# A Compact Wearable Textile Antenna for NB-IoT and ISM Band Patient Tracking Applications
[26] is a single-frequency band antenna; however, the wearable antennas have to communicate to implants and external antennas, so it is necessary to have at least dual-band functioning. However, wide impedance bandwidth causes the antenna's frequency bands to be unaffected by detuning caused by bending due to the curvature of the human body and its movement. However, the research work proposed in [19; 23; 27] did not consider SAR analysis, a critical parameter in the design of antennas for wearable applications. It identifies the safe input power value given to the antenna while working on the wearer's body. Therefore, a compact, multiband antenna with good gain and wideband behavior must be designed. The multiband antenna enables data transfer, power transfer, and control signaling or data transfer at multiple data rates or can support different frequency applications. Also, a high-gain and wideband antenna enables wide-range tracking and makes the antenna immune to detuning in various bending environments. Thus, keeping all the above factors in mind, a wearable textile monopole antenna is proposed on a denim fabric substrate with a volume of 60 mm \(\times\) 60 mm \(\times\) 1 mm for patient tracking in this paper. The proposed antenna works in the narrow band-internet of things (NB-IoT), RFID, and ISM 2.45 GHz/5.8 GHz frequency bands. NB-IoT technology offers long-range communications at a low-data rate for wearable sensors with a long battery life [30]. Meanwhile, 2.45 GHz and 5.8 GHz bands are used for RFID patient tracking applications because these bands are entirely safe for the human body, as per the Federal Communications Commission (FCC). The impedance bandwidths at 1.8 GHz, 2.45 GHz, and 5.8 GHz are 330 MHz, 780 MHz, and 900 MHz, respectively. Therefore, the proposed multiband antenna can use one frequency band for patient tracking (ISM RFID 2.4/5.8 GHz), and the other frequency band can support different applications. Also, the on-body gain values of the antenna are 3.7 dBi, 5.3 dBi, and 9.6 dBi, at 1.8 GHz, 2.45 GHz, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref. (Year)** & [19] & [20] & [21] & [22] & [23] & **This Work** \\ \hline Area (mm\({}^{2}\)) & \(65\times 60\) & \(60\times 60\) & \(60\times 60\) & \(55\times 40\) & \(84\times 69\) & \(60\times 60\) \\ \hline Area (\(\lambda_{0}\)\({}^{2}\)) & \(0.18\times 0.17\) & \(0.49\times 0.49\) & \(0.64\times 0.64\) & \(1.46\times 1.06\) & \(0.55\times 0.67\) & \(0.36\times 0.36\) \\ (\(\lambda_{0}\)\({}^{2}\)) & (0.03) & (0.24) & (0.41) & (1.55) & (0.37) & (0.13) \\ \hline Frequency (GHz) & \(0.868/2.45\) & \(2.45/3.45\) & \(2.4/3.32/3.93/5.8\) & \(8\) & \(2.4/5\) & \(1.8/2.45/5.8\) \\ \hline B.W. (\%) & NG/3.5 & \(4.9/6.7\) & \(\begin{array}{c}3.7/5.7/\\ 5.85/9.8\end{array}\) & \(13.1\) & \(5/76\) & \(17.2/39.1/19.6\) \\ \hline Peak gain (dBi) & NG/ –1.4 & \(6.7/8.9\) & \(-0.81/-2.81/-1.16/2.8\) & \(5.2\) & \(7.2\) & \(3.7/5.3/9.6\) \\ \hline SAR (W/Kg) 1 gm/10 gm & NG & \(\begin{array}{c}0.1/0.04\\ (\text{at }0.5\text{ W})\end{array}\) & \(\begin{array}{c}0.11/0.33\\ (\text{at }1\text{ W})\end{array}\) & \(\begin{array}{c}0.7/\text{\,--}\\ (\text{at }1\text{ W})\end{array}\) & NG & \(\begin{array}{c}0.0796/0.0759\\ 0.0575/0.0552\\ 0.0226/0.0204\end{array}\) \\ \hline \hline \multicolumn{7}{c}{Note: NG—Not Given.} \\ \hline \end{tabular}
\end{table} 
Table 1: Proposed antenna and previously reported textile antennas. and 5.8 GHz, respectively. The proposed antenna is designed on the multi-layer cuboid phantom to be compatible with patient tracking, with the thickness of skin, fat, and muscle to be 4 mm, 8 mm, and 25 mm, respectively [31], as shown in Figure 1. Each layer has dielectric properties as per Ref. [32]. The antenna's geometry is a stepped square planar monopole antenna with asymmetric meandering slots. The ground plane is partial with slots and stubs, which helps to create boresight radiation in all the reported frequency bands.