PLANAR ENDFIRE CIRCULARLY POLARIZED QUASI-YAGI ANTENNA WITH ENHANCED BANDWIDTH AND REDUCED SIZE FOR WIDEBAND WIRELESS APPLICATIONS

A planar endfire circularly polarized quasi-Yagi antenna with the feasibility of obtaining a wider bandwidth and relatively smaller size is proposed and demonstrated. With a planar double-sided printed complementary structure, the proposed endfire circularly polarized (CP) antenna, consisting of a vertically polarized planar quasi-Yagi array and a horizontally polarized planar quasi-Yagi array with a common driver, is designed, analyzed, and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed antenna can provide an impedance bandwidth of 16.3% (5.02–5.91 GHz) and a 3 dB axial ratio (AR) bandwidth of 17.4% (5–5.95 GHz). Meanwhile, the proposed antenna has endfire gains from 5.4 dBic to 7.4 dBic with an average endfire gain of 6.3 dBic, and front-to-back (F/B) ratios ranging from 10.2 dB to 16 dB with an average F/B ratio of 11.9 dB. Additionally, the measured effective CP bandwidth of 16.3% (5.02–5.91 GHz) not only meets the need for certain Wi-Fi (5.2/5.8 GHz) or WiMAX (5.5 GHz) band communication application, but also provides the potential to implement multiservice transmission.