Partially-Filled Half-Mode Substrate Integrated Waveguide Leaky-Wave Antenna for 24-GHz Automotive Radar

A novel highly efficient leaky-wave antenna (LWA), based on a periodic set of holes created in a half-mode substrate integrated waveguide (SIW), is conceived for automotive radar. The computer-aided design of this partially-filled SIW (PFSIW) LWA is carried out using a full-wave electromagnetic simulator. As a proof-of-concept, an LWA prototype having a plate size of 15x126 mm2 is fabricated through a standard low-cost printed circuit board (PCB) manufacturing process. Our manufactured prototype yields more than 25% impedance bandwidth, targeting the 24 GHz automotive short-range-radar band. Moreover, the measured peak gain and total antenna efficiency reach up to 15.5 dBi and 85% at 24 GHz. Furthermore, the main radiating direction steers continuously from 38° to 58° with an average half-power beamwidth of 12° when the operating frequency changes from 22 GHz to 26 GHz. In comparison, a 160-mm-long dielectric-filled SIW LWA yields a measured scanning range of 49° and a total antenna efficiency of 43.8%, whereas an 80.3-mm-long air-filled SIW LWA exhibits a measured scanning range of 9° and a total antenna efficiency of 80%. Therefore, PFSIW technology provides an optimal trade-off between DFSIW and AFSIW for the envisaged short-range automotive radar application.