A wideband isolation technique using bezel coupled T-type isolator for smartwatch MIMO applications

This letter presents a wideband bezel coupled T-type isolator, decoupling two antenna elements for smartwatch multiple-input multiple-out applications. The antenna elements consist of PIFA antennas operating at 2.45 GHz, covering Bluetooth and Wi-Fi bands. The proposed T-type isolator has been installed between the antenna elements made by inserting two slits in the bezel separated by 21 mm. The separated segment of the bezel is connected with the circular ground plane by a conducting strip and an inductor. In this way, the slits offer stray capacitance, and the capacitive coupling between the T-type isolator has been utilized to achieve a wide isolation bandwidth. Meanwhile, the isolation can also be tuned using the gaps of the slits and the inductor. The design performance has been validated in simulations and measurement. The measured impedance bandwidth is higher than 120 MHz whereas the isolation bandwidth is 790 MHz with a maximum isolation higher than 22 dB. The measured envelop correlation coefficient is below 0.01. The proposed design is a good candidate for smartwatch applications.