Near-field power transfer and backscattering communication to miniature RFID tag in 65 nm CMOS technology

This work introduces an inductive wireless power transfer (IWPT) and backscattering communication to an extremely small CMOS RFID tag with a size of 200 μm by 200 μm. This is the smallest RFID tag to date, with the passive area taken into account. DC power of 0.1 mW can be generated on-chip with 21 dBm source power at 2 GHz. An amplitude-shift keying (ASK) back-scattering communication link is demonstrated. The on-chip matching varactor is switched to maximize the distance between the two reflection (backscattering) coefficients. A directional coupler is used to suppress the Tx-to-Rx leakage and to extract the backward scattering wave. An 8-bit, 5-GS/s ADC can demodulate the 625kb/s backscattering signal.