在研究磁探针耦合特性的基础上,设计了中心频率为4.0 GHz的3圈36单元高功率单层径向线螺旋阵列天线,各圈距中心位置分别为45,90,135 mm,单元个数分别为6,12,18.该天线采用磁探针代替电探针给短螺旋单元天线馈电,通过同轴-径向线模式转换器实现径向线TEM外行波激励,采用调整磁探针的探入深度和绕轴旋转短螺旋单元天线的方法改变单元的激励幅度与激励相位.数值模拟结果表明:该口径为324 mm的天线在中心频率上可获得21.58 dB的增益,口径效率可达78.2%,轴向轴比值为1.73;在3.8～4.2 GHz的频率范围内增益大于20.85 dB,口径效率大于73.2%,轴向轴比值小于2.0,反射系数小于0.27,辐射效率大于93%.

Helical array antenna is fed from a single-layered radial waveguide to realize the directional radiation of high-power microwave.Low-profile helix is used as a radiation element.The feed wire of each helix is connected with an H-coupled probe,and excited by an outgoing wave in the TEM mode between the two parallel plates of the radial waveguide.Helices and probes are arranged on the upper plate to form a circular array.The excitation amplitude and phase of each element are adjusted by changing the insert length of H-coupled probe and rotating low-profile helix respectively.This antenna accepts directly an azimuthally symmetric output of an HPM source and radiates a high-gain pattern with a boresight peak.H-coupled probes are used to make the array antenna compatible with the intense electric fields associated with high-power microwave sources.In addition,the array antenna has a simple structure and can project circular polarized electric field.An array antenna composed of 36 elements for a frequency band of 3.8GHz to 4.2GHz is designed and similated.At 4.0GHz the calculated aperture efficiency reaches 78.2% nad the axial ratio at the normal direction is 1.73.In the range of 3.8GHz to 4.2 GHz,the aperture effciency is over 73.2%,the axial ratio is below 2.0,the reflectance is less than 0.28,and the radiation efficency is more than 93%.