A Sub-Terahertz Wideband Stacked-Patch Antenna on a Flexible Printed Circuit for 6G Applications

In this article, a wideband aperture-coupled stacked-patch (ACSP) antenna on a flexible material for wireless applications at the WR-08 band is presented. It is shown that conventional designs of ACSP fail to achieve a large bandwidth at this frequency range, and a novel design methodology is proposed. We first propose a broadband impedance matching between the input port and the slot aperture based on two-section wideband distributed network (TWBDN). We also propose a TWBDN matched stacked patch (TMSP) network based on constant VSWR circles to attain broadband matching between the slot aperture and patches in an ACSP. To facilitate the measurements, a novel low-loss transition from a ground-signal-ground (GSG) port to a feedline is proposed. The proposed structure suppresses surface waves induced in the WR-08 band by placing via arrays around the feedline, which largely reduces unwanted resonance modes, thereby leading to uniformly high radiation efficiency across the band. The measured results of the fabricated antenna closely follow the simulations, and a measured peak gain of 7.95 dBi and $S_{11}\leq -10$ dB across a wide frequency range from 90 to 128.5 GHz is achieved.