Polarization and Frequency Agile RFID Reader Antenna via a Reconfigurable Feeding Network

This paper presents a patch antenna designed for Ultra High Frequency (UHF) Radio Frequency IDentification (RFID) reader achieving polarization and frequency agility by employing a reconfigurable feeding network inspired by stub theory. The switchable polarization improves the polarization efficiency in comparison with standard circular polarized antennas, while the frequency reconfigurability allows to use the same design to cover the European and US frequency bands. As further optimization, the patch antenna, has reduced size, for improving system integration. The combination of antenna and reconfigurable feeding network has been tested through simulations, showing a good matching over the two RFID frequency bands, while switching among four linear polarizations. The simulated results have shown a good polarization purity, however, the total efficiency is limited by the switching elements. Nevertheless, being a compact and low-cost solution, the proposed frequency and polarization reconfigurable feeding network is a good alternative to standard circular polarized designs.