Periodic Substrate Integrated Waveguide Leaky-Wave Antenna with High Scanning Rate at 77 GHz for Automotive Radar

A diplexer-based periodic substrate integrated waveguide (SIW) leaky-wave antenna (LWA) operating in the 77 GHz automotive radar band is presented. Unlike conventional periodic LWAs that require wide operating bandwidths to achieve large beam-scanning ranges, the proposed architecture distributes the beam-scanning functionality across multiple frequency-selective radiating arms, thereby enabling wideangle beam steering within the limited bandwidth allocated to automotive radar systems. The antenna employs three radiating arms that are selectively excited through a frequency-dependent routing network, producing beam directions of approximately - 26° to -30°, 0°, and 26° to +30° over the 77-81 GHz band. The proposed SIW LWA provides a compact, low-complexity, and high-scanning-rate solution well suited for millimeter-wave automotive radar proximity detection applications.