## 2 Antenna Configuration  
To design a flexible, miniaturized, wearable UWB antenna, a substrate with a high dielectric constant and low loss tangent can be utilized (the dielectric constant of the flexible antenna's substrate should be close to the breast's relative permittivity to have excellent coupling between the antenna and the breast [3; 42]. This improves the scattering parameters of the antenna). The proposed antenna design is arrived at after designing the conventional patch and enhancing gain and BW using techniques such as photonic band gap (PBG) structures and substrate integrated waveguide (SIW) (Figure 1). In all steps of designing the antenna, the dimensions and patch are optimized to obtain the best results. Figure 2 and Table 1 show the simulation and measurement setup. Figure 1: (**a**,**b**) Simulated prototype of the proposed antenna: (**a**) front view and (**b**) back view and the full ground, (**c**) substrate-integrated waveguide (SIW) feeding transition, and (**d**) loading with shorting pins and photonic band gap (PBG) structure. Figure 2a depicts the general concept of the simulation setup of the proposed antenna. It demonstrates that the antenna touches the breast and then the scattering data are recorded by a vector network analyser (VNA). Afterward, the data extracted from VNA and imported to a PC to reconstruct the image of a tumour in breast using an algorithm. Figure 2b,c indicates the front view of the fabricated prototype of the antenna and the measurement setup of the antenna on chest, respectively. It should be mentioned that the antenna is pasted on the shirt not to move during the measurement. Figure 2d shows the measurement setup of the antenna located on a breast phantom. This phantom is 3D printed using elastic PLA material considering almost the size of a \(E\) size female breast. During the antenna optimization, size alteration of each design parameter in the antenna design procedure affects the antenna characteristics such as surface current distribution (SCD) shown in Figure 3. This happens because each change alters the surface current distribution of the antenna and so as the electromagnetic fields around it. Analysing \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameters (mm)** & **Values** & **Parameters (mm)** & **Values** & **Parameters (mm)** & **Values** \\ \hline W\({}_{\text{s}}\) & 50 & \(W_{1}\) & 13 & \(r_{2},t_{2}\) & 0.5, 3 \\ L\({}_{\text{s}}\) & 60 & \(L_{1}\) & 19.75 & \(r_{3},t_{3}\) & 3.35, 2.8 \\ W\({}_{\text{P}}\) & 29.5 & \(a\) & 1.8 & \(r_{4},t_{4}\) & 1.8, 1.4 \\ L\({}_{\text{P}}\) & 29.5 & \(b\) & 26 & \(r_{6},t_{6}\) & 1.4, 0.7 \\ \(r_{1},t_{1}\) & 4.5, 1.5 & \(r_{5},t_{5}\) & 1.5, 0.75 & 2.76, 1.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Antenna parameters dimensions. Figure 2: (**a**) Simulated human female voxel model and simulation setup, (**b**) the fabricated prototype of the antenna, (**c**) measurement setup on chest, and (**d**) the measurement setup on breast phantom. these behaviours illustrates how each variation in these parameters affects the antenna characteristics. Therefore, the SCD is investigated at different frequencies such as 3.4 GHz (5G), 5.7 GHz (sub-6 GHz), 7 GHz (lower-end of the BW), 15 GHz, and 28 GHz (higher-end of the BW). It shows that the current is stronger around the feeding and the slot that separates the patch from the CPW slot at 3.4 GHz. it is noticed that this current is stronger around the EBG structures and the arc shape slots, which were added to extend the BW at the lower band (7 GHz) and make the stopbands occurred around 12.5 and 16.5 GHz to passbands. Besides, it depicts that the current is stronger and has more density around the CPW slot and the feeding at the lower-end and higher-end of the operating BW. There has been in-depth study of various periodic structures in microstrip lines, including photonic bandgap (PBG), electromagnetic band gap (EBG), and defected ground structure (DGS) [43]. These three periodic structures each have their own properties and advantages.