True-Time-Delay Metasurface Assisted Broadband and Planarized Resonant Cavity Antenna

Resonant cavity antennas (RCAs) produce reasonably high gains (15-20 dBi) with thin form factors, and find strong applications in wireless communication. A recently proposed RCA achieves a broad 3dB bandwidth of over
${20\%}$
using a spherically modified ground (SMG), but its curved metallic surface is very costly to manufacture at high frequencies. In this paper, we planarize this broadband RCA by replacing the SMG with a true-time-delay metasurface (TTD-MS) which mimics the both reflection phase shift and time-delay of the SMG over antenna’s entire operation bandwidth. We verify our proposed method through full-wave simulations and experimental measurements. Our measurements demonstrate an impedance bandwidth
$({\rm S_{11}\le -10\:{\mathrm{ dB}}})$
of
${32\%}$
and a 3dB-gain bandwidth of
${21.3\%}$
(from 11.95 GHz to 14.8 GHz), with a peak gain of 17.5 dBi. This performance is comparable to the RCA with the SMG, but we have planarized the structure, leading to dramatic simplification in fabrication. The height of the cavity is also reduced by
${20\%}$
. The proposed TTD-MS RCA exhibits high gain, stable impedance matching, reduced cavity height and simple configuration, and elucidates a new path to RCA design for microwave and mm-wave frequencies.