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 LLs (sLLs) into flat lenses via transformation optics. 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 at 5 GHz). Experimental results indicate that the prototype achieves a gain range of 17.68 dBi to 18.54 dBi over a frequency band of 4.7 GHz to 5.2 GHz, which shows good coincidence with simulated ones.