## 3 Design Procedure
#### (b2) Dielectric substrate material  
Commercially available fabric materials such as felt, denim, and cotton are commonly used in wearable textile antennas. The dielectric properties of these materials are not usually known, therefore, they need to be measured since their electric behavior significantly affects antenna performance. The dielectric constant, \(\varepsilon_{r}\), and loss tangent, \(\tan\), are the critical parameters to be determined. Various experimental techniques can be used for the measurement of the dielectric properties including Split Post Dielectric Resonator (SPDR), Nicholson-Ross-Weir (NRW), Microstrip stub line, and other methods, as analytically described in [56]. Even if the dielectric values are provided by the suppliers, the textile parts that will be used for antenna fabrication still need to be measured since such materials are usually not homogeneous and their properties can spatially vary. In order to prove this statement a commercial white felt is cut into two orthogonal pieces along different directions A and B as shown in Figure 7. The aim is to measure the dielectric properties  
Figure 6: Microstrip patch antennas applying different conductive materials: (a) copper tape (\(\sigma=5.8\times 10^{7}\) S/m); (b) conductive embroidered yarn (\(\sigma=1.1\times 10^{4}\) S/m). using multiple dielectric parts, we suggest using textile parts along the direction which yields more stable properties. _(b3) Clothing component materials_  
Commercial clothing components such as Velcro tapes, zip fasteners, buttons, and snap-on buttons can be made of conductive and non-conductive materials. Regarding the conductive Velcro and zip accessories, their electric properties are usually given in terms of surface resistivity and their respective conductivity can be calculated. In Figure 9, Velcro tapes metalized with 99.9% pure silver and fully silver-plated zippers are presented. Due to their electrical conductivity, novel application capabilities can occur in smart textiles. The buttons and snap-on buttons are made of standard commercial metals (e.g., copper and brass) and their conductivity can be found in the literature. In the case of non-conductive CCs, the buttons and snap-on buttons are usually made of known polyester with specific properties. Furthermore, commercial Velcro tapes are made of polyamide or polyester. The non-conductive zips are made of polyester or nylon. The non-conductive CCs are usually homogeneous and bulk; still, they maintain stable properties. All non-conductive CCs properties need to be estimated and calculated as in (b2). Reference antenna design model is a quite critical step throughout the design procedure. The targets of this step are: (i) the creation of an antenna design model as a reference one without the use of clothing components, (ii) evaluation of the properties of the textile materials, (iii) comprehension of the proposed antenna concept, and (iv) determination of the effect of realistic factors such as the SMA connector effect. The tasks that can be performed in this step are: design and simulation of the reference antenna/s (REF) to conduct the desired operation and fabrication of an antenna prototype to evaluate the numerical estimation, the properties of the applied textile materials, the realistic factors and the principle of operation of the specific antenna. To unravel this design step, two reference antenna design models and their fabricated prototypes, which have been presented in [48], are employed. The antenna concept was to  
Figure 9: Conductive Velcro tape and Zip fastener from Shieldlex, Bremen, Germany (www.shieldlex. de, accessed on 2 March 2023). develop a textile microstrip patch antenna that presents polarization reconfiguration by applying a CC as a passive reconfiguration means for off-body wireless applications. Felt material is used for the dielectric substrate, while, the patch and ground layers are made of conductive electrotextile (Nora-Dell).