An antenna for a Radio-Frequency IDentification (RFID) system is disclosed that comprises a pair of resonant cavities. The antenna is realized by folding the ends of a ribbon of conductive material, such as metal foil, over the middle part of the ribbon. The antenna generates a higher voltage than prior-art antennas used in RFID systems, and it makes possible RFID systems with an improved range. In an alternative embodiment, the antenna comprises a reflector that enables the RFID system to better tolerate the presence of nearby metal objects.