An improved antenna structure for RFID tags uses a pair of bent dipole antennas having arms that extend substantially about an outer edge of an RFID substrate. The antennas can be adjusted to resonance at about a half-wavelength of an applied electromagnetic field in the conductive material of the antennas. The antennas can be shorted together using a shorting path, the position of which can be adjusted to adjust an input impedance of the antenna structure. A shorting stub can be used to couple the antenna structure to a supply voltage connection of an RFID device used for the tag. The overall length of the shorting stub can be adjusted to match the impedance of the antenna structure to the impedance of the RFID device. These antenna structures can be used with RFID devices such as CDIP devices and bumped die packages.