Circularly Polarized Endfire Antenna Based On Sequentially Rotated Phase-Transforming Corrugated Goubau Lines

A circularly polarized (CP) endfire antenna is proposed and designed based on the sequentially rotated corrugated Goubau lines. The open-ended corrugated Goubau lines serve as endfire radiators, and simultaneously realize phase transforming function for phase control. A pair of corrugated Goubau lines could be etched on two edges of a common metal strip, and four corrugated Goubau lines with different corrugations along two perpendicular metal strips provide sequentially rotated radiated fields, establishing the CP radiation. Complexity and space occupation of the feeding structure could be reduced by applying the phase-transforming element radiators, which is significant especially in array design. A prototype antenna is fabricated and measured to verify the design. The measured axial ratio is below 3 dB and the return loss is over 15 dB from 8.9 to 9.5 GHz. Peak gain is 8.6 dBic and the cross-polarization level is around -20 dB at 9 GHz.