Eight-Port MIMO Array Using Characteristic Mode Theory for 5G Smartphone Applications

Abstract

An 8-port multiple-input multiple-output (MIMO) array operating in the long-term evolution (LTE) band 42 (3400-3600 MHz) based on the characteristic mode theory (CMT) is described. As designing a multi-antenna system with multiple significant modes is difficult for the CMT, a new method is, therefore, proposed to effectively provide useful physical insights and improve the envelope correlation coefficient (ECC). Although many of the same modes are excited by two antennas, the proposed method is still effective to improve the ECC of the two antennas. A detailed and reasonable framework adopting the CMT to analyze geometries with multi-significant modes is presented. The consideration of the mode number can be avoided by using this method. For an arbitrary structure, it is verified that the modal weighting coefficient (MWC) phases of the same modes excited by two ports are in phase or out of phase. Therefore, for the design of a multi-port MIMO array, the same modes excited by different ports can be divided into two types: equiphase modes and antiphase modes in the proposed method, and the tradeoff of the equiphase modes and the antiphase modes is first proposed and analyzed as an efficient way to improve the ECC. Furthermore, the proposed method can also be applied to asymmetric structures. In order to prove the effectiveness of the proposed method in the design of MIMO antennas with desirable ECC, an 8-port MIMO array for 5G mobile applications is implemented and measured.INDEX TERMS Multiple-input multiple-output (MIMO), characteristic modes, 5G mobile application.

A Compact and Straightforward Self-Decoupled MIMO Antenna System for 5G Applications

“…With the allocation of the 3.5 GHz (3.4-3.6 GHz) band for 5G wireless communication [5], the sub-6 GHz MIMO antenna systems have been popularly studied to allow more antenna elements to be integrated into space-scarce terminal devices [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. It has been demonstrated that high isolation (i.e., low mutual coupling) and low correlation are essential figure-of-merits for MIMO antenna systems to guarantee excellent radiation performance and diversity property.…”

“…In the literature, the previously reported techniques for the sub-6 GHz 5G MIMO antennas can be categorized into the following two categories: decoupled MIMO antenna arrays by utilizing decoupling structures [6][7][8][9][10][11][12] and selfdecoupled MIMO antenna arrays without any additional structures [13][14][15][16][17][18][19][20][21][22][23]. For the decoupled MIMO antenna arrays, the frequently adopted decoupling structures include neutralization lines or decoupling networks [6][7][8][9], and additional resonators [9][10][11][12], which require additional occupation and complicated tuning efforts.…”

“…For the decoupled MIMO antenna arrays, the frequently adopted decoupling structures include neutralization lines or decoupling networks [6][7][8][9], and additional resonators [9][10][11][12], which require additional occupation and complicated tuning efforts. On the contrary, the self-decoupled MIMO antenna arrays can achieve adequate isolation by proper arrangement [13][14][15][16][17] and polarization or pattern control [18][19][20][21][22][23], circumventing the case-by-case implementation of extra decoupling structures. However, some of them require vast distances between each two antenna elements [13][14][15][16][17], which severely limit the scale of the integrated antennas; in contrast, others suffer from structural complexity, implementation difficulty, or constrained position requirements.…”

“…On the contrary, the self-decoupled MIMO antenna arrays can achieve adequate isolation by proper arrangement [13][14][15][16][17] and polarization or pattern control [18][19][20][21][22][23], circumventing the case-by-case implementation of extra decoupling structures. However, some of them require vast distances between each two antenna elements [13][14][15][16][17], which severely limit the scale of the integrated antennas; in contrast, others suffer from structural complexity, implementation difficulty, or constrained position requirements. Therefore, compact and straightforward self-decoupled MIMO antennas with simple structures and cost-effective implementation is favorable in practical applications.…”

Miniaturized-Element Frequency-Selective Rasorber Design Using Characteristic Modes Analysis

“…The characteristic mode analysis has attracted considerable attention in design and optimization of antennas [19]- [20], because it provides not only a clear physical insight into radiation behavior but also information of significant radiation modes that can be excited. It also has been applied for design and analysis of multiport networks such as antenna arrays [21], the metasurface resonator antennas [22], platform mounted antennas [23] and also aircraft-integrated multiband multiantenna systems [24]. However, to our best knowledge, few publications were presented on the frequency-selective surface design using the CM theory.…”