutive levels and rounds off the on-time of the antenna elements to nearest quantization levels to obtain quantized on-times (QOTs) of the corresponding elements. In order to realize the time modulation technique, a representative block diagram of a time-modulator defined as “quantized time-modulator” is presented. It is shown that the effect of quantization errors on the synthesized patterns can be diminished by selecting a suitable number of quantization states by using artificial bee colony (ABC) as a global optimizer. Accordingly, two previously reported examples based on simulated annealing (SA) algorithm, optimized by using continuous search space of on-time are considered, and ABC optimized results using discrete search space of QOT are compared with those obtained by SA. Finally, a fully digitally controlled, low side lobe flat-top pattern with low dynamic range ratio of static amplitude is synthesized by considering discrete search space of QOT.