Abstract
In this paper, the systematic design of a multiple antenna system for 5G smartphone operating at 3.5 GHz for multiple-input multiple-output (MIMO) operation in smartphones is proposed. The smartphone is preferred to be lightweight, thin, and attractive, and as a result metal casings have become popular. Using conventional antennas, such as a patch antenna, Inverted-F antennas, or monopole, in proximity to metal casing leads to decreasing its total efficiency and bandwidth. Therefore, a slot antenna embedded in the metal casing can be helpful, with good performance regarding bandwidth and total efficiency. The proposed multiple antenna system adopted the unit open-end slot antenna fed by Inverted-L microstrip with tuning stub. The measured S-parameters results agree fairly with the numerical results. It attains 200 MHz bandwidth at 3.5 GHz with ports isolation of (≤−13 dB) for any two antennas of the system. The influence of the customer’s hand for the proposed multiple antenna system is also considered, and the MIMO channel capacity is computed. The maximum achievable MIMO channel capacity based on the measured result is 31.25 bps/Hz and is about 2.7 times of 2 × 2 MIMO operation.
Highlights
With evolving semiconductor technology, the electronic communication components can be packed closely to design compact structures with high processing capabilities, such as a smartphones and wireless routers [1]
The design of the proposed multiple antenna system evolved from an open-end rectangular shape slot etched at the top edge, called the reference antenna or Ref_Ant, and fed by the inverted-L microstrip printed on the opposite side of the substrate
As evident with the length of 8 mm, the unit slot or the Ref_Ant1 failed to operate for the desired band of 3.5 GHz for Figure 3a.The slot antenna is usually treated as a magnetic dipole, with its first resonating frequency depending on its electric length
Summary
The electronic communication components can be packed closely to design compact structures with high processing capabilities, such as a smartphones and wireless routers [1]. Most of the reported work in [3,4,5,6] on multiple antenna structure work is limited to the frequency band for 2G/3G/4G. Accommodating multiple antennas at the low-frequency band is a daunting task on a limited footprint area of a smartphone due to the transfer of power among ports. To counter this difficult task, the World radio conference 2015 (WRC-2015) allocated new frequency bands for 5G cellular technology consisting of sub-6 GHz or below 6 GHz The MIMO performance measures, such as envelope correlation coefficient (ECC), mean effective gain (MEG), and MIMO channel capacity, and customer’s hand effect are studied extensively for the proposed multiple antenna system
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