Automatic Antenna Tuning Unit to Improve RFID System Performance

作者：Wegleiter Hannes^*; Schweighofer Bernhard; Deinhammer Christian; Holler Gert; Fulmek Paul

来源：IEEE Transactions on Instrumentation and Measurement, 2011, 60(8): 2797-2803.

DOI：10.1109/TIM.2011.2122390

• Antenna accessories
• impedance matching
• loop antennas
• magnetic devices
• magnetic-variable control

Systems for radio-frequency identification (RFID) realize a bidirectional wireless communication between a reader device and cheap passive tags (e. g., an RFID chip with an antenna printed on badges for access-control systems) in the near field of an antenna. This paper deals with the automatic and fast tuning of the resonant reader antennas in the widely used 13.56-MHz frequency band, resulting in a performance improvement and an increased READ/WRITE range. A novel RFID reader system is proposed with a tuning transformer for the automatic adjustment of the resonant circuit center frequency. This is achieved by shifting the magnetic operating point (i.e., the biasing direct-current (dc) magnetization) of a Ni-Zn ferrite transformer by means of an additional dc winding. The operation principle and the performance potential of this device are demonstrated by measurements on a prototypical RFID system.

• 出版日期2011-8