Dual-Band Circularly Polarized Antenna Combining Slot and Microstrip Modes for GPS With HIS Ground Plane

A dual-band circularly polarized antenna for GPS L1 and L2 bands is proposed and investigated in this letter. The dual-band design is realized based on the strategy of combining the microstrip mode and annular slot mode. The proposed antenna consists of an annular slot radiator printed on a square substrate and a high impedance surface (HIS) ground plane. The HIS, working as ground plane for microstrip mode and reflector for slot mode radiation, is settled under the square substrate to realize unidirectional radiation with low profile. Experimental results show that the proposed antenna exhibits two overlapped impedance and axial ratio bandwidth of 40 MHz (1.210-1.250 GHz) and 50 MHz (1.555-1.605 GHz) and the measured gains are about 8.0 dBic and 7.5 dBic, respectively. Very low backward radiation can also be observed in both operating bands.