Distributed Impedance Synergy Antenna: A Novel Strategy to Realize Low-Profile and Wideband Patch Antenna for Mobile Terminals

Designing back-cover planar mobile antennas with profiles of less than 0.5 mm at Sub-6 GHz is a significant challenge, as traditional wideband low-profile techniques like slotted, stacked, and multimode patches are constrained for such scenarios. This letter proposes a novel strategy called distributed impedance synergy to address this issue. By identifying two identical impedance points on a single antenna and feeding them with a 90° phase difference, the reflections coming from these two points can be cancelled and wideband matching can be achieved. Commercial balun chips are used to provide the required phase difference. The proposed strategy is applied to two back-to-back half-mode patch pairs: under the profile of only 0.35 mm (0.006λ0), the first pair operating at TM0.5,0 mode exhibits a measured -10 dB impedance bandwidth of 210 MHz [(5.43 to 5.64) GHz] and the second operating at TM0.5,0 and TM0.5,1 modes exhibits a bandwidth of 450 MHz [(5.23 to 5.68) GHz] covering Wi-Fi band. To the best of the authors' knowledge, these are the first planar antennas to achieve wideband coverage with a profile of only a few thousandths of an electrical wavelength and they achieve the highest space usage rate compared to existing low-profile antennas.