Wideband Untilted Narrow Wall Slotted Partially Staggered Waveguide Array Based on Metallized Molded Plastic at E-Band

A slotted waveguide antenna for automotive multiple-input-multiple-ouput (MIMO) radar at 76-81 GHz consisting of a linear array with radiating untilted slots in the waveguide narrow wall is presented. Novel electrically large shared protrusions (>lambda(0)/2) in the waveguide walls to perturb transversal currents for high polarization purity while holding TE10 transmission properties and maintaining manufacturing constraints for millimeter-wave high-volume production are proposed. The design consists of only two layers of metallized plastic fabricated with injection molding, physical vapor deposition, electroplating, and soldering processes. Details about design methodology, electromagnetic simulations, and manufacturing process are disclosed. Prototyping confirms the feasibility of the proposed antenna concept at E-band and its outstanding performance with an impedance bandwidth above 13.1%, 90% (-0.5 dB) of total efficiency at 78.5 GHz and a high cross-polar discrimination (28 dB).