# Modified 16-Quasi Log Periodic Antenna Array for Microwave Imaging of Breast Cancer Detection
## 1 Introduction  
Women die from breast cancer more often than any other cancer worldwide. Breast cancer develops in a very complex way, involving multiple cell types, and prevention of the disease remains a challenge. Early detection of breast cancer can greatly reduce the possibility of its progression. Breast cancer patients in some developed nations have a 5-year survivorship of more than 80% due to early detection and treatment [1]. For detection of breast cancers, various imaging technologies, such as ultrasound, X-ray, Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and nuclear medicine imaging, have been developed over the last decades [2]. As of now, microwave imaging is a promising technique to identify abnormalities in the human body based on the electrical characteristics of both healthy and malignant tissues. As opposed to other medical imaging methods, microwave imaging is characterized by the fact that it is low in complexity, low in cost, and does not generate ionizing radiation. Several ultra-wideband (UWB) antennas for Microwave Imaging System (MIS) have been proposed in recent decades, including the slotted antennas [3; 4; 5], dipole antenna [6], coplanar waveguide (CPW) antenna [7], vivaldi antennas [8; 9; 10], Vee dipole [11], EBG antenna [12], tunable antenna [13], and resistively loaded bowtie antenna [14]. The antenna is a significant piece of equipment that collects signals from adjacent scattered objects or sends signals to nearby objects. The performance of a MIS is mostly determined by the antennas that are employed as transmitters and receivers in the platform. To build a therapeutically effective MIS, it is critical to clearly understand the characteristics of the microwave antenna. The antenna used for transmitting and receiving should be planar, wideband, compact, directional, and have a high radiation efficiency in order to producean effective MIS with high resolution and dynamic range. The wideband features allow for great resolution and precise target localization while imaging. Furthermore, information spanning a wide frequency spectrum can be acquired in a single test, allowing for fast data collecting and microwave detection. Very short microwave energy pulses are required in a near field wideband detection, which is an important requirement for medicinal applications involving electromagnetic fields [15]. In this case, the planar log periodic antenna is a suitable candidate for MIS as it has high gain, low profile, wide bandwidth, and high directional patterns [16]. There are a number of simulations and experimental results that have been shown to detect breast tumors using MIS [17, 18, 19, 20, 21, 22, 23, 24, 25]. In [17], an experimental near-field MIS prototype at Dartmouth College was described. It used sixteen transceiving monopole elements between 300 and 1000 MHz. A tank between the antennas and the breast served as a coupling medium. The array of antennas was moved vertically and tuned using the mechanical switches. In [18], a monostatic radar-based MIS was developed to scan patients in the clinical trial. The system consisted of antipodal Vivaldi antenna as a sensor, laser, and cylindrical container with canola oil as a coupling medium to reduce skin reflections. The Delay and Sum algorithm (DAS) produced consistent results in the wideband range but was limited to only eight patients. In [19], a multistatic 16-antenna hemi-spherical array operating in the 2-4 GHz frequency range was used in the time-domain radar system. The results of an investigation into measurement repeatability and its impact on image reconstruction were presented. The measurement repeatability was high due to careful patient positioning in the system and in relation to the immersion medium. The measurement setup consisted of reflectors, pulse generators, couplers, and amplifier. In [20], an UWB-based near-field MIS using a raster scan algorithm was presented. The researchers presented the measured and simulated results using a homogenous and a heterogeneous 3D breast phantom.