Center-Feed Post-Wall Waveguide Series-Feed Sidelobe-Suppression Slot Subarray for Millimeter-Wave Radar

We design a center-feed post-wall waveguide slot subarray of 25 radiating elements that suppresses E-plane sidelobes below -18 dB for the 76.5 GHz band (76.0 GHz to 77.0 GHz). First, by adjusting the dimension of the feeding aperture, the feeding part is designed to suppress reflection. Then, the slot lengths and post positions are adjusted, and the radiating elements are designed so that the excitation distribution calculated from the Taylor distribution is obtained. The overall structure is analyzed by combining the radiating part, in which the radiating elements are arranged so that their excitation phase distribution is uniform, and the feeding part. A prototype is fabricated and measured based on the design. The reflection is below -10 dB in a range of 74.1 GHz to 76.4 GHz for the calculated value and 74.5 GHz to 76.5 GHz for the experimental value. The sidelobe levels are sufficiently suppressed below -18 dB from 76.0 GHz to 76.6 GHz in both analysis and experiment.