Novel Single-feed Proximity Coupled Wideband Circularly Polarized Slot Antenna

A wide impedance and axial ratio bandwidth single-feed method for circular polarized slot antenna is proposed. Impedance and axial ratio bandwidth of approximately 20% have been achieved. The circularly polarized antenna operates at its fundamental TM(11) mode is fed by a simple U-shaped microstrip line structure through proximity coupling. Two 100 Q impedance transformers have been used to align the impedance and axial ratio bandwidths. Simulations show that the source current, which flows in the annular section of the U-shaped feed, induces a circulating current in the circular slot radiator which contribute the circular polarized radiation. Both currents flow in the same direction. Experimental and simulation results of the antennas are presented and discussed.