# Eight-Port Modified E-Slot MIMO Antenna Array with Enhanced Isolation for 5G Mobile Phone
## 1 Introduction  
In a communication system, the use of the multiple-input multiple-output (MIMO) antenna technique significantly enhances the channel capacity, spectral efficiency, and reliability link without the additional requirement of increased bandwidth and power [1; 2; 3]. As compared to the existing infrastructure of 4G devices which uses at most four radiating elements, the 5G system utilizes a minimum of six to eight elements for efficient transmission [4; 5; 6; 7]. The increased demand for faster data rates with exceptionally low latency is outpacing the present LTE advanced technology [8; 9; 10; 11; 12]. This results in the adoption of the 5G communication systems, which can deliver data throughput with a much lower latency of \(<\)1 ms in comparison to 4G-LTE [13] and intra-band contiguous carrier aggregation to increase the data throughput. Arranging multiple antennas in a size-limited environment is challenging since the radiation among antenna elements disturbs the radiating environment of the neighboring antennas, thus reducing the overall performance of the system. To achieve promising outcomes of such a design, the level of isolation among the elements needs to be greater than 12 dB [14]. Several techniques do exist in most of the recent literature to alleviate the effect of coupling among closely packed antenna elements [15; 16]. These isolating structures include neutralization lines [17; 18], decoupling networks [19; 20], electromagnetic band gap [21], parasitic elements [22], orthogonal modes [23], pattern diversity arrangement [24], and multi-mode decoupling schemes [25].  
Various MIMO antennas have been proposed in recent years [14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. The work in [7] presented an eight-element antenna covering 3.4-3.6 GHz on a side frame which gained isolation of more than 17.5 dB, efficiency greater than 62%, and ECC lower than 0.05 using a slot radiator, but this design required a lot of space for the antenna element. Similarly, in [27] a tri-polarized 12-element MIMO antenna using an orthogonal polarization technique was investigated. The author employed two open-ended slot antennae that operated in the 3.5 GHz (3.4-3.6 GHz) bands and attained elements isolation of 12.5 dB, an efficiency of more than 50%, and an ECC of less than 0.2 are obtained. The work in [18] employed a hybrid method to mitigate the mutual coupling among the antenna elements by introducing an I-slot and a neutralization line. They achieved an isolation value of more than 15 dB in the 3.3-3.6 GHz. An eight-antenna array in [28], was proposed for operation in the 3.5 GHz band with no external decoupling element. Yet, they achieved the isolation of 10 dB and a channel capacity of 36 bps/Hz. However, the methods in [27; 28] suffered from complexity and lower isolation level. An eight-antenna array covering the LTE band 42 with less complexity is presented in this article for 5G smartphone applications. Our proposed design includes an E-shaped slot element on the ground to effectively provide isolation between neighboring antenna elements by lowering the grounded current effects. The designed antenna array achieved higher isolation (>21 dB), better maximum efficiency (>76%), lower ECC (<0.01), and channel capacity of up to 43.50 bps/Hz over the range of interest between any two radiating elements.  
This work presents an eight-element MIMO antenna system with high isolation using E shape DGS scheme. The proposed design after the inclusion of the proposed DGS offers good isolation of >21 dB within the desired band with high-performance characteristics. This article is organized as follows. Section 2 describes the antenna configuration with array transformation. Section 3 presents the parametric sweep, experimental results, and discussion with MIMO performance evaluation matrices. Finally, Section 4 is the conclusion of this paper.