关键词: 单馈点, 低剖面, 双频带, 圆极化

Abstract:

In order to reduce the profile of the multi-layer structure and the complexity of the power dividing network of the dual-frequency dual-fed circular polarized (CP) antenna, a dual-band circularly polarized microstrip antenna is designed with a single-fed single-layer structure. It has two types of pattern of omnidirectional circular polarization and broadside circular polarization in two operating bands. A combination of an Alford loop and a shorting metallic cylinder loaded in the center of the patch is uesd to excite omnidirectional circular polarization in the low operating band; and a circular patch with a pair of symmetric rectangular slots is adopted to obtain circular polarization in the high operating band. The antenna prototype is fabricated and measured. Measured results show that the designed antenna has impedance bandwidths of 75％ (242～261GHz) and 103％ (332～368GHz) (reflection coefficient<-10dB). Axial ratio (AR) bandwidths are 4％ (244～254GHz) and 23％ (346～354GHz) (AR<3dB), respectively. The gain variations within two operating bands are less than 04dB. This antenna can be applied to the 25／35GHz frequency band of Worldwide Interoperability for the Microwave Access (WiMAX) system.

Key words: single-fed, low-profile, dual-band, circular polarization