Novel Low-loss Coaxial Slot Array Based on Gap Waveguide Technology for E-band Automotive Radar Applications

This paper presents a novel ultra-thin slotted array antenna for automotive radar applications operating at E-band. A low-loss air-filled coaxial waveguide transmission line based on multilayer waveguide (MLW) technology is formed by vertically stacking three unconnected thin metal plates. The proposed antenna element consists of two series-fed columns of 6 slots which are combined with a power divider. In order to prevent any possible field leakage due to the air gaps between the layers, a periodic textured structure is used in the top and bottom layers. The desired patterns are fabricated by using chemical etching technique which is a fast and low-cost manufacturing process suitable for mass-production. The design, numerical simulations and experimental validation of the proposed antenna are presented in the frequency band from 76 to 81 GHz. The measurement results show a realized gain of around 15 dBi and a reflection coefficient better than -10 dB in the entire band of interest. The proposed coaxial MLW slot array antenna provides the advantages of low-loss, low-profile, low-cost and mass-production capability at millimeter-wave frequencies.