Sidelobe reduction in linear microstrip arrays driven through microstrip corporate feeds

Abstract

Simulation-based optimization is demonstrated for design of broadside linear microstrip antenna arrays energized through corporate feeds. Corporate feeds that are of interest here implement non-uniform amplitude excitation while include only equal-power split T-junctions as power distributing elements. A corporate feed designed and simulated as stand-alone microstrip circuit provides required complex wave amplitude at the outputs and is well matched at the input. Embedded elements of the linear microstrip array also well matched. On the other hand, a circuit comprising the antenna array connected to the feed exhibits increased sidelobes and degraded reflection coefficient. This results from deviations of the incident wave amplitudes from their expected values at the inputs of the array elements. To reduce sidelobes and keep the reflection coefficient at an acceptable level, the entire antenna-feed circuit is optimized and validated using numerical optimization and discrete electromagnetic simulations at the high-fidelity level of description. Surrogate-based methodology is exploited to speed up the optimization process. Our approach does not introduce extra hardware complications. A case study of two twelve-element microstrip array-feed circuits explains and demonstrates our approach.