Skew-grid dichroic plate with rectangular apertures for use on a Ka-Band beam waveguide antenna

The first Ka-Band Deep Space Network downlink demonstration was recently carried out by the Ka-Band Link Experiment (KABLE) in association with the Mars Observer spacecraft. In order to support the mission, a dichroic plate was required in the DSS-13 beam waveguide antenna to allow simultaneous X- and Ka-Band dual-frequency operation. AnX/Ka/KABLE dichroic plate was designed to transmit a future Ka-Band downlink (31.8–32.3 GHz), future Ka-Band uplink (34.2–34.7 GHz), and KABLE downlink frequency (33.6–33.8 GHz), while reflecting X-band (7.1–8.6 GHz). A computer program was developed for the analysis of a dichroic plate with rectangular apertures using the mode-matching method. The plate was then fabricated and tested. The reflection, group delay, and noise temperature in the antenna system due to the dichroic plate were measured. The experimental results show good agreement with theoretical predictions.