Multi-Beam GRIN Luneburg Lens Antenna for Millimeter-Wave Radar Sensing
Authors:
Mohammad Omid Bagheri, Veronica Leong, Justin Chow, Josh Visser, Yahia M. M. Antar, George Shaker
Abstract:
Compact millimeter-wave radar modules are attractive front ends for short-range sensing owing to their small form factor, low cost, and wide modulation bandwidth. Their embedded antennas, however, provide limited effective aperture, moderate gain, and broad fixed radiation characteristics, which constrain wide-angle sector-resolved sensing when several radar channels operate simultaneously. This paper presents a passive multi-beam tailored GRIN Luneburg lens antenna in which five commercial FMCW radar modules simultaneously excite a single shared aperture. Although a conventional Luneburg lens effectively focuses individual feeds, its purely radial phase profile is not optimized to control the composite electromagnetic response of multiple simultaneously excited off-axis commercial radar feeds. The proposed TLL introduces fabrication-aware non-radial volumetric phase control to reorganize this composite response into predefined sensing sectors while also improving adjacent-channel isolation near the design frequency. A 10-cm-diameter lens is designed and fabricated for five 58–63 GHz radar modules targeting sectors centered at −56°, −28°, 0°, +28°, and +56°, corresponding to approximately 140° of sectorized angular coverage. Under simultaneous five-port excitation, full-wave simulations show that the CLL composite response exhibits substantial central crowding and displaced sector maxima, whereas the TLL forms five dominant lobes near the prescribed directions with peak realized gains of approximately 20–22 dB. The TLL also produces frequency-selective adjacent-channel coupling minima of approximately −50 to −70 dB near 60 GHz. Experimental validation demonstrates approximately 10–13 dB received-power enhancement across the operating band together with threshold-based sector-selective target detection. These results demonstrate a passive shared-aperture approach for simultaneous multi-beam millimeter-wave radar sensing using commercial radar-module feeds.
