A virtual thermometer with low measuring hysteresis for high performance MEMS resonant sensors

This paper proposes a novel method to acquire MEMS resonator's temperature based on the measurement of quality factor via continuous ring-down without additional thermometer. Quality factor, a parameter of resonator is utilized as a virtual thermometer, which attenuates measuring hysteresis and improves the performance of temperature compensation. In addition, to precisely measure the quality factor, continuous ring-down technique is employed, in which quality factor is frequency modulated to increase the robustness against the temperature effect in circuit blocks. As a result, this virtual thermometer is suitable and promising to be employed in high-accuracy MEMS resonant sensors. A prototype based on FPGA has been implemented. Experiments show that quality factor has a better correlation with frequency compared with the temperature measured outside. The precision of this virtual thermometer is 0.3Ό and the repeatability is 220 ppm. The temperature stability of the resonator is reduced to 279ppm with simple linear compensation by quality factor, which is 7X better than that based on external thermometer.