A single-feed K-Band patch antenna featuring circular polarization is presented. The proposed star-slot-coupling structure offers both polarization and input impedance adjustment capability. In combination with a truncated radiating element high-purity polarization is achievable at the operating frequency. Simulation shows that an axial ratio (AR) as low as 0.05 dB can be achieved. The design is robust against fabrication tolerances. Measurement results of a left handed circularly polarized (LHCP) antenna are presented. They show good agreement with simulation. Typically, the bandwidth reaches 10% for 10 dB matching and 4% for 6 dB axial ratio.
