## 3 Design Procedure
#### (b2) Dielectric substrate material
The first antenna model (REF1) reproduces linear polarization while the second one (REF2) reproduces the circular polarization. The circular polarization is obtained through the introduction of the diagonal slot into the patch layer. Both principles of operation are achieved via a single antenna configuration when a CC is added. The models and prototypes of the reference antennas are shown in Figure 10.  
The simulated and measured performance characteristics of both antennas are shown in Table 6. Regarding the REF1 antenna, the observed difference in the resonant frequency is mainly attributed to the fact that the antenna prototype length is found to be shorter (by 0.5 mm) than the numerical one. A slight increase in impedance bandwidth may reveal increased textile substrate losses of the prototype antenna compared to the simulated model. Furthermore, the axial ratio at the operating frequency seems to degrade, mainly,  
Figure 10: Models (**top**) and prototypes (**bottom**) of REF1 (**left**) and REF2 (**right**). due to measurement imperfections and antenna positioner effects that are not counted in simulations. Still, the axial ratio of the prototype is acceptable and yields a clear LP. Furthermore, the measured far-field gain is decreased which can indicate two matters: the prototype presents extra losses than simulations, and the measurements unavoidably cause errors due to various factors that will be described in Section 4. Still, the gain value is suitable for off-body communication. Further, the numerical and measured radiation efficiencies are quite close. Similar observations can be deduced for the REF2 antenna. It is apparent that the measured axial ratio is at the limit of 3 dB. This occurs due to slight differences in the fabricated dimensions of the diagonal patch slot. Overall, both reference antennas yield satisfactory performance results without considerable deviations between simulations and measurements. This design step allows us to figure out design and fabrication issues prior to the implementation of a CC that may cause perturbations in the antenna structure. Actions that can be realized to overcome potential issues are: re-measurement of dielectric substrate losses taking into account possible use of an adhesive material, re-fabrication of prototypes with more accurate techniques to achieve precise antenna dimensions, and elimination of measurement errors. It should be outlined that as long as the textile antenna requirements are met despite potential discrepancies between simulations and measurements, the re-adjustment of the reference antenna model is optional. (d) CC antenna initial design and modeling  
In this step, the clothing component that has been selected in the concept selection step is taken into account within the design process evolving the reference antenna. This means that the antenna model is designed by integrating the CC into its structure. To accurately simulate the CC textile antenna and evaluate its performance properties, the CC needs to be geometrically modeled in detail. CC antenna performance may differ from the REF antenna's resonance and radiation behavior. On that occasion, the CC antenna design needs to be re-adjusted to achieve the requirements settled in step (a) and fulfilled by the REF model. In Figure 11, the side view of a REF textile patch antenna that uses shorting pins and the side view of a CC antenna that applies snap-on buttons instead of pins are depicted. In Table 7, a performance comparison between the two antenna models is recorded. Based on the simulated results, minor deviations are observed between the antenna models. Therefore, there is no need for design re-adjustment of the CC antenna. Here, it should be highlighted that the design of the initial antenna model using shorting pins in place of the geometrically complex snap-on buttons considerably saves valuable computational time until the desired application requirements are accomplished. Then, the CCs can be used by applying a light design optimization scheme.