Ka频段宽带双口双模馈源设计

针对卡塞格伦天线系统对馈源的要求，设计了一种Ka频段双口双模馈源，可与X频段馈源组合成体积较小的双频段馈源。采用圆环状的和差比较器结构，降低了双频段馈源的体积，通过添加过渡阶梯、圆柱销钉与金属调配板等设计，改善了双频段馈源的性能。测试结果表明，在绝对带宽2 GHz范围内，S和口、E差口与H差口驻波比均小于2，3个端口间的隔离度均大于25 dB。测试频率的和方向图在±60°时的归一化增益均在-14~-20 dB范围内，初级归一化和方向图的对称性较理想，差方向图的零值深度均小于-25 dB，满足卡塞格伦天线对馈源设计的指标要求。

Design of a Ka-band wide band dual-aperture dual-mode feed

In order to meet the requirements of Cassegrain reflector antenna system for feed,a Ka-band dual-aperture dual-mode feed is designed in this paper,which can be constituted a dual-band feed with an X-band feed. An annular comparator structure is designed to reduce the size of dual-band feed. The transitional steps,cylindrical pins and adjustment board are used to improve the performance of dual-band feed. Test results show that the voltage standing wave ratio(VSWR) of S sum port,S difference port and H difference port are all below 2,the isolation among these three ports are all larger than 25 dB in the bandwidth of absolute 2 GHz. The normalized gain of sum patterns is between -20 dB and -14 dB at ±60°. The symmetry of primary normalized sum pattern is ideal. The zero depths of difference patterns are all below -25 dB. The test results verify that the designed feed meets the requirements of Cassegrain reflector antenna.