Wei Ping Chen

A High Bandwidth Sigma-Delta Modulator Applied in Micro-Gyroscope

In this paper a fourth-order single-loop sigma-delta modulator applied in micro-gyroscope is designed. The modulator system chose the fully feedforword structure. The signal bandwidth is 200KHz, oversampling ratio is 64 and sampling frequency is 25.6MHz. By system simulation result in Matlab, the signal to noise ratio (SNR) is 92.3dB and effective number of bits (ENOB) is 15.03bits. The whole circuit of modulator is designed and simulated in Cadence Spectre. It is gotten that the SNR is 78.6dB and changes linearly with input level. When input level is bigger than -4dBFs, the modulator becomes overload.

Design of a Digital Decimation Filter for High-Precision 4-Order Sigma-Delta ADC

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.

Structure Design of a Novel Micromachinined Tuning Fork Gyroscope with High Robustness

A novel silicon based dual-mass vibrating tuning fork vibratory gyroscope (TFG) with differential capacitor structure is designed in this paper. the U-shaped beam is adapted to connecting the two decoupling movement of the framework structure in order to achieve the independent of the movement of drive direction and sense direction. The TFG structure is also optimized to further reduce the mechanical coupling of the device. The drive combs are designed on the mass, while the sense combs are designed on the frame. All the combs in this gyroscope are dominated by slide-film air damping in order to lower the air damping. This gyroscope is designed to obtain robust operation against variations under atmospheric pressure condition. The TFG is tested at atmospheric pressure with a sensitivity of 17.8mV/◦/s and a linearity of 99.989%, capacitance structure sensitivity is 21.5αf/◦/s with an equivalent noise angular rate of 0.028◦/s/Hz1/2, respective.

Stability Analysis in High-Order Electromechanical Sigma-Delta Accelerometer

A nonlinearity model including distortion components for sigma-delta (ΣΔ) accelerometer that allows stability analysis is described. Based on this model, closed-loop stability and signal dependent stability are analyzed detailedly. To verify the conclusions, Matlab/Simulink model for a fourth-order ΣΔ accelerometer is designed. The simulation results indicate that high-order system needs a large compensation coefficient, and it will not affect the performance due to the very high low-frequency gain of the loop filter. High-order system is conditionally stable, and stability is affected by the input signal.

Functional Study of Fluxgate Sensors with Amorphous Wires Cores

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 sensors 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.

Analysis of Tunneling Piezoresistive Effect of P-Type Polysilicon Nanofilms

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.

Damping Analysis of Asymmetrical Comb Accelerometer

The resonance phenomenon is suppressed by adjusting the damping of the comb accelerometer structure to widen the frequency bandwidth of the capacitive accelerometer. The capacitive accelerometer with asymmetrical combs, fabricated with DRIE and anodic bonding, is presented. The damping category of the accelerometer is introduced, in which the squeeze-film damping coefficient and the damping ratio factor are detailed. The damping ratio factor of the accelerometer, measured by a vibration method, is 0.17. The damping ratio factor of the optimized structure is calculated of 0.15 to 0.18 with the change of experiential modulus C from 25 to 30, theoretically.

A New Method of Design and Verification of Digital Silicon Gyroscopes Closed-Loop Driving System Based on MicroBlaze

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.

A 16 Bits Sigma-Delta Modulator Applied in Gyroscope

In this paper, a 4th-order sigma-delta modulator applied in gyroscope is presented. This modulator adopts the 2-1-1 Multi stage noise shaping structure. The bandwidth of signal is 100 KHz, the over sample rate is 64, and sample frequency is 12.8MHz. By the MATLAB Simulink modeling and simulation, when the input signal is 100 KHz, the SNDR of the MASH ADC is 121.8dB, and the effective number of bit is 19.93 in ideal situation. After considering non-ideal factors, the SNDR is 111.6dB, the effective number of bit of ADC is 18.28. Compared with the ideal situation, the noise floor of PSD has increased 40dB. It explains that non-ideal factors have a significant effect on the performance of the sigma-delta ADC. The 4th-order MASH sigma-delta modulator has been implemented under 0.5 um CMOS process and simulated under Cadence. The final simulation results show that SNDR is 112.4 dB and effective number of bits (ENOB) is 18.6.

A Low Noise Operational Amplifier Design Using Chopper Stability

Noise has become a significant bottleneck limiting the performance of the op amp, and chopper stabilization technology [1] is commonly used to reduce the noise of the op amp. The chopper stabilization technology can significantly reduce the low-frequency 1/f noise of op amp, then reducing the total low-frequency noise of op amp. In this paper, we designed a chopper-stabilized low-noise op amp, and used Cadence software for simulation and debugging.