Circularly polarized antenna array fed by spoof surface plasmon polariton waves

A two dimensional circularly polarized (CP) patch array antenna with compact size operating in Ku band is proposed in this paper. To excite the antenna array, a novel spoof surface plasmon polaritions transmission line (SSPPTL) is used and mounted vertically on the ground. The SSPPTL is excited by a waveguide with a horn and a gradient transition for the momentum and impedance matching. Four SSPPTLs form a 4-way power divider to feed the 4×7 circular patch array. Fed by the travelling waves on the SSPPTLs, the CP radiation is generated on the patches, which is located between SSPPTLs. Avoiding the deterioration in axial ratio, 90° phase difference between adjacent SSPPTLs is fixed by tuning the height of the SSPPTLs, since the property of the dispersion is influenced by the height obviously. In the simulation, a maximum gain of 21.2dBi is achieved at 15.3GHz, together with the axial ratio of 0.43dB. A prototype is fabricated and measured to validate the proposed antenna array.