A Passive UHF RFID Platform for Sensing Applications

In this work, a passive UHF RFID platform for sensing applications is presented. The platform consists of a passive UHF RFID tag and a base station. The tag has an inductively-fed, meandered dipole antenna that is impedance matched to a CMOS IC that contains the remote powering, power management, and communication circuits to operate with sensor interfaces. The power management includes an LDO voltage regulator, a bandgap voltage reference, and a current source. The rectifier is a three-stage, differential rectifier with threshold cancellation. The regulator is responsible for generating a stable supply voltage for sensor interfaces. The reference voltage of the voltage regulator is generated by the bandgap voltage reference. The supply independent current source generates a reference current to be used in the sensor interface circuit blocks. The tag chip has a backscattering modulator with a 1-bit data input to transmit the sensor interface output to the base station. A monostatic base station with a homodyne receiver is implemented using discrete components and a custom-made planar patch antenna. The operation of the whole system is shown by measurements. The tag chip is implemented in 0.18 mu m UMC CMOS process.