This thesis has been carried out in Grupo de Radiación of Señales, Departamento de Señales, Sistemas y Radiocomunicaciones from the ETSI de Telecomunicación of Universidad Politécnica de Madrid. The title of the thesis is "Planar Reconfigurable Antennas for Satellite Communications". It has been developed by José Manuel Inclán Alonso, Electrical Engineer Msc. under the supervision of Prof. Manuel Sierra Pérez.