Broadband circularly polarized patch antenna for small satellites applications

A novel broadband circularly polarized annular patch antenna is presented in this paper. The antenna consists of two annular ring patches which serve as an excitation patch and a parasitic patch, respectively. To produce circular polarization, small perturbations in the shape of triangles are loaded on the patches. To validate the concept, a prototype antenna at S band is designed and fabricated. The measured results confirm the antenna is able to achieve good impedance match and low axial ratio values over a wide range of frequencies. The simulated results agree well with measured results, which show an impedance bandwidth (S11<-10dB) of 19.5%, and an axial ratio bandwidth (AR<3dB) of 10.9%. The antenna has a compact size and low cost, thus useful for small satellite data downlink and Telemetry Tracking and Command (TTC) applications.