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. INDEX TERMS Adjacent frequency bands, filtering structures, mutual coupling reduction, patch antenna, Wi-Fi, 5G.

Mutual Coupling Suppression Between Two Closely Placed Patch Antennas Using Higher-Order Modes

“…Additionally, the proposed method is unique in its capacity to address both in-band and adjacent-band decoupling issues and can be applied to multi-element MIMO arrays. In contrast, other works either require the utilization of additional decoupling layers [7], [14] or demand a more involved design of decoupling structures [12], [23]. The proposed method, on the other hand, is comparatively simpler and does not necessitate the use of additional layers or interantenna decoupling elements, thereby making it a costeffective and efficient design solution.…”

“…Another problem with these decoupling methods is that most of them are very sensitive to the symmetry of the antennas to be decoupled and are only verified effective for two identical antennas. However, the decoupling problem between two different antennas is also very important [22][23][24]. For a commercial device supporting different standards for different regions, multiple antennas operating over different frequency bands must be well-isolated.…”

Scattering Suppression of Closely-Packed Cross-Band Patch Antennas Using Absorptive/Reflectionless Filtering Techniques

“…The last scattering-suppression method incorporates the filtering functionality into the antenna, leading to the so-called "filtering antennas" [18]- [20]. Note that, as shown in Fig.…”