# Defining Breast Tumor Location Using a Four-Element Wearable Circular UWB MIMO Antenna Array
## 4 Results and Discussion  
### Tumor Detection Results  
The primary objective of this section is to detect and localize tumors within the glandular tissue of the human breast, as this is where breast cancer typically originates, and early detection in this region can help to prevent its spread. The following steps were taken to achieve this goal. Step 1 involved operating the proposed system on healthy breast tissues without tumors and measuring the scattering coefficients of the four suggested antennas. These coefficients were then compared with the scattering coefficients obtained from unhealthy tissues containing tumors. In Step 2, the glandular layer of the hypothetical breast was divided into four quadrants (I, II, III, and IV). A tumor was simulated only in the first quadrant of the proposed system, and the S-parameters were recorded for analysis. Step 3 focused on moving the tumor from the first quadrant to the second quadrant, simulating the system accordingly, and recording the outcomes. Four simulations were conducted for each of the four tumor sites (P1 in quadrant I, P2 in quadrant II, P3 in  
Figure 8: (**a**) Perspective view without a cavity, (**b**) top view without a cavity, (**c**) top view with Dacron cavity, and (**d**) side view with Dacron cavity of the detection system. quadrant III, and P4 in quadrant IV). Figure 9 illustrates the locations of the tumors and the phantom quadrants. Table 6 and Figure 10 present the reflection coefficient and coupling coefficients (S11, S21, S31, and S41) for healthy breast tissue and the four tumor locations in unhealthy tissue, respectively. It is important to note that the proposed scenario always searches for the first minimum in the reflection and coupling coefficients. The frequencies F1 and F2 of the first minimum are determined and compared using the detection parameter \(\aleph=\mathrm{F_{1}}/\mathrm{F_{2}}\). If \(\aleph<1\), it indicates the absence of a tumor, as depicted in Figure 10a, where \(\mathrm{F_{1}}=2.81\) GHz, \(\mathrm{F_{2}}=2.88\) GHz, and \(\aleph<1\). If \(\aleph\geq 1\), the presence of a tumor is confirmed, and the localization stage follows. In the localization stage, antenna 1 transmits signals, while the other three antennas receive signals. By examining the coupling coefficients S21 and S41 for the first minimum and considering the 45 dB line as a reference, the position of the tumor can be determined. When the tumor aligns with antennas 1 and 3 and crosses the reference line, as shown in Figure 10b,d, the antenna system is rotated around the breast until this alignment occurs. Once the alignment is achieved, antennas 1 and 3 stop transmitting or receiving signals, and antenna 2 begins transmitting, while antenna 4 receives. By assessing the coupling coefficients between antennas 2 and 4 and observing their alignment with the tumor, along with the 50 dB line as a reference, the tumor position is detected. If the reference line is never crossed, the tumor is aligned with antennas 2 and 4, as seen in Figure 11h. By following this detection and localization approach, the proposed system can effectively identify the presence and position of tumors within the glandular tissue of the human breast. A flow chart of the detection scenario is shown in Figure 12. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**No**} & \multicolumn{4}{c}{**Tumor Positions**} \\ \cline{3-6}  & **Tumor** & **P1** & **P2** & **P3** & **P4** \\ \hline Detection parameter & \(\aleph<1\) & \(\aleph>1\) & \(\aleph>1\) & \(\aleph>1\) & \(\aleph>1\) & \(\aleph>1\) \\ \hline S11 (dB @ GHz) & 18.8 @ 2.8 & 17.47 @ 2.82 & 15 @ 2.83 & 17.55 @ 2.82 & 13.7 @ 2.83 \\ \hline S21 (dB) & 48.8 @ 2.9 & 54.56 @ 2.78 & 40 @ 2.78 & 54.8 @ 2.78 & 40 @ 2.78 \\ \hline S31 (dB) & 43.8 @ 2.9 & 41.5 @ 2.78 & 35 @ 2.78 & 41.5 @ 2.78 & 35 @ 2.78 \\ \hline S41 (dB) & 48.8 @ 2.9 & 54.56 @ 2.78 & 40 @ 2.78 & 54.8 @ 2.78 & 40 @ 2.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The five cases’ reflection coefficients.