A Novel Planar Dual Circularly Polarized Endfire Antenna

In this paper, a novel planar dual circularly polarized (CP) endfire antenna composed of a magnetic dipole Yagi element (MDYE) and electric dipole Yagi element (EDYE) is presented for 5.8-GHz WLAN application. Two orthogonal components E
_x
and E
_y
are provided by the EDYE and MDYE. By adjusting the amplitude of each component, the CP radiation is formed. Besides, a hybrid network composed of microstrip lines and parallel strip lines is used to excite MDYE. Dual circular polarization can be achieved by a simple and feasible 90ř directional coupler to control the radiation mode with no need of complex feeding structure. Moreover, the parameters of the proposed antenna are studied and the antenna is fabricated and measured. The theoretical design method has been numerically verified and experimentally validated. The simulation and measurement results show that the impedance bandwidth (|S
₁₁
| <; -10dB) is 170 MHz (5710-5880 MHz) and 175 MHz (5715-5890MHz) at two feed ports. Besides, good radiation characteristics with the peak gains of 5.3 and 5.2 dBic can be obtained with an 18-dB front-to-back ratio (FTBR) at its resonance frequency. The simulated and measured results show that the standard PCB process is a reliable method for antenna fabrication.