Energy Supply and ULP Detection Circuits for an RFID Localization System in 130 nm CMOS

This paper presents both an integrated energy supply and detection circuits for an RFID localization system. The equations to calculate the expected AC antenna voltage are presented as well as a fast method to calculate the expected output voltage from a rectifier. An ultra low power voltage detection circuit is described which monitors the output voltage of the rectifier and consumes only 3 nW. Also the input of the rectifier is monitored by an input power dip detection circuit, which provides a pulse whenever the amplitude of the AC antenna signal drops to zero. This circuit too, is ultra low power and consumes only 5 nW from a 0.5 V supply. It can even serve as an OOK demodulator for bitrates up to 6.7 kbps. All circuits have been designed in a 130 nm CMOS process. Measurement results are presented for all circuits.