Papers by Author: Yan Su

Abstract: In an electrowetting-based liquid microactuator, two types of insulating materials are used for device operation: an dielectric material to provide capacitance between the liquid and conductor, and a hydrophobic coating at the interface of liquid and insulator. This paper investigates important physical properties for the insulating materials. Several alternative dielectric materials are compared for application in EW chips, breakdown phenomenon of insulating layers with different thicknesses is tested before and after droplet actuation. It appears that the used EW devices have lower breakdown voltages than unused devices, probably due to the locally trapped charges in the insulating layer.

Abstract: The output-current of silicon microgyroscope is at the level of 10^-7A. So the requirements for circuits’ SNR are very high. This paper proposes a method to improve transimpedance amplifier interface circuit’s SNR. First of all, the operating principles of silicon microgyroscope and transimpedance amplifier interface circuit are introduced. Secondly, resistor thermal noise, amplifier’s current and voltage noise are analyzed. Then noise density in a certain frequency range is calculated based on Matlab. Besides, a method to improve SNR is proposed, namely, increasing the value of DC offset resistance. Finally, simulation based on Cadence is operated to verify the method. Simulation results fit well with the theoretical analysis. That means the method to improve the SNR is feasible.

Abstract: The output-current of silicon microgyroscope is at the level of 10^-7A, so the requirements for circuits’ SNR are very high. This paper conducts the simulation of closed-loop driving circuits in Cadence on the basis of a RLC series resonant circuit. It turns out that experimental results fit the simulation which has a great significance for improving the property of circuits. First of all, the operating principle of silicon microgyroscope is introduced. Secondly, a RLC series resonant circuit is established by measuring Q value and driving frequency. Then the overall simulation is conducted in Cadence combined with chips’ models offered by the manufacturers. Finally, the accuracy of simulation is verified by experiments. Experimental results show that, the relative error of driving sense signal’s value is 0.5%, for stability time the value is 0.6% and for driving frequency the value is 38ppm. Experimental results agree well with the simulation, which confirms simulation’s accuracy. This has a great significance for improving the property of circuits.

Abstract: The landslide process and mechanism of rainfall-induced landslides are assessed by using particle flow code in two dimension based on the discrete element method. The formation mechanism of rainfall-induced landslide is revealed by the analysis of displacement field, velocity field and stress of the slope versus time. The fluid velocity and porosity of sample increase gradually with the increase of water head, the violent fluctuation of contact number of movable particles show the violent motion of slope, then the slope maybe slide.

Abstract: There is a bias drift of silicon microgyroscope when power on which limits its application in higher precision field. This paper analyzes and validates the main cause of bias drift, combined with theoretical analysis of demodulation and experimental results, which has a great significance for improving the performance of silicon microgyroscope. First of all, operating principle of silicon microgyroscope is introduced and theoretical analysis on bias drift is made on the basis of DC output voltage of microgyroscope. Secondly, demodulated signals’ amplitude and phase are analyzed in Matlab with the experimental data. By contrasting theoretical and experimental bias drift, the accuracy of theoretical formula is verified. It turns out that, the relative error of bias drift from 2-hours value to stable value is 5.5%, it’s 6.6% for 1-hour value to stable value and for beginning it’s just 1.7%. Experimental results agrees well with the theoretical analysis, which verifies that the main cause of bias drift of silicon microgyroscope is the phase difference between Vds and Vsense. This conclusion can provide some guidance for structure design optimization and circuits improving.

Abstract: To improve the anti-vibration capability of silicon mcrogyroscope, making it works well under the vibration environment, this paper analyzes the dual-mass silicon mcrogyroscope and did the following works. First of all, the operating principle, analysis parameters of silicon microgyroscope and the vibration condition are introduced. Secondly, this paper proposes a vibration analysis method base on the signal conversion between time domain and frequency domain and establishes a Simulink demodulation model according to circuits of silicon microgyroscope. Finally, we get the conclusion that under the condition of vibration, composition with the same frequency of Vds in Vsense signal is the main influence factor of bias stability by analyzing experimental data. This has a great significance for improving the anti-vibration capability and guiding the interior structure design of silicon microgyroscope.

Abstract: Increasing the driving amplitude could improve the sensitivity of silicon microgyroscope, which is the effective way to enhance the performance of gyroscope. However the large driving amplitude leads to the nonlinear effect. As a result, the resonance frequency is dependent with the driving amplitude, which influences the frequency stability of gyroscope. The equivalent model of driving beam is established, and the stiffness formulas of driving beam are derivated according to the large deflection theory. The linear stiffness of driving beam is 270.1N/m and the nonlinear stiffness is 3.237×108N/m³, which are 2.7% and 6.4% different from the simulative results. Harmonic balance method can be used to establish the relationship between driving amplitude and resonance frequency. The theoretical analysis results are carried out compared with the simulative analysis results. Also the impact of driving amplitude on resonance frequency is confirmed by experiment test. This paper is significant for improving the frequency stability, and provides a theoretical basis for optimizing the structure of gyroscope.

Abstract: Infrared biosensor has been a hot area of research for several years in infrared field. This paper proposes a method to test infrared biosensor array which is not bonding with ROIC. The presented ROIC-less infrared biosensor is encapsulated in a vacuum chip scale packaging, and we design the off-chip “ROIC” in order to read out signal of infrared biosensor. It is necessary to apply bias voltage on pixels when infrared biosensor works, we gave a simulation of infrared biosensor in pulsed bias votage mode according to the infrared biosensor heat balance equation. Based on the simulation result, we have implemented the test system for ROIC-less and small-scale infrared biosensor array. We use FPGA as main controller to readout the infrared signal and transfer the data to PC via USB interface.

Abstract: Si_1-xGe_x/Si multi-quantum wells (MQWs) film is excellent bolometer materials, which issensitive to radiation in the 8-14 micrometer wavelength region. As an important property,temperature coefficient of resistance (TCR) reflects the quality of infrared focal plane arrays.This paper designs a MQWs temperature and resistance data automatic measurement system basedon LABVIEW, and unifies data results, the characteristics of MQWs film was analyzed anddiscussed. The task is to examine the TCR for different material-compositions of MQWs.

Abstract: A novel automatic measurement system for the TCR(temperature coefficient of resistance) test of multi quantum well which is one kind of IR and biomedical materials used in pathogen detection is presented. The system is constructed to solve the problem that conventional four-probe measurements are not suitable for multi quantum well because of the special structure of multi quantum well material. The practical application of the system demonstrates the system measurement error is less than 0.005% of the sample resistance. The results of experiment show that this system has good performances in multi quantum well measurement.