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Analysis And Design Of Semi-Passive UHF RFID Tag Chip

Posted on:2011-03-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:W Y CheFull Text:PDF
GTID:1118360305997236Subject:Microelectronics and Solid State Electronics
Abstract/Summary:PDF Full Text Request
RFID (Radio Frequency Identification) is a technology that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency portion of the electromagnetic spectrum to uniquely identify an object. Semi-passive tag uses the internal battery to supply its signal processing and data storage circuits, and communicate with readers by employing passive tag's backscatter mechanism. Thanks to the battery, problems caused by power source in passive tag are solved. Therefore, semi-passive tag is hopefully capable of having better performances in read range and read range. Besides, advanced functions like sensor employment and security protocols become realizable. These qualities make semi-passive tag highly expected in applications like post management, dangerous cargo surveillance and cold chain logistics.By studying the physical mechanism and signal transmission of a UHF (Ultra High Frequency) RFID system, semi-passive tag's improvement in read range and read rate is theoretically verified. The mathematical method for calculating the read range of a backscattered UHF tag is evolved by employing readers' energy requirement for correct signal detection. According to different reader and tag performances, read range's limitation factors are given. Afterward, this work uses an indoor UHF propagation channel to study the read range's dependence on probability. Semi-passive tag's improvement in read rate is evaluated quantitatively, and the concept of safe read range is proposed consequently.Subsequently, design and optimization methods for semi-passive tag chip are discussed. For the purpose of prolonging tag's life cycle and employing new on-chip functions, key techniques in designing a semi-passive tag chip are studied. These techniques are realizing high communication sensitivity and wireless charge function by one rectifier, stable wake-up control with almost zero power consumption, and on-chip truly random number generation.With the aforementioned analysis and the proposed key techniques, a semi-passive UHF tag chip with temperature sensor is designed and implemented in SMIC 0.18μm EEPROM CMOS technology. Sensor application problems, such as the coexistence of real time temperature sensing with temperature log, and wake-up conflicts, are solved. Quasi-constant current-constant voltage wireless charge and overcharge protection function is realized in the chip. Measured sensitivity and sleep current is-23.7 dBm and 150 nA respectively.
Keywords/Search Tags:Ultra High Frequency (UHF), Radio Frequency Identification (RFID), Semi-Passive Tag, Read Range, Read Rate, Thin-Film Battery, Wireless Charge, Wake-Up Circuit, Truly Random Number Generator (TRNG), Temperature Sensor
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