Bandwidth Improvement of Single-Layer, Circularly-Polarized, Proximity-Fed Patch Antenna

This paper presents a single-layer circularly polarized (CP) proximity-fed patch antenna with bandwidth improvement. The design consists of four rectangular patches, which are fed by a common 50-Ω microstrip line with open-ended termination through proximity coupling. By using both capacitive and inductive coupling mechanisms and carefully optimizing the positions and sizes of the rectangular patches, the antenna yields multiple resonances and minimum axial ratio (AR) points. By merging these resonances, the bandwidth is significantly enhanced. The final design yields a |S
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| < -10 dB bandwidth of 16.96% (8.27 - 9.81 GHz) and AR ≤ 3-dB bandwidth of 6% (8.89 - 9.44 GHz), the peak gain of 9.94 dBic, and radiation efficiency of ≥83%.