A novel wideband decoupling technique for MIMO antenna arrays is proposed. Broadband isolation is achieved by creating controllable transmission zeros (S21=0) at two separated frequencies. The newly developed decoupling network is compact in size due to the elimination of multiple transmission line elements and the external matching circuit. Simulation and measurement results show that the proposed method can offer substantial enhancement in port isolation, pattern diversity (ECC) and radiation efficiency over the designated frequency range.

A novel dual-band decoupling and matching technique for asymmetric two-element antenna arrays is proposed. Decoupling and matching at two widely separated frequencies is accomplished by using a two-layer (level) network approach. Unlike previous works, analytical solution is readily available and prematching of the radiating elements is no longer required. Simulation and experimental results show that the proposed method can offer improved port isolation and input return loss, enhanced efficiency, and increased radiation pattern diversity in both frequency bands.

This article presents a novel and simple method for the decoupling of a $2\times 2$ MIMO antenna array. Two distinct radiation modes, with different patterns and polarizations, are created by a novel patch element design. This new configuration enables the excitation of additional coupling paths between antennas, and ultimately the neutralization of mutual coupling. Since the two radiating modes are generated by the same patch element, the proposed MIMO antenna also features simple structure and compact size. For verification, a $2\times 2$ MIMO antenna with center-to-center spacing of $0.475\lambda _{0}$ is prototyped and characterized. Simulation and experimental results reveal that the proposed design can offer enhanced port isolation, antenna efficiency, and pattern diversity.

In this paper, a multi-element fully-decoupled linearly-placed inverted-F antenna (IFA) array is proposed for mobile terminals. A hybrid decoupling method is used to mitigate the mixed types of mutual couplings among the multiple IFAs: introducing multiple decoupling capacitors for the couplings of two back-to-back IFA pairs and T-shaped mode transformers for the remaining couplings. The decoupling capacitors not only decouple the back-to-back IFA pairs but also broaden the impedance bandwidth of each IFA. The T-shaped mode transformer transforms the concerned antenna from an IFA mode into a balanced loop mode, preventing the induced current on the victim IFAs of the face-to-face and back-to-face pairs. One four-element example and one eight-element example are designed and measured to justify the proposed decoupling concept. The measured results of the four-element IFAs show that after decoupling, all the six mutual couplings among the four IFAs are reduced by about 10 dB from 3.3 to 3.8 GHz, with average total efficiencies throughout the band improving from 57 % to 72 % for IFA 1 and from 47 % to 55 % for IFA 2. An eight-element IFA array is built utilizing the pattern diversity of two proposed four-element IFA blocks, achieving inter-block isolation of better than 20 dB. And a six-element linear IFA array is also designed to prove the generality of the proposed method.

A novel decoupling method for printed-dipole antenna arrays based on the shaping of the antenna elements is presented. By the proper meandering of the radiating elements, different coupling modes are generated and combined for the enhancement of port isolation. In addition, optimal conditions for ideal cancellation of mutual coupling are thoroughly investigated. Compared with traditional decoupling approaches, the proposed method features design flexibility (elimination of any external decoupling structure) and improved port isolation, radiation efficiency, and pattern diversity (ECC). For verification, both simulation and experimental studies of various printed-dipole antenna arrays operating at 2.45 GHz are given.

A self-decoupled wideband slot MIMO antenna pair is proposed in this letter. The two slot antennas are bent into two perpendicular portions, and the current directions on one portion of the two antennas are the same and those on the other ones are opposite to make the total current coupling cancel out with each other, so the first transmission zero is achieved. To widen the decoupling bandwidth, another short-ended slot is introduced around the center point of the original slot antenna to maintain the first transmission zero. Based on the same current coupling cancellation mechanism, a second transmission zero can be generated at this higher frequency, so a wideband self-decoupled MIMO antenna design is achieved. One two-element demonstrational example working in the N78 band (3.3 – 3.8GHz) is simulated and measured. The results show that the proposed slot antennas achieve isolation of better than 20 dB and matching conditions of better than -10 dB within the N78 band. Besides, the envelope correlation coefficient (ECC) is less than 0.006, and the average total efficiency is about 80%. Another four-element linear array is also designed and measured to justify the generality of the proposed method.