A Digital ClosedLoop Sense MEMS Disk Resonator Gyroscope Circuit Design Based on Integrated Analog Frontend A digital closedloop system design of a microelectromechanical systems (MEMS) disk resonator gyroscope (DRG) is proposed in this paper. Vibration models with nonideal factors are provided based on the structure characteristics and operation mode of the sensing element. The DRG operates in force balance mode with four control loops. A closed selfexcited loop realizes stable vibration amplitude on the basis of peak detection technology and phase control loop. Forcetorebalance technology is employed for the closed sense loop. A highfrequency carrier loaded on an anchor weakens the effect of parasitic capacitances coupling. The signal detected by the charge amplifier is demodulated and converted into a digital output for subsequent processing. Considering compatibility with digital circuits and output precision demands, a low passband sigmadelta (xcexa3xcex94) analogtodigital converter (ADC) is implemented with a 111.8dB signaltonoise ratio (SNR). The analog frontend and digital closed selfexcited loop is manufactured with a standard 0.35 xc2xb5m complementary metaloxidesemiconductor (CMOS) technology. The experimental results show a bias instability of 2.1 xc2xb0h and a nonlinearity of 0.035% over the xc2xb1 400xc2xb0 fullscale range.

Harmonic Distortion Optimization for SigmaDelta Modulators Interface Circuit of TMR Sensors The tunneling magnetoresistance microsensors (TMR) developed by magnetic multilayer material has many advantages, such as high sensitivity, high frequency response, and good reliability. It is widely used in military and civil fields. This work presents a highperformance interface circuit for TMR sensors. Because of the nonlinearity of signal conversion between sensitive structure and interface circuit in feedback loop and forward path, large harmonic distortion occurs in output signal spectrum, which greatly leads to the reduction of SNDR (signal noise distortion rate). In this paper, we analyzed the main source of harmonic distortion in closedloop detection circuit and establish an accurate harmonic distortion model in TMR microsensors system. Some factors are considered, including nonlinear gain of operational amplifier unit, effective gain bandwidth, conversion speed, nonlinearity of analog transmission gate, and nonlinearity of polycrystalline capacitance in highorder sigmadelta system. We optimized the CMOS switch and firststage integrator in the switchedcapacitor circuit. The harmonic distortion parameter is optimally designed in the TMR sensors system, aiming at the mismatch of misalignment of frontend system, nonlinearity of quantizer, nonlinearity of capacitor, and nonlinearity of analog switch. The digital output is attained by the interface circuit based on a lownoise frontend interface circuit and a thirdorder sigmadelta modulator. The digital interface circuit is implemented by 0.35xcexbcm CMOS (complementary metal oxide semiconductor) technology. The highperformance digital TMR sensors system is implemented by double chip integration and the active interface circuit area is about 3.2 xc3x97 2 mm. The TMR sensors system consumes 20 mW at a single 5 V supply voltage. The TMR sensors system can achieve a linearity of 0.3% at full scale range (xc2xb1105 nT) and a resolution of 0.25 nTHz12(1Hz).