Papers by Author: Xiao Wei Liu

Abstract: A high-order interface circuit based on sigma-delta (ΣΔ) modulation is advantageous to enhance the resolution and reduce the quantization noise of micro-accelerometer, while the performance is restricted by the effect of nonlinearity of op-amp, electrostatic force feedback and quantizer. A fifth-order closed-loop ΣΔ capacitive accelerometer is proposed in this paper and a theoretic nonlinearity of the accelerometer was investigated. The nonlinear behavioral models based on SIMULINK are given in the paper. The simulation and test result are presented through optimization based on the nonlinearity analysis at last.

Abstract: In this paper, we make a detail analysis of some factors, which affects the electrostatic bonding process. According to the electrical properties of glass, combined with the principle of electrostatic bonding, we analysed the relationship of critical bonding time, voltage and temperature as well as the factors which affect electrostatic bonding. Then we come up with the mathematical model of the intensity and temperature of electrostatic bonding. In accordance with the above-mentioned formula and the experimental data, we can get the following conclusions: the intensity of electrostatic bonding is much greater between 280°C to 370°C; the best temperature for this bonding is about 350°C; however, when the temperature is below 280°C,the intensity of electrostatic bonding is lower due to the great impact of particles under low temperature; but when the temperature is higher than 370°C,the mismatch of coefficient of thermal expansion of silicon and glass gets larger, then as a result, the intensity of this bonding has a significant decrease with the increasing of temperature.

Abstract: In this work, closed-loop self-oscillating driving circuits for gyroscopes based on DC PI controller are analyzed in theory. The condition for oscillation is achieved by solving electrical differential equation, and the effects of key factors on magnitude stability are discussed. Further, an ASIC based on PI controller is designed, which is verified by simulation. The test results of manufactured chip correspond with the theoretical analysis, showing that this ASIC is capable of driving low-Q gyroscopes at normal temperate and pressure. This theory for analysis and the designed chip contribute to guide the design of closed-loop driving for gyroscopes, also improving stability for oscillating circuits.

Abstract: In this paper, the writers reported on a fluxgate sensor and a CMOS-ASIC for sensor supply. The design method and principle of the interface circuit of the fluxgate sensor was also presented, which was based on second-harmonic detection of the output voltage. This circuit has been simulated and realized through 0.5μm DPDM P-sub CMOS Process. The size of this circuit is 2mm×2mm. The circuit exhibited a sensitivity of 16.5mV/μT and a linear range of ±90μT. With 5V of voltage supply, the total power consumption of the circuit was as low as 35 mW.

Abstract: The amorphous material Co-based wires as the sensing element in Vacquier type sensor was studied. The magnetic material used in these sensors is CoFeSiB wires produced at the harbin Institute of Technical Physics and prepared by melt extraction. The sensor's functional parameters were measured. The sensor sensitivity is 3.1mV/μT. The measurements demonstrate the usability of the sensor in a magnetometer for both continuous and alternating magnetic field measurements.