An antenna system that allows increasing the reading reliability of RFId systems by dynamically changing the shape or the polarization of the electromagnetic field radiated by the RPId reader. The system includes at least one reconfigurable antenna, a variable DC bias unit and a methodology to efficiently use the system in RFId applications. The system allows changing the direction in which the energy is radiated or the polarization of the radiated field in order to “move” the electromagnetic field and to also read RFid tags that receive faint signals with standard RFid systems. Polarization alignment between the reader's antenna and the transponder allows for maximum power transfer, while changing the direction of radiation allows concentrating the electromagnetic field towards the transponder.