Remote Frequency Calibration of Passive Wireless Microsensors and Transponders Using Injection-Locked Phase-Locked Loop

This paper proposes a new remote frequency calibration method that allows a passive wireless microsensor to adjust the oscillation frequency of its local oscillator using a calibrating reference signal sent by its reader. The reference signal is transmitted wirelessly by the reader in the form of a modulated tone. Frequency calibration is achieved by employing an injection-locking phase-locked loop that adjusts the oscillation frequency of the relaxation oscillator of the microsensor to that of the reference signal. The hysteresis of the relaxation oscillator is created by a novel mono-stable current pulse generating circuit also proposed in this paper. The proposed remote frequency calibration system has been designed in TSMC-0.18 mu m 1.8V 6-metal 1-poly CMOS technology and analyzed using SpectreRF from Cadence Design Systems with BSIM3V3 device models. The power consumption of the VCO is 525 nW while that of the system is 912 nW.