Millimeter-Wave Thin Lens Employing Mixed-Order Elliptic Filter Arrays

This communication presents a novel approach for designing a simplified and cost-effective millimeter-wave thin lens by reducing the number of substrates and metal layers for a given tunable range of the phase shift. It is demonstrated that this can be achieved by employing mixed-order elliptic filter arrays where the different orders of the filter are responsible for different tunable ranges of the phase shift. The key features of the elliptic filters and their mixed-order array are introduced. It is found that constructively utilizing the interlayer coupling between the metal layers renders an elliptic filter response, and the mixed-order configuration of the elliptic filter array can be utilized to design the devised thin lens. The design procedure for the affordable thin lens configuration is discussed. The empirical and simulated results demonstrate that the conventional planar lens can be further simplified in terms of the number of substrates and metal layers, maintaining the tunable range of the phase shift. It is confirmed that the fabricated mixed-order lens is less than 0.05 λ0 in total thickness and has a gain of up to 12 dB with f/D = 0.7.