# Wideband-Narrowband Switchable Tapered Slot Antenna for Breast Cancer Diagnosis and Treatment
## 3 Simulation and Measurement Results
Especially for microwave systems, the fidelity factor value must be over 0.5 [3]. The calculated fidelity factor for the proposed TSA was 0.95. This was a reliable result, which confirmed the suitability of the proposed TSA for microwave imaging systems. The experimental setup for the time-domain signal acquisition is presented in Figure 13. The dielectric permittivity of a breast cancer cell is almost 10 times larger than the dielectric permittivity of a normal breast cell [18]. A cylindrical cancer cell in the middle of the breast phantom is presented in Figure 13a, the radius of which is 5 mm. As a result of the difference between the dielectric permittivities, a scattering effect occurred when the E-field passed through the breast phantom. The differences of the backscattered time-domain signals, which were measured both with and without a cancer cell, are presented in Figure 14 for reflected and transmitted signals. The UWB signal was radiated using a stepped  
Figure 12: (**a**) Simulation configuration to verify the pulse distortion characteristic and (**b**) radiated and received pulse characteristics. frequency sweep, and the backscattered signals reflected from the tumor were collected by the receiving antennas at different locations. For each position, the recorded signals from the tumor reflection could be extracted from the overall signal by subtracting the original signal. The collected, scattered signals were converted to the time domain signal by the inverse Fourier transform and applied to an imaging algorithm developed by [7]. When the transmitted signal progresses over time, the skin reflection was identical in both cases. Therefore, the scattered signals between the tumor cell and homogeneous breast phantom were recorded by the receiving antennas, and these signals were used to infer the existence and location of the arbitrary target. The detected signal differences shown in Figure 14 could be calculated and applied to the UWB multi-static radar-based microwave imaging system to define the tumor cells. To operate as a hyperthermia system, Figure 15 shows the required configuration of the temperature measurement setup, block diagram of the temperature measuring system (which was composed of the RF signal generation and amplification, as well as RF power division and excitation), and the temperature observation [9; 10]. The proposed antenna must exhibit equal polarization characteristics to achieve an effective E-field synthesis in the target area. For hyperthermia application, the specific absorption rate (SAR), which is proportional to the square root of the E-field, is analyzed to verify the radiation characteristics in the breast phantom [9]. In Figure 16a, the variation of the normalized SAR with the number of antennas is presented to verify the EM energy concentration at the center of the breast phantom (x = 0 mm), from which it was evident that the SAR increases  
Figure 14: The difference of the backscattered time domain signal (a) reflected scattering signal, and (b) transmitted scattering signal. Figure 13: (a) Configuration of the backscattered signal measurement setup, and (b) picture of the experimental environment. by increasing the number of antennas to the target position. To verify the thermal effect for tumor necrosis, the effective treatment area (ETA) was defined [9]. The ETA was regarded as a region in which the tumor satisfied the thermal requirement of the temperature rise, 7-10 \({}^{\circ}\)C. The temperature increase measured inside the breast phantom, heated by a 12-array antenna for 1 h, is shown in Figure 16b. The red circular region signifies the ETA, which covers the tumor size.