Design and Analysis of UWB MIMO Antenna for Smart Fabric Communications

Abstract

This paper presents a flexible multiple-input, multiple-output (MIMO) antenna with ultrawideband (UWB) performance for smart clothing applications. The MIMO antenna is comprised of four octagonal-shaped radiators with several slots loaded into them, and it offers a frequency range of 2.9–12 GHz. The unit cell has a size of 0.26λ0 × 0.164λ0 × 0.014λ0 and the MIMO antenna has a size of 0.48λ0 × 0.48λ0 × 0.014λ0, where λ0 corresponds to the lowest operating frequency. The radiation and diversity performances of the antenna are evaluated, and the obtained metrics are envelope correlation coefficient (ECC) <0.045, diversity gain (DG) >9.9 dB, total active reflection coefficient (TARC) <−14 dB, and channel capacity loss (CCL) <0.13 bits/s/Hz. The bending analysis of the MIMO antenna is performed. The specific absorption rate (SAR) of the MIMO antenna is also investigated, and the obtained values are 0.229 W/Kg (4 GHz), 0.253 W/Kg (7 GHz), and 0.463 W/Kg (10 GHz).

Low-Profile UWB-MIMO Antenna System with Enhanced Isolation Using Parasitic Elements and Metamaterial Integration

“…The diversity gain (DG) is used in MIMO-system gain enhancement and gives insight into the effects of the diversity on the wireless links. It is calculated using Equation (4) [41]:…”

“…It depends on the antenna S parameters and defines the return loss in the MIMO antenna. For the case of a two-element MIMO antenna, it can be estimated using the following equation [35,41], in which an ideal value of zero is desired:…”

“…For a better performance, the CCL must be less than 0.4 bits/Hz/s [36,37]. It is calculated using the S parameters using Equations ( 6)-( 8) [36,39,41]:…”

Decoupling Methods in Planar Ultra-Wideband Multiple-Input-Multiple-Output Antennas: A Review of the Design, State-of-the-Art, and Research Challenges

“…Various DTs to reduce mutual coupling are presented in the literature. For example, placing AEs at 90 • [37][38][39][40][41][42][43][44][45][46] and 180 • [47][48][49], introducing DS [50][51][52][53][54][55][56][57][58][59], NL [60,61], DGS [62][63][64], metamaterial [65][66][67], PE [68][69][70], CBF [71], and SES [72].…”

“…The AE was further developed into a MIMO antenna configuration with four elements placed orthogonally to each other in a single plane. In paper [44], the MIMO antenna was composed of four octagonal-shaped radiators with several slots loaded into them, which were placed orthogonally, as displayed in Figure 2h. In [45], the AE consisted of a circular patch that offers better impedance matching over the UWB range without the use of a feeding line, as shown in Figure 2i.…”