A miniaturized circularly polarized microstrip antenna for GPS applications

A novel circularly polarized microstrip antenna is presented for global positioning system (GPS) applications at 1.575 GHz. The Crown Square fractal shape is utilized for microstrip antenna design. This antenna is designed on two different substrates and the effect of these substrates on the performance of microstrip antenna is studied. Simulation results of both cases show very good circular polarization characteristics with a 3-dB axial ratio bandwidth of about 0.51% and 0.38% and very wide beam-width of about 160^o and 115^o for a 3-dB axial ratio. Also voltage standing wave ratio (VSWR) bandwidth of about 2.2% and 1.4% are achieved in both cases. To validate the results, a prototype model of fractal antenna on available substrate is fabricated and its radiation patterns and VSWR are measured. A good agreement between the results is observed.