Low-power oscillator for passive radio frequency identification transponders

Passive radio frequency identification tags extract energy from incoming electromagnetic waves to power up their internal circuitry. Such a limited source of power demands efficient circuits to minimise the power consumption. In this work a new technique is proposed to design a low-power ring oscillator in which the voltage swing of internal nodes are constrained to lower the dynamic power consumption. The proposed power reduction technique can be employed for RFID tags operating over different frequency bands from low frequency (LF) to microwave. A low-power oscillator operating in the medium-frequency range (6-16-MHz) for applications such as electronic article surveillance and item management has been implemented in this work. Post-layout simulation results using STMicroelectronics CMOS 65-nm technology indicate that the proposed method can reduce the power consumption by more than 25%.