Compact, Broadband, and Highly Efficient Leaky-Wave Antenna in Air-Filled Substrate Integrated Waveguide Technology

A highly-efficient multilayer half-mode air-filled substrate integrated waveguide (HM-AFSIW) leaky-wave antenna (LWA) is demonstrated for millimeter-wave automotive radar systems. The antenna consists of two main parts: the antenna feed and a leaky-wave-based radiating part. The antenna feed is implemented in a single layer high-performance 0.5-mm-thick Rogers 4350B substrate. In the radiating part, two 1-mm-thick FR4 substrates sandwich a Rogers 4350B substrate, realizing an air-filled region. The antenna concept has been validated by measurements in the [22-26] GHz band, exhibiting a scanning capability over 9 degrees in the elevation plane thanks to the frequency scanning behavior of the leaky-wave radiating part. The developed antenna is well-suited for fabrication by single-layer low-cost printed circuit board processes, and its low profile and compactness can be considered as a promising solution for automotive radar applications. The yz-plane radiation patterns measured in the [22-26]-GHz band show an average half-power beamwidth of about 12 degrees and sidelobe levels better than 18 dB. The measured peak gain at 24 GHz equals 15 dBi, resulting in a total efficiency higher than 80%.