A High-Isolation Building Block Using Stable Current Nulls for 5G Smartphone Applications

Abstract

In this paper, a new design method to enhance the isolation of a two-antenna building block is introduced. Here, a two-antenna building block (Ant 1 and Ant 2) that is composed of a gap-coupled loop antenna (Ant 1) and a loop antenna (Ant 2) is meticulously designed to allow Ant 1 to excite a standingwave region that can be formed on the structure of Ant 2. To exhibit high isolation (26 dB) between the two antennas, the stable current null point existed in the standing wave region is exploited and designed to fall at the feed point of Ant 2 during the excitation of Ant 1. By employing this proposed building block, a fourport multiple-input multiple-output (MIMO) system and an eight-port MIMO system operating in the long term evolution (LTE) band 42 (3.4-3.6 GHz) are implemented. The proposed four-antenna and eight-antenna MIMO arrays can yield desirable measured isolation of better than 23 dB and 17.9 dB, respectively, over the band of interest, and their respective measured ECCs (envelope correlation coefficients) were lower than 0.032 and 0.075. To further evaluate the MIMO performances of the presented MIMO arrays, their ergodic channel capacities are also investigated.INDEX TERMS Fifth-generation (5G) smartphone, multiple-input multiple-output (MIMO), building block, high isolation.

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

“…As shown in Table 1, the selfdecoupling technique has superiority in compactness and simple implementation when compared to the aforementioned decoupling techniques, such as decoupling network, additional resonators, and spatial arraignment. The proposed self-decoupled MIMO set exhibits comparable isolation and bandwidth performance but has a simpler implementation compared to [18] and [22].…”

“…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.…”

Design of MIMO antenna system operating in wideband of 3300 to 6400 MHz for future 5G mobile terminal applications

“…It is interesting to note that there are several literatures have begun to focus on how to realize higher isolations in the MIMO antenna systems in the last year or two, and many good solutions have been proposed therein. [34][35][36][37][38][39][40][41][42][43][44] In which, for example, the decoupling techniques of self-isolated antenna element, self-decoupled MIMO antenna pairs, orthogonal polarization, pattern diversity, multimode decoupling, the tiny neutralizing line, and metasurface-based decoupling have been respectively reported. Although these methods can effectively achieve higher or at least improved isolations between antenna elements when 10 dB is used as the minimum requirement for isolation, they only considered the cases of single-or dual-band MIMO operation.…”