13.56 MHz-RFID biosensor with on-chip spiral inductor

The radio frequency identification (RFID) technology has become very popular in many fields; anti-theft devices, smart card and library management. Recently, RFID biosensor chips have been reported, which integrates RFID and biosensor for inexpensive, small and subaqueous sensing system [1]. However, RFID system typically uses external off-chip antennas, so that additional fabrication time and cost are required for the post process. This paper investigates the RFID biosensor with on-chip spiral inductor as the tag antenna. First of all, we assume the operating frequency 13.56 MHz that is suitable to subaqueous measuring system. Secondly, we simplify the process and reduce cost by integrating sensor chip and on-chip spiral inductor tag antenna that is fabricated with metal interconnect layer of standard complementary metal oxide semiconductor (CMOS) process. Finally, we propose the RFID biosensor circuitary (new modulation circuit and signal processing circuit), and the operation is confirmed by measurement. With such advances, low cost, low noise and simple measuring system can be expected.