Passive Time Delay Metasurfaces for Resonant Cavity Antennas

Abstract

This thesis presents several wideband Resonant Cavity antenna (RCA) designs employing passive time delay metasurfaces (PTDMs). The RCAs have been the focus of rigorous study in recent years due to their ability to provide high gain with compact, low profiles and fabrication simplicity compared to bulky horns or corporate-fed arrays. However, the narrow operational bandwidth is a significant challenge associated with the design of RCAs. In this thesis, we show that integrating planar PTDMs inside and outside the cavity of RCAs can yield several benefits, such as compact sizes and wide bandwidths. The proposed PTDMs are artificially engineered structures with subwavelength thicknesses, designed with special unit cells providing linearly varying phase responses with respect to frequency—and therefore constant delays. We provide a general synthesis procedure to design such PTDM structures. We demonstrate the key functionalities of PTDMs for the RCA in the following ways: (1) excitation of the high-order cavity modes inside the RCA cavity when implemented as the ground plane; 2) attaining wider 3dB gain bandwidths when implemented as a phase-correcting metasurface in the near field of the RCA. 3) overcoming the issues of sidelobes for higher-order cavity modes when implemented as a phase-correcting metasurface in the near field of the RCA.

Date of Award	16 Sept 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Man Hon Alex WONG (Supervisor)