Design of digitally controlled multiple-pattern time-modulated antenna arrays with phase-only difference

Abstract

An optimization approach based on differential evolution (DE) is proposed to design multiple-pattern time-modulated linear antenna arrays (TMLAAs) with phase-only control by using 5-bit digital phase shifters. The synthesized multiple patterns include a pencil beam (PB), a flat-topped beam (FTB), and a cosec squared pattern (CSP). The function of the DE is to find, simultaneously, a common, i.e., fixed, set of continuous values of switch-on time durations and discrete static excitation amplitudes for 5-bit digital attenuators, and different sets of discrete excitation phase distributions for 5-bit digital phase shifters; to generate different power patterns in the far field of the TMLAA. By perturbing the static amplitude distribution of a 20-element TMLAA in the discrete search range of “(0.2–1),” the patterns are obtained by reducing side lobe levels (SLLs) to almost −20 dB and sideband levels (SBLs) to less than −25 dB. Towards the end, the same on-time and amplitude distribution is used to produce a symmetric side lobe (S-SL) and asymmetric side lobe (A-SL) CSP, and their usefulness under a noisy signal environment is discussed.