Papers by Author: Wei Ping Chen

Abstract: In this paper, a 16 Bits 500 kHz Sigma-Delta DAC for Silicon Micro Gyroscope is proposedin order to enhance the precision of the digital to analog converter level.The interpolation filterhas achieved 64 times interpolation function,using three cascaded manner, it employs three level cascaded of FIR filterstructure. It achieves a 64 times oversampling feature. The signalbandwidth of the designs interpolation filter is 100 kHz, SNR reach 106dB. Fifth-order single-loop structure CIFB achieve noise shaping modulator function to verify the stability of the system, after the completion of CSD coefficient coding, signal to noise ratio reached 119.7dB, effective bits reached 19.59. The switched capacitor technology actualize analog reconstruction filter module, and using a typically switched capacitor DAC achieved high jump "0, 1" digital signal is converted into an analog signal, the digital-analog conversion achieved.

Abstract: The article brings out a digital silicon gyroscopes closed-loop driving system using the phase relationship of the input driving signal and the signal of the forced motion of the mass block in sensor structure based on analyzing the working principle and phase characters of digital silicon gyroscopes. We make a low-cost, simple and high precision measurement technique for resonant frequency of silicon micro-machinery gyroscopes by the whole digital locked loop system designed with MicroBlaze method. Dichotomy and Fourier transform spectrometry method constitute the algorithm of the system and the solution precision can be determined by the number of the times of approximation. Under the control of the MicroBlaze softcore, the system realizes the realization of the digital signal, the high speed frequency transformation, the acquisition of mass block response signal and the calculation of phase difference. Lastly, each module of the system and the whole system are simulated, the whole system is approved on the test broad.

Abstract: In this paper, a design of a digital decimation filter which has a output of 24 bits for high-precision 4-ordes Σ-Δ ADC is proposed. The digital decimation filter includes a CIC filter, a compensation filter and a half band filter. The over-sampling rate of the digital decimation filter is 256, the cutoff frequency is 1kHz, the coefficient of the pass-band ripple is -0.25dB, the stop-band attenuation is -162dB, simulation results using Matlab and modelsim are correct, the result of the FPGA verification shows that the design meet the requirement of the high-precision 4-ordes Σ-Δ ADC.

Abstract: Multi-wall Carbon Nanotubes (MWNTs) is the new hotspot material as the active sensing element, but there is no certain theory on the phenomenon of the vapor's capillary condensation in MWNTs for the present. This paper presents a new theory that the capillary condensation of vapor in MWNTs mostly occur in the internal hollow tube, according to the calculation of equivalent model of MWNTs. A kind of carbon nanotubes (CNTs) humidity sensor based on quartz crystal microbalance was fabricated, CNTs employed as adsorption materials. The sensor was put in 11% and 97% relative humidity environment in experimental, and the value of M_H2O/M_CNT was calculated. The theory in this paper is proved by the comparison between the experimental and the analysis results.

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.

Abstract: Quadrature error and Coriolis offset are main errors of micro-gyroscopes which caused by manufacturing imperfections. They deteriorate the overall performance of micro-gyroscopes. For inside sense outside drive frame micro-gyroscope, quadrature error and Coriolis offset have their own characters. Based on the mechanical analysis of inside sense outside drive frame micro-gyroscope in imperfect condition, the dynamic equations of condition with quadrature error and Coriolis offset are investigated, and an equivalent electrical model with quadrature error and Coriolis offset is presented. It is convenient to observe the effect of quadrature error and Coriolis offset by equivalent electrical model simulating. Three conditions are simulated and compared. The results indicate that the Coriolis offset reduces the amplitude of instantaneous displacement to a very small extent. Its effect can be neglected. Quadrature error causes an error displacement with the amplitude much bigger than the prefect displacement’s amplitude. It is the overwhelming error in ISOD frame micro-gyroscope.

Abstract: The gauge factor and nonlinearity of 80nm polysilicon nanofilms with different doping concentration were tested. The experimental results show that, from 8.1×1018cm-3 to 2.0×1020cm-3, the gauge factors first increase then decrease, which like the common polysilicon films (thickness is larger than 100nm). From 2.0×1020cm-3 to 7.1×1020cm-3, the gauge factors do not change with doping concentration almost, which can be explained by tunneling piezoresistive theory. When doping concentration is low than 4.1×1019cm-3, the nonlinearities are big, and the nonlinearities become small when doping concentration is high than 4.1×1019cm-3. The nonlinearity is related to the occupied condition of trapping states in grain boundary. The longitudinal gauge factor and nonlinearity are smaller than transverse ones. Take the gauge factor and nonlinearity both into consideration, the optimal doping concentration should be 4.1×1019cm-3. The conclusions are very useful for design and fabrication of polysilicon nanofilms piezoresistive sensor.

Abstract: The polysilicon nanofilms have significant piezoresistive characteristics. In this paper, an analysis of tunneling piezoresistive effect of p-type polysilicon nanofilms is presented based on the experimental data. The analysis results show that the tunneling piezoresistive effect is much remarkable than piezoresistive effect of neutral region, and the former is about 1.3 to 1.5 times of the latter. The higher is doping concentration, the more remarkable tunneling piezoresistive effect is. This advantage can be utilized to improve the temperature characteristics of polysilicon piezoresistive sensor.

Abstract: This paper researches on the temperature effects of a fully-symmetrical micromachined gyroscope. The Young’s modulus and thermal expansion coefficient of silicon vary with the environment temperature, which affects the modes’ resonant frequencies of micromachined gyroscopes. The effects of temperature fluctuation on the modes’ resonant frequencies is simulated by the FEM software ANSYS. The simulation results show that the fully-symmetrical gyroscope’s resonance frequencies decrease with the increase of temperature and the decrease degree nearly 0.256Hz/°C, but the two modes’ resonance frequencies matches well. The micromachined gyroscope’s dynamic characteristics are tested. The resonant frequencies and the quality factor are reduced with the increase of temperature and the decrease degree of the fit linear about the resonant frequencies is 0.276 Hz/°C. The test results are in good accordance with the simulation results.