A Luneburg Lens-Inspired Flat Lens Antenna With High Gain via Reduced Reflection Loss

A discretized Luneburg lens-inspired (LL-inspired) flat lens antenna is proposed for high-gain applications. Traditional LL-inspired flat lens antennas usually suffer from the reflection loss that occurs during the transformation of spherical Luneburg lenses (sLLs) into flat lenses via transformation optics (TO). Based on cascaded transmission-line models, a concise discretizing formula is applied to adjust the dielectric distribution of the lens, enabling it to achieve wave impedance quasi-matching for reduced reflection loss. Utilizing this method, the proposed LL-inspired flat lens antenna realizes a gain enhancement of 0.8 dB at 5 GHz compared to reference cases, comparable to the ideal sLL antenna. Finally, a prototype of the proposed antenna was fabricated by 10-layered drilled substrates. The overall dimension of the prototype antenna is 2.67λ0×2.67λ0×1.67λ0 (λ0 @ 5GHz). Experimental results indicate that the prototype achieves a gain range of 17.68-18.54 dBi over a frequency band of 4.7-5.2 GHz, which shows good coincidence with simulated ones.