A Broadband E-Band Single-Layer-SIW-to-Waveguide Transition for Automotive Radar

An $E$ -band air-filled rectangular waveguide (RWG) to single thin-layer (0.127 mm) substrate integrated waveguide (SIW) transition is proposed for automotive radar applications. The compact transition structure is realized using a symmetric narrow aperture coupled comb patches. With the mutual coupling effect between patches, a bandwidth greater than 22% for $|S_{11}| < -15$ dB is achieved. A back-to-back prototype is fabricated and measured. The results show that the insertion loss of a single transition is less than 0.5 dB within 71–86 GHz, which covers the whole attractive frequency range for automotive radar. With broadband and compact size, the proposed transition presents potential for automotive radar.