Isolation Improvement of Two Tightly Coupled Antennas Operating in Adjacent Frequency Bands Using Filtering Structures

Abstract

In this paper, a mutual coupling reduction technique using filtering structures between two antennas resonating in adjacent frequency bands is proposed. Two patch antennas resonating at low band (4.8-5.0 GHz, part of 5G Band N79) and high band (5.15-5.35 GHz, part of IEEE 802.11 ax 5 GHz Band), which are close to each other in frequency spectrum, are used as an illustrative example. The decoupling structure consists of two open-loop resonators with filtering function coupled to the feed line on its edges. By loading the filtering structures, the isolation between the two antennas is improved from poorer than 15 dB to more than 25 dB when the reflection coefficients are still satisfactory in their respective operating frequency bands, showing significant improvements compared to the reference antennas where no filtering structures are introduced. The proposed method can be easily applied to either mobile terminal or 5G CPE (Customer Premise Equipment) devices where both 5G and Wi-Fi are installed as well as many other antennas with similar application scenarios.