A gain-reconfigurable flat gradient refractive index plasma lens

This paper presents a novel reconfigurable flat gradient-index (GRIN) lens antenna utilizing plasma dielectric materials. The lens structure consists of multiple nested cylindrical plasma layers whose plasma frequencies are controllable by adjusting the excitation parameters in each plasma layer. It is demonstrated that the control over the plasma permittivity of different layers enables agile beam shaping of the lens antenna. Analytical equations for the design of GRIN plasma lenses with optimal dimensions and radiation gain are derived. Numerical simulations based on the analytical design equations demonstrate a gain enhancement of over 10 dB for the antenna using GRIN plasma lens. For the experimental proof-of-concept, a one-dimensional low-cost prototype of the proposed GRIN plasma lens is realized using commercial fluorescent lamps. Experimental results confirm gain enhancement of the utilized feeding horn antenna at the E-plane, reaching approximately 3.5 dB when the plasma lens is excited. The close agreement between simulated and measured results validates the proposed concept, analytical model, and design methodology. To benchmark the proposed system against recent advances, a comparative analysis is included, highlighting the distinctive features of the flat GRIN plasma lens in terms of its reconfigurability, beam control capabilities, and practical implementation aspects.