Existing screening techniques for detecting breast cancer like X-ray Mammography, Magnetic Resonance Imaging (MRI), and Computer Assisted Tomography (CT) have some drawbacks, such as the inability to detect cancer at early stage, over sensitivity or requirement of breast compression. A new approach that has the potential to overcome these shortcomings is Ultra Wide Band (UWB) microwave imaging. This imaging method is based on solving Maxwell’s equation to determine dielectric properties profile with known electric field measured by antennas surrounding the breast. As small planar UWB antennas suitable for microwave imaging are not commercially available, our goal is to design and fabricate UWB antenna system for microwave imaging to detect breast cancer. As time domain behaviors of antenna are essential for imaging, Finite Difference Time Domain (FDTD) technique will be used for design and study of the performance of the antenna system.