Half-Power Phase Shifter for the Design of A Wideband Circularly Polarized Antenna

This paper presents a concept of using half-power phase shifter to design a circularly polarized (CP) antenna. The half-power phase shifter is composed of an open slot and a microstrip line. By elaborately loading the open slot under the microstrip line, half-power energy is radiated and half-power energy is transmitted to the end. Interestingly, the transmission phase bandwidth obtained at the end is significantly increased owing to the loading of the open slot. By using this design method, a wideband CP antenna is developed, which is composed of a pair of wide slots and a pair of narrow slot. The narrow slot pair is loaded not only for radiation, but also for the wideband quadrature phase transmission to the wide slot pair. The developed CP was finally fabricated and measured to verify the design concept. Both the measured and simulated results show that the developed antenna can have a wide AR and impedance bandwidth from 1.95 GHz to 3.45 GHz.