A Novel Versatile Decoupling Structure and Expedited Inverse-Model-Based Re-Design Procedure for Compact Single-and Dual-Band MIMO Antennas

Abstract

Multiple-input multiple-output (MIMO) antennas are considered to be the key components of fifth generation (5G) mobile communications. One of the challenges pertinent to the design of highly integrated MIMO structures is to minimize the mutual coupling among the antenna elements. The latter arises from two sources, the coupling in the free space and the coupling currents propagating on a ground plane. In this paper, an array of H-shaped parasitic patches is proposed as a decoupling structure for compact MIMO antennas to reduce propagation of the coupling currents on a shared ground plane. The proposed decoupling structure is generic, and it can be applied to different antenna configurations as demonstrated in the work. Furthermore, it is employed to develop a new high-performance compact dualband MIMO structure featuring acceptable level of element coupling at both operating frequencies. The design is validated both numerically and experimentally. The mutual coupling levels are less than -17 dB and -20 dB, with the total efficiency of 89% and 90%, and the realized gain of 6.6 dB and 7 dB at the two resonant frequencies of 5 GHz and 6 GHz, respectively. Topological complexity of the compact MIMO systems featuring elaborated decoupling structures, a large number of geometry parameters, as well as the necessity of handling multiple performance figures, constitute the major challenges of antenna design, in particular, its re-design for various specifications. To alleviate these difficulties, the paper also provides a procedure for rapid geometry scaling of the dual-band MIMO antennas. Our approach is based on inverse surrogate modeling methods, and results in numerically-derived expressions that enable a precise control over the operating antenna bands within broad ranges thereof (from 4 GHz to 8 GHz for the lower band, and from 1.1 to 1.3 ratio of the upper to lower operating frequency). The aforementioned procedure is accompanied by an optimization-based design refinement scheme. A practical utility of the procedure is corroborated using multiple verification case studies as well as physical measurements of the antenna designed for the exemplary set of performance specifications.INDEX TERMS Multiple-input multiple-output (MIMO) antennas, decoupling, inverse modeling, isolation, expedited redesign.

A Multi-Frequency Low-Coupling MIMO Antenna Based on Metasurface

“…In [23,24], SRRs were loaded on the antenna plane for decoupling surface waves and certain space waves. In [25][26][27][28][29], the effective decoupling of antennas was achieved by loading them with metasurfaces. The decoupling method using metamaterials has a smaller impact on antenna size and radiation performance in resonance bands, and it provides good decoupling effects.…”

A Compact Dual-Band MIMO Antenna for Sub-6 GHz 5G Terminals

“…Additionally, defected ground structures (DGS) can improve isolation by affecting the circuit substrate's effective dielectric constant distribution-this has become a commonly used technology for overcoming undesired coupling in MIMO antenna designs [11][12][13][14]. Some MIMO antennas use unique decoupling structures to improve isolation, such as the multi-slot decoupling structure [15], the generic decoupling structure composed of an array of H-shaped parasitic structures [16], and the rectangular microstrip stub [17].…”

Two-stage variable-fidelity modeling of antennas with domain confinement

“…The main concept is to construct the surrogate in a small portion of the parameter space, which encloses the designs being nearly optimum with regard to the target objective vectors. The computational benefits are due to a small volume of such a subset and a smaller sizes of training data sets that are needed to construct model of a satisfactory predictive power 75 .…”