Ultra-wideband, true-time-delay, metamaterial-based microwave lenses

In this paper, a new technique for designing low-profile, ultra-wideband, true-time-delay (TTD) microwave lenses is proposed. Such a lens is composed of numerous spatial TTD units distributed over a planar surface. Each spatial TTD unit is the unit cell of an appropriately-designed metamaterial structure, which is composed entirely of non-resonant constituting elements. The proposed TTD lens is a low-profile structure with an overall thickness of only 0.15λ₀ and uses spatial TTD units with dimensions of 0.19λ₀ × 0:19λ₀, where λ₀ is the free-space wavelength at the center frequency of operation. Unlike most metamaterial lenses, which tend to be narrow band and highly dispersive, the proposed lens has a wide operational bandwidth of 30% and a high system fidelity factor close to 1. Furthermore, due to its true-time-delay nature, the fabricated lens prototype does not suffer from chromatic aberration within its operational band. When used in a beam-scanning antenna system, the fabricated prototype demonstrates an excellent scanning performance in a field of view of ±60°.