# Dual-Band MIMO Antenna for n79 and sub-7 GHz Smartphone Applications
###### Abstract
Several MIMO antennas with good isolation for 5G smartphones are recommended in the literature, including multiple antennas with low proximity [14; 15], compact size antennas [16], and multiband MIMO antennas using monopole [17], dipole [18], and patch antennas [19; 20]. However, the main drawback of such systems is that they possess higher local conversion coaxial [10; 19] or deteriorated radiation characteristics [10; 21] and involve higher complexity of design. In the work of [22], the design of a \(10\times 10\) dual-band MIMO antenna with a neutralizing line decoupling structure is demonstrated. However, its efficiency is poor at 45% and it provides isolation of only 12 dB. As described in [23], an effective low-profile frequency reconfigurable MIMO antenna is designed for dual-band application using a varactor diode. This antenna was designed such that it can also control the output frequencies in the range of 1.7 GHz to 3.8 GHz for both bands at once. However, due to the nonlinear nature of a varactor diode, its fabrication process may become cumbersome and it also has a direct bearing on the radiation characteristics of an antenna. On the other hand, Ref. [24] presented a wide-band antenna for 5G within the sub-6 GHz bands using hexagonal split-ring resonators operating between 2.85 and 5.35 GHz with a 50% impedance bandwidth, but which suffers from an SRF split-ring resonator structure and native metal loss impacting the radiation efficiency of the antenna. These are some of the most commonly found methodologies for antenna designs especially for MIMO systems. But the search goes on for a multiband, independently tunable MIMO antenna with high radiation efficiency and port isolation, which is more demanding for 5G handsets utilizing the C-band. Using the method of independent frequency control, a comprehensive parametric analysis was carried out to define assorted parameters. Moreover, a 10-element MIMO antenna array was developed and experimentally characterized to prove the design concept. The outcomes of this experiment show that the design mentioned in this paper provides outstanding results with high isolation greater than 17 dB. The antenna array also has peak efficiencies of 64% and 71%, and gains of 2.8 dBi and 6.2 dBi for the lower and upper operating frequencies, respectively. However, the novelty of this work is the design of open-ended scissor-shaped antennas with partial ground to achieve the n79, n102, and n104 frequency bands with connected ground for next generation applications. As well as these parameters, the MIMO antenna was also analyzed for diversity gain, and to determine the envelope correlation coefficient. These two parameters indicated that the design achieved near-perfect MIMO performance. The remainder of the article is organized as follows: Section 2 explains the steps involved in the design of the antenna and describes the geometry of the antenna in more detail. In section 3, the s-parameters, radiation patterns, and MIMO parameters of the dual-band antenna are presented and analyzed with equally detailed consideration given to both the simulation and experimental results. Last of all, Section 4 of the article summarizes the entire study and the research findings.