A circularly polarized microstrip patch antenna with enhanced bandwidth based on substrate integrated waveguide techniques

摘要

In this article, a circularly polarized (CP) microstrip patch antenna (MPA) is proposed.The antenna adopts a substrate integrated waveguide (SIW) cavity and amicrostrip patch as the feed structure and the radiator, respectively. In consequence,the patch dominates the radiation and improves the radiation efficiency,while the asymmetric SIW cavity enhances the bandwidth and generates a pair ofdegenerate modes, which provide the quadrature phase shift that the CP radiationrequires. By this mean, the proposed antenna not only brings up a novel feedstructure for CP MPA and improves its effective bandwidth, but also circumventthe limitation of the SIW cavity slot antenna, which is low radiation efficiency.Plus, the presented antenna remains the advantages of SIW structure, includinghigh Q factor, high integrate compatibility, and so forth. The antenna was fabricatedand measured, and the presented antenna exhibits an impedance bandwidthof 12% (from 2.09 to 2.36 GHz), an axial ratio bandwidth of 7.73% (from2.15 to 2.32 GHz) with a minimum gain of 7.89 dB. The experiment results indicatea good agreement with the simulation.