Ultralow-Profile and Ultrawideband Microstrip Patch Antennas Based on Hybrid Coupling for Mobile Wi-Fi 6/6E and UWB Channels 5–11 Applications

Achieving ultrawideband antennas under the ultralow profile continues to be a significant challenge, particularly for mobile devices with limited space. This communication proposes an innovative wideband antenna for Wi-Fi 6/6E (5.15–7.125 GHz) and UWB channels 5–11 (5.949–8.653 GHz) applications. The antenna features a half-mode patch as the primary radiating patch functioning at both fundamental and second-order modes. To broaden the bandwidth, a hybrid coupling method of two parasitic patches is strategically incorporated: one is on the open-ended side in a “mouth-to-mouth” configuration excited via electric coupling and another is on the shorting-via side in a “back-to-back” configuration excited by magnetic coupling. The hybrid coupling makes the single resonance into three distinct resonances, greatly enhancing impedance and efficiency bandwidths. Finally, the proposed antenna achieves five resonant frequencies covering the target bands (5.15–9 GHz). A 4 x 4 multiple-input-multiple-output (MIMO) prototype with compact dimensions (54.1 x 54.1 x 1 mm³) demonstrates a measured −6-dB impedance bandwidth of 5.05–9.0 GHz, interelement isolation >14.4 dB, and total efficiency ranges from 53% to 77.6%. To the best of the authors’ knowledge, the proposed antenna attains the largest bandwidth-to-profile ratio (BPR) of 33.1 compared to other reported planar antennas with the ultralow profile of 1.0 mm, showcasing the great potential to be applied in mobile terminals.