Ultra-thin metasurface microwave flat lens for broadband applications

TLDR

The study presents an ultrathin metasurface flat lens for microwave frequencies. The lens is realized with a tri‑layer stack of split‑ring resonators and cross‑polarized gratings that generate a radially symmetric parabolic phase profile spanning 0 to 2.5π. Measurements show broadband focusing from 7 to 10 GHz with a 17 dBi gain at 9 GHz, a focal length matching design, a 3 dB beamwidth below 4.5°, and high‑quality collimation, demonstrating a lightweight, low‑cost flat transceiver.

Abstract

We demonstrate a metasurface-based ultrathin flat lens operating at microwave frequencies. A series of subwavelength metallic split-ring resonators, which are sandwiched between two cross-polarized metallic gratings, are defined to obtain a radially symmetric parabolic phase distribution, covering relative phase differences ranging from 0 to 2.5π radians to create a lens. The tri-layer lens exhibits focusing/collimating of broadband microwaves from 7.0 to 10.0 GHz, with a gain enhancement of 17 dBi at a central wavelength 9.0 GHz while fed by a rectangular horn antenna. The measured focal length agrees reasonably well with design, achieving a 3 dB directionality <4.5° and confirming high-quality beam collimation along the propagation direction. The demonstrated metasurface flat lens enables light-weight, low-cost, and easily deployable flat transceivers for microwave communication, detection, and imaging applications.