Ultrathin Flexible Dual-Band Dual-Polarized Antenna for mmWave 5G Wearable Electronics

Abstract

An ultrathin, dual-band, dual-polarized antenna with improved isolation between the two polarizations, designed on a 248- $\mu $ m thick flexible printed circuit (FPC) board, is presented in this article. In thin flexible millimeter-wave (mmWave) antennas, maintaining high isolation between orthogonal polarizations across two-frequency bands is particularly challenging due to strong coupling through the patch structure and limited substrate thickness. To address this issue, an asymmetric dual-polarized patch antenna employing a partial differential feeding technique is proposed, in which only one port is differentially fed using a wideband coupled-line phase shifter integrated with a T-junction. This configuration effectively suppresses coupling and enhances isolation. The proposed antenna operates simultaneously in the 27.5–28.7-GHz and 37–38.5-GHz bands, achieving measured isolation better than −25 dB between the two polarizations.