Key Engineering Materials Vols. 609-610

Abstract: A silicon thermal flow-sensor system based on ceramic substrate is described in this paper. The sensor chip is mounted on a ceramic substrate with a metal heat sink. The simulation by ANSYS software and the experiment are done for determining suitable package size. The results from the ANSYS simulation and the standard flow test in the flow tunnel show that when the radius of the ceramic is 10mm and the heat conduction is 35Wm^-1K^-1, the performance of the sensor is much better. The heat sink will make the flow-sensor more stable. The wind speed up to 35m/s and the precision of 0.5m/s are acquired in this experiment.

Abstract: This paper reports the two dimensional (2D) magnetic sensor, which is comprised of twoMOSFET Hall devices with similar characteristics. The sensor is based on the MOSFET Hall deviceprinciple and is fabricated on <100> orientation silicon substrate by adopting complementary metaloxide semiconductor (CMOS) technology and packaging technology. The experiment results indicatethat when VDS =5.0 V, the magnetic sensitivities of the 2D magnetic sensor can reach Sx=34.0 mV/Tand Sy=33.6 mV/T in the x and y directions, respectively, it is necessary to realize the measurementof 2D magnetic field.

Abstract: In this Paper, a 4th-Order Low-Pass Gm-C Filter is Presented. for the Design of Operational Tranconductance Amplifier(OTA), it Adopts the Techniques of Current Division and Current Cancellation. these Techniques can Help to Achieve a Low Transconductance Value. for the Architecture of the 4th-Order Gm-C Filter, it Consists of Two Biquads. the Two Biquads are Cascade Connected. the Gm-C Low-Pass Filter has been Implemented under 0.5 μm CMOS Process Model. the Final Simulation Results Show the Cutoff Frequency of the Filter is 100Hz and the Stop-Band Attenuation is Larger than 60dB. the Power Consumption is Lower than 1mW and the Total Harmonic Distortion(THD) is -55dB.

Abstract: In this paper, a 4^th-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 4^th-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.

Abstract: In this paper, we presented Hall magnetic sensors based on nano-polysilcon thin film transistors(TFTs). These sensors are fabricated on the <100> orientation high resistivity silicon substratesby using complementary metal oxide semiconductor (CMOS) technology and adopting thenano-polysilicon thin films with thickness of 82 nm as the channel layers of TFTs. The influence ofthe channel layer doping type and channel length-width radio of TFT on sensor's sensitivity was investigated.When the supply voltage is 5.0 V, the maximum measured sensitivity of p-type channel andn-type channel sensors are about 8.5 mV/T and 25.6 mV/T, respectively. These experimental resultsmean that nano-polysilicon thin films present an application on Hall magnetic sensors.

Abstract: A silicon bridge magnetic sensor based on cantilever beam is presented in this paper. Thesensor is composed of the Wheatstone bridge that made up of nano-polysilicon thin-film transistors(TFTs) and a ferromagnetic magnet adhered to the free end of cantilever beam. Through building thesimulation model, the finite element analysis of the sensor is carried out by using ANSYS software.The results show that this sensor can realize the measurement to the external magnetic field. Accordingto the simulation results, fabrication and packaging of the sensor chip are achieved by using the microelectromechanical system (MEMS) technology. Experiment result shows that when the supply voltageis 3.0 V, the sensitivity of the sensor is 94 mV/T.

Abstract: A two-dimensional position sensitive detecting sensor (PSD) based on avalanche breakdown is introduced in this paper. The structure of the sensor is designed under the assumption that the breakdown of the PN junction in the sensor occurs at the bottom of the PN junction. The breakdown structure and characteristics of the sensor are simulated by Medici software and the doping structure and process conditions are calculated by Tsuprem4 software. By using COMSOL Multiphysics, we obtained current allocation of the straight and right angle type electrodes, which is corresponding to the optimal structure. In simulation, the root mean square error of the rectangular-shaped electrode and the straight line-shaped electrode are 0.198, 0.145 respectively. Experiment results show that in the 50% photosensitive area with the center as the origin, the rectangular-shaped electrode error is much smaller than a straight line-shaped electrode and fits in to linear relationship better. But the error of the angle the boundary of the electrode is significantly worse than the line-shaped electrode.

Abstract: A silicon bridge magnetic sensor based on nano-polysilicon TFTs is presented in this paper.It adopted four nano-polysilicon TFTs on the center of every squared silicon membrane edge to forma Wheatstone bridge, and then its squared silicon membrane center was sticked by ferromagnetic material.The sensor simulation was realized by adopting ANSYS software. The simulation results showthat based on the piezoresistive effect, the measurement to the external magnetic field can be achieved.According to the simulation results, we designed and fabricated the silicon bridge magnetic sensor byCMOS technology and MEMS technology. The experimental results show that when supply voltageof the sensor is 5.0 V, its full range (4.0 kGs) output voltage is 10.97 mV, and magnetic sensitivity is1.44 mV/kGs.

Abstract: Mathematical model of sensitive structures and detection principle of Sigma-Delta accelerometer are analyzed in this paper, and then an accelerometer with SNR 107dB is designed using MATLAB, the stability of which is analyzed based on root locus plot. When input is small than-3dBFS, the system is unsaturated. The poles and zeros of accelerometer noise transfer function are then analyzed and the feed-forward coefficient and local feedback coefficient are optimized, achieving a higher SNR of 112.1dB. At last, the circuit-level simulation is conducted and in-band noise level is about-140dB.

Abstract: The new structure of in-plane high-g MEMS sensor for 10,000-150,000g has been designed in our paper, and it was packaged in dimensions of 17.5mm×12mm×4.5mm. In our experiments, the sensitivity reach to 0.335uv/g by the Hopkinson bar system and it also is in quick respose to the frequence. Meanwhile, the results show that all acceleration-time pulses are in very close agreement for acceleration amplitudes to about 150000g. It is a new way to monolithically integral triaxial piezoresistive high-g accelerometer in the future.