# A Compact Wearable Textile Antenna for NB-IoT and ISM Band Patient Tracking Applications
A wearable dual-band multi-layer patch antenna was proposed in [15]. However, this work did not evaluate specific absorption rate (SAR) and bending analysis. Another wearable antenna for brain monitoring applications was reported in [16]. This antenna was non-textile with footprints of 70 mm \(\times\) 30 mm and operated in the ISM 2.4 GHz frequency band. A low-profile textile-based antenna system was presented in [16] for body temperature and sweat sensing with an antenna size of 68 mm \(\times\) 68 mm. Another low-profile multi-band textile circular patch antenna was reported in [17]. A compact single-band antenna (ISM 5.8 GHz) with a limited ground plane and low SAR value was proposed in [18]. A wearable textile quasi-Yagi antenna functioning in dual frequency bands (0.868 GHz and 2.45 GHz) was proposed in [19]. The area of this antenna was 65 mm \(\times\) 60 mm, and the gain was relatively low (\(-\)1.4 dBi). A high-gain and high-profile (multi-layer substrate) textile antenna working in dual frequency bands (2.45 GHz and 3.45 GHz) of area \(0.49\lambda_{0}\times 0.49\lambda_{0}\) was reported in [20]. A narrowband and low-gain textile antenna working in multiple frequency bands was presented in [21]. One more antenna designed for military applications, functioning at 8 GHz, was explained in [22]. However, this antenna had a large size and low gain of 5.2 dBi. A multiband textile antenna with the ultrawideband (UWB) was proposed in [23] with a gain of 7.2 dBi. A single ISM 2.4 GHz textile antenna was proposed for wearable applications [24]. The antenna's gain was 5.4 dBi, but the authors did not perform bending and SAR analyses. An ultra-high frequency (UHF) antenna for RFID applications was proposed in [25], and the antenna was embroidered on a surgical mask. This antenna showed wide bandwidth at the UHF frequency, which makes it suitable for wearable applications. Table 1 compares previously reported wearable textile antennas with the proposed antenna. At present, healthcare technology requires wide bandwidth multiband antennas with optimum on-body gain for effective communication to the outside-body devices in all bending scenarios. Another textile antenna of size \(0.43\lambda_{0}\times 0.43\lambda_{0}\), working in the single frequency band (2.45 GHz), was explained in [26]. This antenna had a gain of 6.3 dBi and a bandwidth of 6.6%. One more antenna for RFID tags in the UHF band was proposed in [27] and worked only in the single resonance with a peak gain of \(-\)7.1 dBi. Embroidery-based antennas are also a decent option for wearable applications. However, all the embroidery antennas have some limitations, such as antennas being unable to use high-resolution designs, conducting threads used to realize the antenna having high resistivity compared to metal materials, and parasitic capacitances forming between the threads. Due to these reasons, some characterizing and optimizing techniques were proposed [28] to improve the behavior of these antennas. In order to obtain stable behavior from the wearable antennas, they must have the following properties, as discussed in [29]:  
* The antenna should withstand different physical impacts related to regular usage;* Multiband behavior is needed to support numerous applications;
* The wearable antenna must be small-sized, flexible, lightweight, and comfortable on the body. Wearable antennas discussed in [10; 11; 25; 27] were single-band antennas, and the antenna discussed in [11] was a single-band large-sized antenna. Multiband antennas were reported in [8; 9; 12; 13; 21], but antennas proposed in [8; 9; 21] had limited/narrow impedance bandwidth and antennas in [12; 13] had large footprints. In [21], the gain in all the reported frequency bands was on the lower side, and the authors did not perform a bending analysis of the antenna to prove its usefulness in a natural environment. The high-profile antennas (multi-layer) were discussed in refs. [20; 26]. Also, the antenna designed in ref.