The use of antenna arrays at emission and reception seems to represent a prominent solution for future wireless systems, it improves data rates and enhances the quality of service. The performance of these systems depends mainly on the propagation channel. Therefore, channel's characterization and modeling are crucial. In this document, we present a MIMO (Multiple Input Multiple Output) channel sounder at 3.5 GHz developed at IETR. One of the applications operating at this frequency is the WiMAX system. Different antenna arrays architectures are designed and calibrated at 3.5 GHz for high resolution MIMO channel sounding. Antenna arrays beam patterns are measured and calibrated. The importance of this work is shown by ESPRIT simulations. Propagation measurement results are needed to obtain realistic MIMO channel models.