Metasurface-augmented gradient-index lenses for millimetre-wave applications

Abstract

This research project aims to develop metasurface-augmented gradient index (GRIN) lenses for millimetre-wave (mmWave) applications. It introduces a concept combining GRIN lenses with metasurfaces, enhancing the ability to direct beams of high-gain GRIN lens antennas and control focal positions in GRIN lens beamformers. A novel methodology for designing the metasurface is established by analysing the electric field phases within a GRIN lens along with the phase shift in a single unit cell, using full-wave simulation tools available to researchers.

The research investigates two GRIN lenses: the 2D Luneburg lens antenna and the 2D Maxwell fisheye lens (MFL) beamformer in reflective and transmit modes. By integrating a half-circle Luneburg lens antenna with a variable-sized square patch reflectarray, beamsteering with a maximum angle of 75° was achieved across a frequency range of 26 – 28 GHz. The operational bandwidth extended to 24 – 38 GHz with a wideband Phoenix reflectarray. The half-circle Maxwell fisheye lens (HMFL) beamformer maintained its focal axis and achieved a maximum angle of 45° within a frequency range of 26 – 28 GHz. This was extended to 22 – 32 GHz using the Phoenix reflectarray. Both lenses were evaluated at normal incidence (0°) and oblique incidences (-15° and -30°).

In transmit mode, the GRIN lenses were modified with an all-dielectric phase correction layer composed of cubic unit cells. This layer, placed vertically between two half-circle lenses, formed a 2D circular transmitarray-augmented Luneburg lens antenna, generating directive beams with a maximum angle of 75° across 24 – 30 GHz. The MFL beamformer, combined with the phase correction layer, focused incident energy, achieving a maximum angle of 45° across 22 – 32 GHz.

This research explores 3D printing techniques for fabricating GRIN lenses and transmitting metasurfaces and printed circuit board (PCB) technology for the reflective metasurfaces, enabling cost-effective laboratory prototype production.

Thesis is embargoed until 31st December 2025.

Date of Award	Dec 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Jouf University
Supervisor	Dmitry Zelenchuk (Supervisor) & Muhammad Ali Babar Abbasi (Supervisor)