Dual Frequency Feed Horn Design for a Compact Cloud and Precipitation Radar Operating at Ka- and W-band

We present the design of a compact dual frequency feed horn optimized to operate at Ka-band (35.75 GHz) and W-band (94.05 GHz). The feed horn consists of a single spline profile horn along with a diplexer having orthogonal Ka- and W-band ports and a band pass filter at the Ka-band port. The filter is used to achieve high isolation between the Ka- and W-band ports. A directivity of 21 dB and - 12 dB beam width of 31 degrees was achieved at Ka-band and a directivity of 26 dB and -12 dB beam width of 21 degrees was achieved at W-band. The overall feed horn assembly is compact and easy to machine. The dual frequency horn will be tested as part of a Ka/W-band breadboard radar.