## 2 Clothing Components in Wearable Textile Antennas
### Velcro  
A limited number of research works that apply the Velcro CC as an active part of WTAs have been recorded in the literature. A lot of researchers though have used Velcro tapes as a means of integrating wearable antennas into the garment. This differentiation can arise from the fact that non-conductive and conductive Velcro tapes can be found in the textile market. The non-conductive tape can be mainly used for antenna integration. Still, it can be used as part of the antenna to facilitate interconnection with a textile feed line, as shown in [47]. Specifically, in this work, the use of a plastic Velcro enables an all-textile connector for a textile patch antenna. On the other hand, the conductive Velcro can be successfully used as a functional part of wearable textile antennas, as proposed in [48]. The use of Velcro tapes provides polarization and frequency reconfigurability into the patch antenna. The Velcro-base (hooks) has been sewn with a non-conductive yarn onto the patch layer providing mechanical stability. It should be noted that slight degradation in the antenna radiation efficiency has been noticed due to the ohmic losses of the conductive Velcro. Furthermore, the conducted repeatability measurements proved a stable antenna performance. Based on the research works, it seems that the Velcro as a CC used in WTA is quite user-friendly, adequately satisfying the wearability requirements.  
In Table 3, details of the Velcro-based patch antenna designs are presented. In Figure 3, a photo of the textile patch antenna described in [48] is shown revealing the great potential and easiness of Velcro use for antenna structural reconfiguration.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & **Type/** & **Dimensions (mm)** & \multirow{2}{*}{**App.**} & \(\mathbf{\ell_{c}}\) & **BW** & \(\mathbf{e_{rad}}\) & **Gain** \\  & **Radiation** & & **L, W, H** & **(GHz)** & **(GHz)** & **(\%)** & **(dBi)** \\ \hline \multirow{2}{*}{[42]} & Circular Patch/ & 23.4, 23.4, 3.5 & \multirow{2}{*}{ISM/WLAN} & 5 (CP) & 0.5 & \multirow{2}{*}{N/A} & \multirow{2}{*}{N/A} \\  & Broadside & (40 \(\times\) 40 \(\mathrm{GND}\)) & & 4.7 (Slot) & 0.6345 & & \\  & & & 5.2 (No-Slot) & 0.494 & & \\ \hline \multirow{2}{*}{[43]} & Patch/ & 18.5, 19.5, 3.5 & \multirow{2}{*}{ISM} & 3.62 & 0.1 & \multirow{2}{*}{N/A} & \multirow{2}{*}{N/A} \\  & Broadside & (40 \(\times\) 40 \(\mathrm{GND}\)) & & & & \\ \hline \multirow{2}{*}{[44]} & PIFA or Patch/ & 23, 20, 3.2 & \multirow{2}{*}{ISM/WLAN} & 2.45 & 0.093 & 30–90.2 & –0.9–5.9 \\  & Broadside & (60 \(\times\) 55 \(\mathrm{GND}\)) & & 5.8 & 0.234 & 80.4–88.7 & 8.1–8.4 \\ \hline \multirow{2}{*}{[45]} & PIFA/ & 26, 22, 3.2 & \multirow{2}{*}{ISM} & 2.82–2.94 & 0.071–0.153 & 29.8–93.7 & –1.07–7.37 \\  & Broadside & (60 \(\times\) 50 \(\mathrm{GND}\)) & & & & \\ \hline \multirow{2}{*}{[46]} & CMSIC/ & 120, 79.7, 32 & \multirow{2}{*}{ISM} & \multirow{2}{*}{2.45} & \multirow{2}{*}{N/A} & OFF:82.7 & OFF:9.2 \\  & Omni-broadside & (120 \(\times\) 120 \(\mathrm{GND}\)) & & & & ON:77.1 & ON:3.8 \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._  
Figure 2: (a) Foldable patch module (dimensions in mm). The white dash lines indicate the radiation element folding positions for the 9 and 10 GHz configurations; (b) prototype module realizations. “Reprinted/adapted with permission from Ref. [40]. © 2016, © Shengjian Jammy Chen”.