Design of a High-Isolation 35/94-GHz Dual-Frequency Orthogonal-Polarization Cassegrain Antenna

In this letter, a novel high-isolation 35/94-GHz dual-frequency orthogonal Cassegrain antenna is designed. The antenna consists of a D = 800 mm main reflector, a subreflector, and a dual-band orthogonal-polarization feed. In order to get similar feed horn's E-H radiation patterns and similar phase center positions at the dual frequencies separately, the dual-mode conical horn is designed in the feed. For obtaining a high isolation, a three-order low-pass filter is designed in the Ka-band waveguide feed port. The measured antenna gains are 43.6 and 51.3 dBi, and the sidelobe levels are -27.5 and -26.5 dB at 35 and 94 GHz, respectively. The isolation between the two ports is -61.0 dB in the Ka-band and -63.5 dB in the W-band. The proposed antenna is a suitable candidate for a dual-band radar system.