Application of Time-Modulation to Design Low Sidelobe Phase-Differentiated Dual-Beam Linear Antenna Arrays with Low DRR

In this paper, the additional flexibility in designing antenna arrays by employing time-modulation (TM) technique have been exploited to synthesize phase-differentiated dual beam patterns with low dynamic range ratio (DRR) of static excitation amplitude. An optimization technique based on differential evolution (DE) is utilized to find out a common set of static amplitude and switch-on time (SOT) distribution that generates two different patterns when only, appropriate phase distributions of the corresponding patterns are altered suitably. In order to show the effectiveness of the proposed approach, two different set of beam pairs namely flat-top / flattop (FT/FT) and pencil beam / flat-top (PB/FT) are considered. For a 20 element time-modulated linear antenna array (TMLAA), all the patterns are realized by suppressing side lobe level (SLL) to -30 dB while the static excitation amplitude is perturbed in the search range (0.25 - 1) so as to limit DRR ≤ 4. Sideband levels (SBLs) of the unwanted sideband radiation that appeared due to periodical commutation of the switches connected to the antenna elements are also suppressed to significantly low value.