International Journal of Advancements in Electronics and Electrical Engineering
Author(s) : AAMIR AHMAD , ANANDA KUMAR BEHERA , G. K. MAHANTI , ROWDRA GHATAK , S. K. MANDAL
In this paper, the additional dimension ‘time’ is used to synthesize cosecant squared shaped, beam pattern in linear antenna arrays with digitally controlled static amplitude and the phase shift of the array elements. The static amplitude and the phase shift are assumed to be obtained from the output of a five bit digital converter. For the desired shaped beam pattern, normalized on-time duration and the quantized value of the static amplitudes and phase shift are obtained by using Differential evolution (DE) algorithm. The search space of the static amplitudes, phase shift and switch on-time durations are considered as (0.05, 1), (0, 2π) and (0.04, 1) respectively. Thus with relatively low dynamic range ratio of static amplitude and sufficiently high value of on-time duration, the feed network of the antenna array can be designed easily. The proposed approach is demonstrated with a 30 element time modulated linear antenna array (TMLAA) by synthesizing the shaped beam pattern for the angular beam width of 300 and reducing the maximum side lobe level (SLLmax) and sideband level (SBLmax) to -22.92 dB and -27.29 respectively.