# Wideband-Narrowband Switchable Tapered Slot Antenna for Breast Cancer Diagnosis and Treatment
## 1 Introduction  
Breast cancer treatments are being developed rapidly to reduce the dangerous radiation associated with conventional methods [1]. The early detection of breast cancer has received significant attention among research groups, and common techniques are based on X-rays, magnetic resonance imaging (MRI), and computer tomography (CT) [2]. However, these techniques have numerous drawbacks such as ionizing radiation, high cost, health risks, and so on. Radar-based microwave imaging is an effective tumor detection method. In this method, malignant tissues within the breast can be detected because of significant differences in the dielectric properties between normal breast cells and tumor cells. These images can be produced by employing ultra-wideband (UWB) antennas [3; 4; 5; 6; 7]. These antennas transmit and receive short-duration pulses and detect the scattered signal differences between normal and malignant tissues. The surgical operation, radiotherapy, chemotherapy, and hyperthermia are the main methods to treat breast cancer. Among these, a microwave hyperthermia system for cancer treatment is reliable, non-invasive, cost-effective, and painless in comparison to surgical operations. Furthermore, hyperthermia has a synergistic effect when used in combination with radiation oncology or chemotherapy. Non-invasive hyperthermia, which employs a microwave antenna, is a reliable treatment method to achieve effective breast tumor necrosis [8]. In this method, electromagnetic energy (EM) is radiated from a narrowband antenna and concentrated on the tumor region, where heating is applied as a therapeutic treatment [9; 10; 11]. However, as the microwave diagnosis system operates separately from the treatment system, the process is complicated, time-consuming, and expensive. The integration of these two systems simplifies the process and provides a comfortable treatment environmentfor patients. To implement such an integrated system, the characteristics of the two different systems must be incorporated into a single antenna. However, as the allocated wideband frequency for microwave imaging and narrowband frequency for hyperthermia are different, frequency reconfigurable characteristic is essential for the antenna. Frequency reconfigurable antennas have been investigated widely in terms of switching the wide- to narrowband with PIN diode switch. The research of wideband to narrowband switching antennas was presented over past years [12; 13; 14; 15; 16; 17]. In [12], the ring slot resonators were perturbed in the antenna feed line with PIN diodes. In [13; 14], the frequency notched and narrowband characteristics were realized by applying the ring slots and split ring resonators (SRR) in the feeding area. In [15; 16], the C-, T-shaped slots and ring slots were notched on the flared slot of a tapered slot antenna (TSA) for wide to multiband switching. In [17], the C-slot patch antenna was designed on the dual patch element in order to achieve reconfigurability. In these papers, however, as the narrowband structures for frequency switching were inserted directly on the antenna surface or feeding area of the wideband antenna, the wideband performances of the antenna degraded, and the design complexity increased because at least two PIN diodes were used to obtain frequency switching and wideband characteristics. Furthermore, the narrowband structure must be compact in size to minimize interference with the wideband antenna. However, existing narrowband structures are electrically large because of the resonance length of their operating frequencies. In this paper, a wideband to a narrowband switchable antenna with a compact meander line resonator was proposed for an integrated microwave imaging and hyperthermia system for breast cancer detection and treatment. The conventional wideband TSA is designed to operate in the 3.1-10 GHz (UWB) frequency band for microwave imaging. The narrowband operation for hyperthermia can be achieved with meander line resonators with a PIN diode switch.