Dual-band circularly polarized antenna with differential feeding

Abstract

A dual-band circularly polarized antenna is presented in this paper. A rectangular patch antenna with gap-feeding structure is firstly designed, and 3-dB axial-ratio bandwidth from 2.35 to 2.48 GHz is obtained. A parasitic square ring is placed on the rear of the rectangular patch as a band-notch unit operating around 2.4 GHz. Then an original wide circularly polarized band is split into two bands from 2.25 to 2.31 GHz and from 2.46 to 2.53 GHz. By adopting differential feeding, symmetrical patterns are achieved. Measurement results show that two 3-dB axial-ratio bands of 2.6% (2.25-2.31 GHz) and 2.0% (2.51-2.56 GHz) are obtained with a small frequency ratio of 1.11.