Endfire Circularly Polarized Antenna Based on Spoof Surface Plasmon Polaritons Coupled-Line

In this paper, an endfire circularly polarized (CP) antenna is proposed and designed based on spoof surface plasmon polaritons coupled-line. Spoof surface plasmon polariton (SSPP) structures located on two orthogonal substrates serve as both a coupled line and a radiator. This structure provides phase quadrature and polarization orthogonality required by the circular polarization. The simulated axial ratio is stable below 3 dB and the return loss is over 15 dB from 8.8 to 9.6 GHz. Peak gain is 8.14 dBic at 9 GHz. This structure can be fed by only one coaxial connector which greatly reduces the design complexity and the space occupation of the feeding structure. This is significant especially in the circularly polarized array design.