Closely-Spaced, Wideband, High-Isolation Microstrip Antennas Using Multiple-Decoupling Method

A multiple-decoupling method is proposed for closely-spaced, wideband, and high-isolation microstrip antennas. In this approach, multiple-decoupling structures are introduced to gradually improve the port isolation between two wideband antennas. Specifically, the capacitively loaded pins are uniformly distributed across two diagonal lines of the shared patch radiator, forming a capacitively loaded fence (first-stage decoupling structure). To further enhance port isolation, a pair of quarter-wavelength open-ended slots are etched on the non-radiating edge of the microstrip antenna to constitute the second-stage decoupler. With only sacrificing 3% of impedance bandwidth, the maximum isolation is increased from 18 dB to 53 dB. After fabrication and measurement, the proposed antenna almost covers Wi-Fi 6 (5.15-5.83 GHz) and Wi-Fi 6E (5.92-7.125 GHz) with an impedance bandwidth of 5.39-7.57 GHz (33.6%) and in-band isolation better than 23.3 dB. With the merits of close spacing, wideband, and high isolation, the proposed antenna pair possesses the potential for Wi-Fi 6 and Wi-Fi 6E applications.