Full passive RFID pressure sensor with a low power and low voltage time to digital interface

Abstract

There is a strong motivation for the development of low-power RFID sensors tags. In this work, a full passive RFID pressure sensor tag is presented paying special attention to a time to digital converter based on nonius oscillators. The circuit has been designed using a 90nm CMOS standard process. Post-layout simulations show that the nonius converter allows the estimation of the input pulse width in the range from 34μs to 51μs with a LSB of 2ns and an effective resolution of 8.3 bits. It requires a maximum conversion time of 97.8μs with an average power consumption of 1.59μW from a 0.7V supply voltage. The comparison of these results with the state of the art showed that, according to the authors' knowledge, the proposed sensor interface has the best characteristics in terms of minimum power consumption and supply voltage level. Therefore, it is a remarkable solution for passive RFID sensor applications.