Dual-Band Circularly Polarized Annular Slot Antenna With a Lumped Inductor for GPS Application

A dual-band circularly polarized antenna with a lumped element for global positioning system (GPS) applications is proposed and analyzed in this communication. The proposed antenna mainly consists of a square patch with an annular-ring slot, an inductor, and a metallic reflector. The square patch with the annular-ring slot is excited by a T-shaped microstrip line. This produces the left-handed circular polarization (LHCP) in the GPS L1 (1.563-1.587 GHz) and L2 (1.215-1.240 GHz) bands with the help of the inductor and the metallic reflector. In addition, the antenna with the reflector exhibits a unidirectional radiation in both operating bands. A prototype of the antenna is fabricated and measured to verify the simulation results. The measured results show a wide -10 dB reflection coefficient bandwidth of 40.57% (1.12-1.69 GHz) and 3 dB axial ratio bandwidths of 6.56% (1.18-1.26 GHz) and 7.74% (1.49-1.61 GHz) in the lower and higher bands, respectively. LHCP gains of 7.72 and 8.11 dBic are also observed at 1.227 and 1.575 GHz, respectively.