Compact Low-Loss Slot Array Antenna Based on Strip-on-Substrate Coaxial Multi-Layer Waveguide for 77 GHz Automotive Radar

Journal article, 2026

A compact, ultra-thin, low-loss and low-cost slot array antenna is presented for 77-GHz automotive radar, offering high polarization purity. Using strip-on-substrate coaxial multi-layer waveguide (SCMLW) technology, the design features a linear dogbone-shaped non-tilted centrally aligned slot array fed by a meandered metallic strip of the SCMLW. The proposed coaxial line-fed slotted antenna eliminates the angular and positional offset of slot employed in earlier designs, which are known to increase cross-polarization. Four prototypes, two 1×6 and two 2×6 slot arrays, were fabricated by chemical etching on a single platform with an overall thickness of only 0.9 mm, where long slits are introduced to improve radiation patterns. Measurements over 76–81 GHz show reflection coefficients better than -10 dB and relative cross-polarization levels below -29 dB for all prototypes, confirming their suitability for millimeter-wave automotive radar applications.