A Method for Reducing High-Frequency Sidelobes of a Millimeter-Wave Double-Ridged Horn Antenna

A simple method for reducing sidelobes at high-frequencies and stabilizing the 10dB-beamwidth of a wideband, 36-95 GHz millimeter-wave ridged feed horn is proposed. Specifically, the modulation of the ridges enabled by additive manufacturing is shown to lower sidelobe levels by up to 10 dB within a 15 GHz SLL reduction bandwidth. Tradeoffs between sidelobe levels, phase center, and impedance match are studied using parameterized full-wave models; the near-field, far-field and port results are all used in characterizing our antennas. A theoretical analysis of the proposed design using the sampled aperture fields (simulated) indicates that the increased phase taper and flattened amplitude distribution directly cause the sidelobe reduction and beamwidth broadening. Measured far-field results agree well with theory, validating the robustness of the proposed approach.