Multi-beam steered harmonic pattern synthesis in timed antenna array with optimized and pre-defined RF switching

摘要

Optimal harmonic beam steering of the time-modulated linear antenna array (TMLAA) with optimized and pre-defined ON and OFF switching schemes are proposed in this work. Three different approaches are considered to obtain various beam steering behaviors of TMLAA. The first approach is considered for the optimization of ON-OFF switching sequence for the steering of the harmonic beams toward approximately +/- 30 degrees along with the simultaneous reduction of side lobe level (SLL) and side band level (SBL). Second approach is considered for the optimization of ON-OFF switching sequence for the steering of the harmonic beams toward approximately +/- 30 degrees and +/- 60 degrees simultaneously. Third approach is considered for the optimal reduction of SLL and SBL of harmonically steered beams for a pre-defined ON-OFF switching scheme. Two unique cost function is proposed in this work to achieve the optimal parameter for above mentioned three different approaches. The first cost function is used for the optimization of T-on and T-off switching sequence and antenna element spacing of the array. These optimal values will lead to steer the main beam of first positive and negative harmonic radiation from the main beam of the fundamental radiation pattern and reduce SLL and SBL simultaneously. Second cost function deals with the optimization of excitation amplitude and distance between any two consecutive antennas of the array. These optimal values lead to reducing the SLL and SBL simultaneously harmonically steered beam obtained by pre-defined T-on and T-off switching sequence. Optimization algorithm applied to get the optimal value of the variable parameters is Novel Particle Swarm Optimization. Further to explain the stated proposed approach, four different sets of 10-, 16-, 20-, 32-element TMLAA are taken as an example. Some of the simulation results are validated through electromagnetic simulator to validate the result obtained by MATLAB.