Abstarct: This dissertation investigates and simulates a microwave imaging system for breast cancer detection in the frequency range of 3 to 15 GHZ and uses a confocal radar algorithm or delay and summation type (DAS).in the first step of this research, we examined the different antennas used in microwave imaging systems and with the studies performed, we reached a final conclusion about the requirements of a suitable antenna for use in this system.for this purpose, we selected and designed a logarithmic spiral antenna with circular polarization and back cavity that has good performance in terms of frequency and time. the design of this antenna due to the wide bandwidth and the presence of the back cavity and the use of balun to feed the antenna has faced challenges that have been overcome by using absorbers in the mextal enclosure and proper design of the antenna and balun structure. the designed logarithmic spiral antenna has a wide axial ratio bandwidth and impedance bandwidth, and the antenna radiation pattern is stable in the frequency range of 3 to 15 GHz and has little distortion in the time domain.in the next step is to use the DAS imaging algorithm with the investigations and simulate the structure as a monostatic with plane placement. to start, we used a dielectric sphere in open space. by keeping the position of the antenna to be scanned on the X and Y screens, it changed the location of the tumor at five different points, and the resulting images were successful. then a phantom in the form of a rectangular cube and a spherical tumor in accordance with the specifications given in different references has been designed to evaluate the performance of the antenna and the implemented algorithm has been used.the performance of the proposed method has been evaluated by moving the spherical tumor in different places, especially near the edges. studies show that when the dielectric characteristics of the phantom and the tumor are selected with near realistic characteristics, even with a single phantom scan, the images reveal the location of the tumor with high accuracy. the obtained images have a highr signal-to-clutter ratio compared to similar articles on the diagnosis of breast cancer by microwave imaging.