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Now showing items 1 - 16 of 173

  • A method to reduce harmonic distortion of MEMS accelerometer

    Wang, Hang   Yin, Liang   Chen, Dong Liang   Li, Ling   Liu, Xiao Wei  

    This paper recommends a method to reduce harmonic distortion of MEMS accelerometer. The fifth-order MEMS accelerometer interface circuit designed in this work used the Cascade-of-Integrators, Feedforward modulation structure. This paper analyzes and calculates the main sources of HD, the unstable problem brought by the vacuum encapsulation sensitive structure. The use of front-phase compensation and the increase in loop forward gain helps ensure the system's stability as well as reduce the system harmonic distortion. Simulink is used to get the simulation results. After harmonic optimization, the third harmonic reached -141.83 dB, the Signal-to-Noise-and-Distortion-Ratio rose to 118.1 dB, the noise density is under 200 ng/Hz(1/2), the effective number of bits rose up to 19.33 bits.
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  • A Low Noise Operational Amplifier Design Using Chopper Stability

    Liu, Xiao Wei   Liu, Liang   Yang, Jian   Chen, Song   Chen, Wei Ping  

    Noise has become a significant bottleneck limiting the performance of the op amp, and chopper stabilization technology 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.
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  • The Design of the Integrator of Sigma-Delta Modulator

    Liu, Xiao Wei   Chen, Song   Liu, Liang   Yang, Jian   Chen, Wei Ping  

    A kind of fully differential integrator is designed for the modulator of Sigma-delta ADC in this paper. Fully differential structure is adopted to enlarge the amplitude of output, restrain nonlinearity and increase competence of anti-interference. The frequency of signal in this design is 10kHz and the frequency of clock signal is 100kHz. The design of fully differential integrator, capacitive common mode feedback, two-phase unoverlapping clock and switched capacitor integrator are accomplished in this paper. The simulation results in Cadence using 0.5um process show that the low-frequency gain of operational amplifier is 69.87dB, unity gain bandwidth is 37.74MHz, phase margin is 67.73 degrees and slew rate is more than 31V/mus.
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  • A Fourth-Order MASH Sigma-Delta Modulator in Inertial Sensors

    Liu, Xiao Wei   Li, Qiang   Sun, Guan Nan   Liu, Wen Yan  

    The theory of a Sigma-Delta modulator is introduced in this paper. Based on this theory, a feedback 2-1-1 multi-stage-noise-shaping (MASH) sigma-delta modulator is designed, and the coefficients of the modulator are calculated. The system-level simulation results show that the effective number of bits (ENOB) is 24 bits when the signal bandwidth is 1 kHz and the over-sampling (OSR) rate is 128. Then the circuits of modulator are designed, including integrator, comparator, multi-phase clock and the noise cancelling logic. The whole modulator is simulated in Cadence, the signal to noise ratio (SNR) of the modulator is 125.4dB, and the ENOB is 21.1bits, which meet the technical requirements of the sensor.
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  • A Microfluidic Chip Microwave Bonding Method Based on the PMMA

    Liu, Xiao Wei   Han, Xiao Wei   Zhang, He   Jiang, Xi Yun   Zhao, Lin  

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  • Synthesis of High Density Boron Nitride Nanotube Film

    Liu, Xiao Wei   Li, Ling   Dai, Ja Ne   Li, Lu Hua   Chen, Ying  

    Antiwetting BNNT films have been achieved by milling-ink method. Superhydrophobic (CA <5deg) are demonstrated on films with stainless steel as substrate. The high density and purity are confirmed by EDX and NEXAFS. There are only a few oxygen point defects in the form of nitrogen vacancies due to ink and annealing process in air.
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  • Nonlinearity Analysis of Closed-Loop ΣΔ Micro-Mechanical Accelerometer

    Liu, Xiao Wei   Xu, Hong Lin   Lv, Bing Jun   Zhou, Jia Jun   Chen, Song   Yang, Jian  

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  • Design of CTS Measurement & Control System Based on the VXI Bus

    Liu, Xiao Wei   Ma, Yu   Qin, Yong Ming  

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  • A bandpass sigma-delta modulator with the function of adjustable center-frequency

    Di, Xin Peng   Chen, Wei Ping   Liu, Xiao Wei   Fan, Ling Yun  

    A bandpass sigma-delta modulator with the function of adjustable center-frequency is present in this paper. A method used to convert 2-order low-pass modulator to 4-order bandpass modulator is proposed to realize the design. Center-frequency that can be set to 1/6, 1/4 and 1/3 of sampling frequency is controlled according to the digital logic voltage. The bandwidth of pass-band is 200 Hz. Test results show that the average SNR is about 80 dB at different center-frequency when the sampling frequency is 64 kHz. The input signal can reach to -3 dBFs. The complexity to design a variable center-frequency bandpass modulator is greatly reduced.
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  • Investigation on Silicon-Glass Electrostatic Bonding Time Experiment

    Liu, Xiao Wei   Tang, Jia Lu   Chuai, Rong Yan   Zhang, Hai Feng   Wang, Xi Lian  

    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℃ to 370℃; the best temperature for this bonding is about 350℃; however, when the temperature is below 280℃,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℃,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.
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  • System Design of Nonideal Fourth-Order Sigma-Delta Micromachined Accelerometer

    Liu, Xiao Wei   Li, Zhi   Sun, Guan Nan   Liu, Yun Tao  

    The paper describes the system design for a nonideal capacitive micromichined accelerometer in MATLAB/SIMULINK. In this paper, a fourth-order sigma-delta micromachined accelerometer system design is represented, which includes the electrode movement and circuit noise. By simulation and comparison with the ideal 4th-order sigma-delta accelerometer in MATLAB, we have found that the SNR is essentially influenced by the electrode movement. Moreover the influence of the electrode stiffness Ke is researched. We have also researched the effects of the kT/C noise and the front-end amplifier noise. This nonideal accelerometer system can represent more accurate simulation result.
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  • Fabrication and Testing of SOG Structure Flat Heat Pipes with Triangle Grooves

    Liu, Xiao Wei   Wang, Chao   Han, Tian   Dong, Tian  

    A new kind of charging and sealing method for SOG (silicon on glass) structure micro heat pipe with triangular grooves is investigated. MHP (micro heat pipe) is fully charged in a vacuum atmosphere which is useful for preventing air intermingle. Experimental results shows that when the fill ration of working fluid is about 35%, thermal conductivity of MHP with ethanol as its working fluid has an improvement of 19% compared to empty MHP.
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  • Gauge Factor and Nonlinearity of P-Type Polysilicon Nanofilms

    Liu, Xiao Wei   Lu, Xue Bin   Chuai, Rong Yan   Shi, Chang Zhi   Huo, Ming Xue   Chen, Wei Ping  

    The gauge factor and nonlinearity of 80 nm polysilicon nanofilms with different doping concentration were tested. The experimental results show that, from 8.1times10 18 cm -3 to 2.0times10 20 cm -3, the gauge factors first increase then decrease, which like the common polysilicon films (thickness is larger than 100 nm). From 2.0times10 20 cm -3 to 7.1times10 20 cm -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 4.1times10 19 cm -3, the nonlinearities are big, and the nonlinearities become small when doping concentration is high than 4.1times10 19 cm -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 times 10 19 cm -3 . The conclusions are very useful for design and fabrication of polysilicon nanofilms piezoresistive sensor.
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  • Experimental Research of the Anodic Bonding in the Si-Glass-Si 3-Layer Structure

    Liu, Xiao Wei   Tang, Jia Lu   Chuai, Rong Yan   Zhang, He  

    3-layer anodic bonding is one of the key technologies in the manufacture of complicated structure. The microcosmic process and current model of the 3-layer anodic bonding was investigated, and a new technology scheme with better bonding effect was developed. Using the experiment device, quantities of bonding current curves were obtained by the data collecting system. Under tensile testing device, intensity of the bonding was tested. By analysis of the data collected, the 3-layer bonding model was inspected, and the efficacy of the new technology scheme was proved.
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  • Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

    Wang, Yang   Liu, Xiao Wei   Zhang, Hai Feng   Zhou, Zhi Ping  

    We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H2O, and then in boiling water) and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene) and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161 degrees and a sliding angle of 3 degrees. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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  • Research on Combined Environmental Stress Test for Hybrid Integrated DC/DC Converter

    Liu, Xiao Wei   Ji, En Rong   Xu, Xiao Hua  

    The combined environmental stress test for hybrid integrated DC/DC converter is studied in this paper. Also several stress factors and combined environmental stress test profile are analyzed. In further, the failure modes of environmental stresses are discussed.
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