Improvement in various radiation characteristics of time modulated linear antenna arrays using evolutionary algorithms

Abstract

In this paper the authors propose the optimal radiation pattern synthesis of time modulated linear isotropic antenna array with improved directivity and maximum reduction of side lobe level (SLL) and minimum side band levels (SBL) at its harmonics based on evolutionary algorithms applied individually. Evolutionary algorithms are real coded genetic algorithm (RGA), particle swarm optimisation (PSO), novel particle swarm optimisation (NPSO), and the fourth dimension parameter as time. The same array radiates at various harmonic frequencies. The first two harmonic frequencies have been considered in this work. The objective function judiciously chosen enables comparative performance evaluation of the case studies. The numerical results show Case-4 outperforms Case-1, Case-2, and Case-3 with respect to better side lobe level and more improved directivity. Again, the performance of NPSOWM is the best among RGA, PSO, and NPSO for all the case studies. The numerical results also show power radiated by any harmonic frequency is very less as compared to the power radiated at centre frequency called fundamental frequency. It has also been observed that as the harmonic frequency increases, sometimes SBL increases as compared to SLL but powers radiated by the antenna at its harmonic frequencies decrease. As per authors knowledge there is no contribution by any other previous researcher regarding numerical computation of powers radiated at fundamental frequency and its two harmonic frequencies, dynamic efficiency and directivity for time modulated linear antenna arrays.