Microwave imaging is being investigated by many research groups for its po- tential in medical diagnostic and treatment elds. Microwave signals are to sensitive to small changes into the dielectric properties of the objects under test which can be related to their physiological state. The use of UWB signals ( 3.1 - 10.6 GHz ) allow a good compromise between penetration and resolution. Moreover in the last years UWB frequency range has strongly exploited in med- ical imaging research eld, due to its characteristics of low-cost implementation and low-power used. The objective of this work is the design and the fabrication of multiplexed slot antenna array, that will be used in a 3D arrayed microwave tomographic system for medical imaging. This system is characterized by a rotation of mul- tiplexed linear antenna array around the object under test. With the aim of reducing the acquisition time it is replaced the vertical movement with a real antenna array. In the chapter 1 the introduction of medical imaging will be pre- sented and the system requirements are described. In the chapters 2 the basic concepts of UWB microstrip slot antennas and feeding methods will be analyzed respectively. In chapter 3 the individual array elements will be chosen and two array con gurations will be designed. In chapter 4 the feeding networks will be planned and simulated, the prototypes will be fabricated and the simulation data will be compared with measurement results. Finally the calibration will be done and the array con guration with the best performance will be chosen. In chapter 5 the conclusions will be deduced and the future works will be proposed.