The Design Of Passive UHF RFID Tag IC RF/Analog Front-end

With the development of "the Internet of things", radio frequency identification technology (RPED) has attracted great attention and got rapid development for its non-contact identification, small size, and large amount storage characteristics. With the application of new technologies, the research for UHF radio frequency identification (UHF RFID) tag chip has become one hot spot in the field of RFID.According to the specification of EPCTM C1G2protocol,we have introduced the physical basis and working principle of RFID system, and have studied on the RF/Analog front-end of UHF passive RFID tag chip and various circuit blocks, such as rectifier, LDO, power on reset circuit (POR), clock circuit, and ASK demodulator, etc.In the RF/Analog front-end, in order to improve the Power Conversion Efficiency (PCE) of rectifier, a novel diode connected MOS transistor is proposed. The proposed diode connected MOS transistor uses a new connection which leads to reduce the threshold voltage and leakage current in compare to conventional diode connected transistors. A five stages charge-pump rectifier is designed based on the proposed diode connected MOS transistor, and the PCE of rectifier is improved.For the regulator block of the RF/Analog front-end, we choose the Low Drop-out Linear Regulator (LDO). Traditional LDO need to attach a big capacitor and series resistance to maintain the stability of the circuit system, but capless LDO is good to reduce the area and the cost of the RFID Tag, so in this paper, we begin from the pole-zero analysis of capless LDO, then we have designed a stable capless LDO by adding a damping coefficient control module.According to low-power requirement of the passive UHF RFID tag ICs, the power dissipation is optimized in most circuit blocks in this paper.In this paper, all the circuit blocks are simulated on the standard0.18um CMOS process, the performance of each block can achieve the passive RFID application requirements.Some blocks are taped out and measured in the CSMC process.