单馈点低剖面双频带圆极化天线

Single-fed low-profile dual-band circularly polarized antenna

为了解决双频双馈圆极化天线叠层结构剖面高及功分网络复杂的问题,设计了一种采用单馈点单层微带形式实现双频带圆极化特性的天线.该天线具有低频全向圆极化和高频边射圆极化两种方向图.低频全向圆极化通过奥尔福德环和加载在贴片中心的金属短路柱组合实现;高频边射圆极化利用开矩形槽的圆形贴片产生.对设计的双频带圆极化天线进行了加工及测试,测试结果表明,在两个工作频段内,天线阻抗带宽分别为7.5%(2.42~2.61GHz)和10.3%(3.32~3.68GHz),反射系数小于-10dB;轴比带宽分别为4%(2.44~2.54GHz)和2.3%(3.46~3.54GHz),轴比小于3dB.两个工作频带内增益起伏小于0.4dB.此天线可应用于全球微波互联接入系统的2.5/3.5GHz工作频段.

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%(2.42~2.61 GHz)and 10.3%(3.32~3.68 GHz)(reflection coefficient<-10 dB).Axial ratio(AR)bandwidths are 4%(2.44~2.54 GHz)and 2.3%(3.46~3.54 GHz)(AR<3 dB),respectively.The gain variations within two operating bands are less than 0.4 dB.This antenna can be applied to the 2.5/3.5 GHz frequency band of Worldwide Interoperability for the Microwave Access(WiMAX)system.