Microwave imaging techniques for biomedical applications has increased the interest of researches because its characteristics of non-invasive and low health risk. In this master thesis, a microwave brain circular tomographic imaging system is presented. Microwave tomography is an imaging technique that allows to recover the values of the complex permittivity of an inhomogeneous object based on the measurements of the scattered fields produced by a known incident field. The aim of this system is to detect the brain stroke which occurs due to a loss of blood supply into a part of the brain caused by a blood clot (ischemic stroke) or a bleeding (hemorrhagic stroke). To make this detection, the system designed in this work is based on an encircling geometry composed of 32 antennas equally spaced, divided in 4 sectors. When the system is working one sector act as a transmitter and the others acts as receivers. Each sector based on RF switches and microstrip lines that should have the same length to have the same losses and phase in each antenna. The system works at a frequency band between 300 MHz and 600 MHz. Finally, to make the initial test, a system with 2 sectors, one transmitter and one receiver, with 4 antennas each one is fabricated.