A small frequency ratio dual-band circularly polarized microstrip antenna

A compact single-feed dual-band circularly polarized (CP) patch antenna with small frequency ratio is presented. The proposed antenna consists of a circular patch and a narrow annular-ring, which resonate at 1.70 GHz and 1.57 GHz for respectively. The annular-ring was involved to obtain dual band characteristic. The CP operation is achieved by an unequal cross-slot embedded in the circular patch. Simulated and measured results are presented and discussed.