基于低温共烧陶瓷的微机械差分电容式加速度计的研究

低温共烧陶瓷（LTCC）技术是实现电子设备小型化、高密度集成化的主流封装/组装集成技术,可适用于耐高温、耐受恶劣环境下的特性要求。报道了以LTCC为结构材料设计、制作的一种MEMS差分电容式加速度计。该器件的敏感质量、4根悬臂梁结构都内嵌于LTCC多层基板,质量块和上下盖板之间通过印刷电极组成差分电容对;高精度电容检测芯片表贴于LTCC基板表面,将差分电容信号转化为电压信号。论文讨论了微机械LTCC加速度计的设计与制备、检测电路和性能测试。LTCC的高密度多层布线减小了互连线的长度和相关耦合寄生电容;基于集成芯片的检测电路解决了分立式检测电路的引起噪声大、电路复杂等问题。测试结果表明：该加速度计结构灵敏度较高,小载荷情况下表现出良好的线性关系,灵敏度约为30.3 mV/gn。     

基于MXT9030的微电容加速度计系统搭建

阐述了三明治式电容微加速度计的工作原理,并在此基础上介绍了一种具体的三明治式微加速度计的设计:采用一种通用的电容读取电路MXT9030实现对电容式微加速度传感器的信号检测,通过微控制器的控制,调节MXT9030电路的内部参数,使加速度计系统具有良好的线性度及灵敏度。实验结果表明,该设计可满足较大范围内的电容差分信号输入,并具有良好的检测灵敏度和线性度。     

非硅MEMS电容式微加速度计的测控电路设计

为了提高MEMS微加速度计的量程和抗过载能力,设计了基于UV-LIGA技术的非硅MEMS电容式微加速度计。针对该加速度计,设计了基于相敏解调的差分电容测控电路。检测通道主要由前置级电荷积分放大电路、带通滤波电路、相敏解调器、低通滤波以及电平转换电路组成,反馈通道由低通滤波和加法电路组成。完成了微加速度计测控电路的调试和检测通道的标定实验,实验表明:检测通道的量程约为±6 pF,灵敏度为89.3 mV/pF,线性度为2.59%,满足加速度计检测通道的要求。     

基于电容桥的差动电容检测方法

数字闭环石英挠性加速度计系统主要由石英挠性加速度计表头和数字检测电路组成,其极限精度取决于差动电容检测电路的灵敏度。针对数字闭环石英挠性加速度计前端差动电容检测的需求,给出了一种基于电容桥的差动电容检测方法。利用数字电路产生高频方波进行单载波调制,同时利用交流电容桥结构对载波信号进行处理,并设计后续的差分放大电路对载波信号进一步处理最终实现对微弱差动电容变化的检测。经过实验验证,检测电路对电容的检测最终实现最小分辨率约为1. 8 f F(对应加速度变化1μgn)。     

高线性度全差分四阶ΣΔ微加速度计接口ASIC

为了降低电容式Sigma-Delta（ΣΔ）微机械（MEMS）加速度计的量化噪声,减小开关电荷注入和衬底噪声共模干扰,减小谐波失真,设计了一种全差分四阶ΣΔ加速度计的接口专用集成电路（ASIC）。提出了一种简单、有效的全桥平衡结构,减小了驱动信号变化时,运放输入共模的变化对电路的干扰;提出了双侧反馈结构,大大提高了系统线性度。设计完成了电荷积分器、全差分前置补偿电路、二阶积分器等电路。采用0.5μm两层金属两层多晶n阱CMOS工艺流片,测试结果显示：闭环系统噪声密度为75μg/Hz1/2,系统灵敏度为1.32 V/gn,非线性度0.085%,功耗40 mW。结果显示本次设计满足微加速度计接口电路的设计要求。     

单载波调制型加速度计差分电容检测电路

单载波调制型差分电容检测电路是为满足微机械加速度计高线性度、高分辨率的需要而设计的,本文给出了检测电路的原理图,分析了寄生电阻、电容模型,从理论上证明该电路可有效消除寄生电阻和电容的影响,并推导了各关键功能模块的传递函数;此外,从电路的各个局部环节研究了会对电路性能造成影响的因素,包括放大电路的噪声源、载波信号稳定性、两路电荷放大器一致性、调制信号与参考信号相位同步等.经理论推导,通过改进和避免不利因素的影响即可保证电路的稳定性,适用于微机械加速度计检测领域.     

微电容加速度计系统的设计

为了在总体上把握硅微加速度计的设计,建立了叉指式硅微加速度计的机械模型,研究了全差分二阶∑-ΔADC接口检测电路提取加速度信号,优化了开关电容电路来检测微小电容变化量,运用微机电专用设计软件CoventorWare对系统的机电混合模型进行仿真,并给出数字和模拟的分析结果,为加速度计系统的机械部分和电路部分的设计提供整体的更接近实际的设计参考。     

体硅电容式双轴微加速度计的信号检测新方法

在研究体硅电容式双轴加速度计结构部分,分析差分电容检测方法的基础上,提出了一种适合该加速度计的新型信号检测方法,此方法可有效地将两轴的混叠信号分别进行输出。通过HSPICE软件仿真验证了该方法的可行性。且依据0.5μmCMOSN阱工艺参数对总体电路进行模拟仿真,5V单电源供电,微加速度计单轴灵敏度为50mV/gn,频响为2.3kHz,量程为±50gn。     

差分电容电压转换电路噪声性能分析及测试

本文对电容检测式加速度计系统中广泛采用的差分电容电压转换电路建立了电容电压转换电路的等效噪声模型,并对双运放集成电路芯片所构成的差分电容电压转换电路的本底噪声以及仪表放大器输出端的噪声进行了测试,将电容电压转换电路本底噪声中的差模噪声分量和共模噪声分量进行了分离.测试结果表明影响加速度计系统噪声性能的差模噪声分量占电容...     

差分电容硅微加速度计检测电路研究

针对硅微加速度计中微小差分电容检测,提出了一种基于调制解调方法的闭环检测电路,介绍了该闭环检测系统的原理框图和实现途径。分析了基于单路载波的前置电容-电压( C-V)转换电路,证明了基于相关芯片的解调方法的有效性,其解调效率仅对开环输出有影响;基于双路反馈电路的静电力平衡回路有效提高该检测系统的线性度。结合硅微加速度计参数和电路设计参数,对加速度计系统进行了仿真,仿真结果显示系统稳定,刻度系数为0.9 V/gn 左右,带宽700 Hz左右。结合表头进行的精密转台实验结果表明该加速度计系统刻度系数0.88 V/gn,量程可达±13 gn。     

基于LTCC工艺的数字三轴加速度传感器的研制

将微机械加工工艺与混合集成技术相结合,设计并制作了具有RS422标准接口的数字三轴加速度传感器。采用低温共烧陶瓷(LTCC)工艺将敏感元件、信号调理电路、模数转换电路和接口电路集成于一体,集成后的体积为45mm×45mm×15mm,实现了传感器的数字化、小型化和模块化,并大大提高了系统的测量精度和可靠性。     

An in-plane high-sensitivity, low-noise micro-g silicon accelerometer with CMOS readout circuitry

A high-sensitivity, low-noise in-plane (lateral) capacitive silicon microaccelerometer utilizing a combined surface and bulk micromachining technology is reported. The accelerometer utilizes a 0.5-mm-thick, 2.4/spl times/1.0 mm/sup 2/ proof-mass and high aspect-ratio vertical polysilicon sensing electrodes fabricated using a trench refill process. The electrodes are separated from the proof-mass by a 1.1-/spl mu/m sensing gap formed using a sacrificial oxide layer. The measured device sensitivity is 5.6 pF/g. A CMOS readout circuit utilizing a switched-capacitor front-end /spl Sigma/-/spl Delta/ modulator operating at 1 MHz with chopper stabilization and correlated double sampling technique, can resolve a capacitance of 10 aF over a dynamic range of 120 dB in a 1 Hz BW. The measured input referred noise floor of the accelerometer-CMOS interface circuit is 1.6/spl mu/g//spl radic/Hz in atmosphere.     

A monolithic three-axis micro-g micromachined silicon capacitive accelerometer

A monolithic three-axis micro-g resolution silicon capacitive accelerometer system utilizing a combined surface and bulk micromachining technology is demonstrated. The accelerometer system consists of three individual single-axis accelerometers fabricated in a single substrate using a common fabrication process. All three devices have 475-/spl mu/m-thick silicon proof-mass, large area polysilicon sense/drive electrodes, and small sensing gap (<1.5 /spl mu/m) formed by a2004 sacrificial oxide layer. The fabricated accelerometer is 7/spl times/9 mm/sup 2/ in size, has 100 Hz bandwidth, >/spl sim/5 pF/g measured sensitivity and calculated sub-/spl mu/g//spl radic/Hz mechanical noise floor for all three axes. The total measured noise floor of the hybrid accelerometer assembled with a CMOS interface circuit is 1.60 /spl mu/g//spl radic/Hz (>1.5 kHz) and 1.08 /spl mu/g//spl radic/Hz (>600 Hz) for in-plane and out-of-plane devices, respectively.     

灌封技术对MEMS高g加速度传感器性能影响研究

针对恶劣环境下高频信号的干扰与由封装引起的结构失效,设计了一种MEMS高g加速度传感器,通过灌封实现机械滤波,保证封装的可靠性。根据传感器封装工艺,利用ANSYS软件建立有限元模型,仿真分析了灌封技术对传感器结构和性能。结果表明：灌封技术可提高传感器的高过载能力和输出灵敏度,灌封弹性模量相对较大、密度相对较小的灌封胶可提高传感器的高过载能力和灵敏度。     

A miniature in-plane piezoresistive MEMS accelerometer for detection of slider off-track motion in hard disk drives

A miniature in-plane pizoresistive MEMS accelerometer was designed, fabricated and characterized for detection of slider off-track motion in hard disk drives. The structure of the accelerometer consists of a central supporting beam and two stress-magnifying sensing beams. Under geometric constraints imposed by the trailing side of a pico slider, the accelerometer design was optimized to achieve approximately pure axial deformation in the sensing beams and a maximum sensitivity with a specified natural frequency of 300 kHz. Fabricated on a silicon-on-insulator (SOI) wafer, the accelerometer with a half Wheatstone bridge was wirebonded to external pads and interfaced with an amplifier circuit on a printed circuit board (PCB). The noise level, sensitivity, nonlinearity were characterized with vibration testing on a shaker. The miniature accelerometer (1 × 0.3 × 0.3 mm³) with a weight of only 0.2 mg offers a much higher resonant frequency with a comparable sensitivity compared with those in previous work.     

Analysis and fabrication of a novel MEMS pendulum angular accelerometer with electrostatic actuator feedback

A new type of sensor to directly detect angular acceleration is essential for inertial and control technology. The above interest motivates us to propose a novel micro electromechanical system (MEMS) pendulum angular accelerometer with electrostatic actuator feedback. It adopts a proof pendulum with optimized moment of inertia, suspended to dual anchors by a pair of torsion spring beams, as sensing component. A pair of electrodes are designed as differential capacitors to detect the torsional angular of pendulum, then measure input angular acceleration in sensing axis. Another pair of electrodes are designed as electrostatic actuators for feedback control loop. The structure and operating principle of the MEMS angular accelerometer are introduced. Then, the structure kinetics analysis and signal detecting scheme based on differential capacitors are provided in detail, and the sensitivity and resolution of sensor are derived. Compared with the other MEMS angular accelerometers, the proof pendulum with optimized moment of inertia improves sensitivity and resolution of sensor. The electrostatic actuators feedback loop optimizes the dynamic capability and nonlinearity characteristic. The sensor is fabricated by MEMS fabrication technology. The ANSYS simulation and test results prove the validity of the theoretical analyses. The MEMS angular accelerometer can be used in industrial robots and aircraft by further implementing the signal processing electrocircuit.     

一种用于微加速度计的低输入电容运算放大器

采用0.5μm CMOS工艺设计了一种低输入电容运算放大器。该运算放大器通过采用正反馈回路消除运算放大器输入管的密勒电容来实现低输入电容。分析了寄生电容对加速度计灵敏度的影响,并提出了一种采用低输入电容运算放大器的开环加速度计接口电路实现方法。结果表明:采用低输入电容运算放大器能够有效地提高加速度计灵敏度。     

BESOI-based integrated optical silicon accelerometer

The design, simulation, fabrication and characterization of a new integrated optical accelerometer is presented in this paper. The reduction of fabrication, packaging and thermomechanical stresses are considered by keeping the weak mechanical parts free of stresses. The mechanical sensor consists on a quad beam structure with one single mass. In addition, there are two waveguides on the frame of the chip self-aligned to one on the mass of the accelerometer. Four lateral beams increase the mechanical sensitivity and allow the flat displacement of the optical waveguides on the mass. The working principle is based on the variation of the output light intensity versus the acceleration due to the misalignment of the waveguides. The devices have been optimized by the finite-element method to obtain a mechanical sensitivity of 1 /spl mu/m/g. The fabrication technology is based on BESOI wafers combining bulk an surface micromachining. Moreover, machined glass wafers with cavities are bonded to the silicon wafer for packaging and damping control. Special packaging considerations as dicing, polishing and alignment are also presented. Optical measurements at 633 nm shown an optical sensitivity of 2.3 dB/g for negative and 1.7 dB/g for positive acceleration. This difference in the sensitivity has been demonstrated as a consequence of the passivation layer located over the core of the waveguides.     

Fabrication of an hermetically packaged silicon resonator on LTCC substrate

The design, fabrication and packaging process of silicon resonators capable of the integration of LSI (Large Scale Integration) have been developed on the basis of packaging technology using an LTCC (Low Temperature Co-fired Ceramic) substrate. The structures of silicon resonators are defined by deep reactive ion etching (DRIE) on a silicon on insulator (SOI) wafer and then transferred onto the LTCC substrate and hermetically sealed by anodic bonding technique. The measured resonant frequency of a micromechanical bulk acoustic mode silicon resonator after packaging at 0.02 Pa is 20.24 MHz with a quality factor of 50,600.