Antennas for UHF-RFID printer-encoders

The design criteria for near-field antennas of UHF-RFID printer-encoders are here addressed. The encoder antenna has to communicate with the targeted UHF-RFID transponder from among a group of multiple adjacent transponders. The encoder and transponder antennas are very close to each other (a few mm apart), and the size of the encoder antenna is strictly determined by the printer-encoder composite architecture. The most important performance parameters are the level and the spatial selectivity of the power delivered to the transponder chip. Preliminary numerical results are shown for a set of reader antennas, while COTS devices are considered for the transponder model.