94/237 GHz Dual-band Reflector Antenna with Equal Beamwidth for Weather Radar Applications

In this paper, a fully metallic dual-band offset-fed parabolic reflector antenna operating at 94/237 GHz bands is proposed for weather radar applications. The dual-band horn feeder consists of two waveguides, a low-pass filter, a multi-mode transition, and a set of annular corrugations. The filter is used to separate the 94/237 GHz signals. The multi-mode transition and the corrugations are adopted to generate pencil beams, which can also change the position of phase center in the two bands. In order to achieve equal beamwidth at 94 GHz and 237 GHz, the focal point of the reflector antenna is optimized, and the beamwidth at 237 GHz can be broadened. A prototype of the dual-band antenna is fabricated and measured. The measured bandwidth can cover 90.4-96.6 GHz and 220-250 GHz. The 3-dB beamwidth measured by in-house near-field platform is about 0.57° at 94 GHz, and is about 0.54° at 237 GHz. Quasi-equal beamwidth is achieved in the two frequency bands.