Biography
Enrollment Date: 2008
Graduation Date：2011
Degree：M.S.
Defense Date：2011.05.24
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design of Passive UHF RFID Tag Circuits and On-chip Antenna
Abstract:
The main research emphases of passive UHF tag is focusing on improving the tag sensitivity and reducing tag fabrication cost. Designing a voltage multiplier rectifier with high power conversion efficiency and low turn-on voltage is an effective approach to improve tag sensitivity. This paper presents two AC-DC voltage multiplier rectifiers: a cross-connected CMOS rectifier circuit and a Dickson voltage multiplier based on Schottky diodes. In order to reduce the power consumption of the tag in low communication rate based on ISO/IEC 18000 Type 6C, we design a dual clock generation circuit. The coding and decode clock can be chosen according to the communication rates. RFID tags with on-chip antennas (OCA) not only save antenna fabrication and packaging costs but also reduce the tag size to adapt to the harsh size requirements. This article discusses the method of integrating RFID tag antennas in CMOS process. Two on-chip antennas used in different applying situation is presented. A near-field loop reader antenna magically coupled to the integrated tag antenna is utilized to conduct power and data transfer. The two magnetic coupled RFID systems have a communication distance of 4mm and 1.3cm respectively when the reader generating an output power of 20dbm. Finally, this paper describes a new kind of tag antenna package method. We integrated a feed ring in tag chip and designed an off-chip meandered shape antenna, magnetically coupled to the integrated feed ring. The power received from the off-chip radiator can magically deliver to the feed ring, then to the tag circuits. As there is no physical contact between the chip die and the off-chip antenna, this structure can be used as an economical and convenient method for RFID tag packaging. Test results show that with a 6dBi reader antenna, the proposed tag with this contactless packaging method can operate at a distance of 5m when the reader transmits 1W RF power.