基于分布式射频MEMS移相器电容开关的分析与设计

通过分析MEMS电容开关的工作原理,设计出一种适合分布式射频MEMS移相器电路的新型电容开关.采用Intel lisuiteTM软件优化电容开关的驱动电压、响应时间、释放时间和机械振动模式.结果表明,开关驱动电压为2.5 V、响应时间小于30μs,释放时间大于60 μs和所有振动模式固有频率都大于15 KHz.与普通开关结构比较,该新型电容开关结构具有优越射频机电性能和响应时间,同时也对电容开关的制备工艺进行分析.     

CAD/CAE系统中静电性能和机电性能仿真

在常规机械中很少考虑的微小静电力会对MEMS的电路产生一定影响,同时MEMS的元件在静电力作用下会发生变形,进而使得MEMS的几何结构和电容等产生变化,加之目前MEMS试制成本较高,因此,必须对整个系统的静电性能和机电性能进行分析.利用边界元素法,对MEMS各元件进行静电性能分析;采用有限元分析软件包对MEMS作机电性能分析,探讨了驱动电压与位移的关系、位移变化与电容的关系等.通过仿真测试发现,可提高设计质量,降低成本,缩短研制周期.     

基于模糊控制的MEMS陀螺仪数字驱动闭环设计

提出了基于模糊控制的微机电系统(MEMS)陀螺驱动闭环设计的方法,介绍该方法在MEMS陀螺驱动模态的应用,并在现场可编程门阵列(FPGA)平台上实现。模糊控制属于智能控制的一种,具有很强的鲁棒性、稳定性和非线性系统的控制能力。主要在于基于模糊控制的MEMS陀螺数字驱动闭环的方法,将陀螺驱动信号在FPGA的内部处理。由坐标旋转数字计算机(CORDIC)算法产生驱动及解调正弦波信号,驱动模态位移信号经过解调和低通滤波后,再由模糊控制对幅值进行恒定控制。实验结果表明:该设计方法能够使MEMS陀螺仪稳定工作在谐振状态下,幅值基本保持恒定,数字驱动闭环的响应信号幅值抖动精度可达到51×10~(-6)。     

基于MEMS微镜的混合式扫描同步设计

为了解决MEMS微镜扫描角度较小的缺点,设计了一种MEMS微镜与无刷电机同步扫描系统。该系统由STM32微控制器、 DDS驱动电路、相位检测电路组成。通过设计光栅码盘实现对无刷电机速度的测量,由PID算法控制电机转速使电机反馈信号与MEMS微镜反馈信号频率相同,并检测两路反馈信号的相位差,调节DDS驱动信号的相位实现相位同步。实验表明,系统工作稳定,相位误差不超过1.5%。     

基于CPLD和TDC的微电容传感器信号检测电路设计

针对电容传感器的工作原理,以复杂可编程逻辑器件(CPLD)为核心,采用基于时间数字转换器(TDC)技术的芯片PS021,设计了一种高精度的微小电容测量电路。给出了PS021的测量原理和电路的软、硬件设计。采用PS021结合CPLD采集处理电容信号,外围电路简洁,应用方便,软件设计通过对PS021内部可编程寄存器的合理设置实现高精度的测量。实验结果表明:电路在10 Hz刷新频率时能够达到8 aF的有效精度,最高刷新频率可达50 kHz;电路实现了1 fF～0.01 aF的分辨率,有效精度位(ENOB)可达22位;高精度高刷新率可缓和测量速度和分辨率的矛盾,提高了微小电容的测量精度。     

基于绝缘液体充填封装RFMEMS开关特性分析

提出并设计一种采用绝缘液体充填封装的RF MEMS开关,分析其工作原理,并以高压油、蓖麻油、甘油为绝缘液体充填封装,仿真分析绝缘液体对RF MEMS开关的驱动电压、冲击速度、响应时间、开关电容等方面的影响。结果表明:绝缘液体充填封装有效地将驱动电压降为原来的1/εr,降低上极板对下极板的冲击速度。对3种液态封装材料性能分析,蓖麻油效果最好:阈值电压下降了一半,约为10 V;当驱动电压为20 V时,响应时间为40.6μs,优于高压油(91.3μs)、甘油(89.9μs),冲击速度约为1.26 m/s。     

MEMS集成滤波器技术

滤波器是频率转换系统(如,调谐电路、接收器)的基本构成模块。借助于MEMS技术实现的滤波器不仅带来插入损耗、功耗、线性等性能的改善,也有利于将整个通信前端集成到单一芯片上。综述了MEMS可调滤波器的研究进展。与单一利用MEMS电容的调变实现频率可调的滤波器相比,分形可调MEMS滤波技术有更小的插入损耗和更宽的调频范围。     

提高光栅数字地震检波器精度的方法研究

在地震勘探系统中,随着数据记录系统动态范围的突破,地震检波器的动态范围已不能满足系统的要求,提高检波器的精度和动态范围变成地震勘探技术研究的关键.光栅数字地震检波器的研制成功,提高了检波器的精度和动态范围.通过对光栅传感器机理的深入分析,采用5细分专用芯片为核心的细分电路,成功实现了光栅脉冲信号的20倍细分技术.在采用100线计量光栅的情况下,使检波器分辨率达到0.000 5 mm,动态范围达到75dB.并采用PIC单片机系统完成了振动信号的再现.该方法将有助于光栅数字地震检波器的性能完善,为实现高精度地震勘探技术奠定基础.     

低驱动电压k波段电容耦合式RFMEMS开关的设计

设计了一种低驱动电压的电容耦合式射频微机械(RF MEMS)开关.RF MEMS开关采用共面波导传输线,双电极驱动,悬空金属膜采用弹性折叠梁支撑.使用MEMS CAD软件CoventorWare、微波CAD软件HFSS,分别仿真了开关的力学性能和电磁性能,仿真结果表明:开关的驱动电压为2.5V,满足低驱动电压的设计目标;开关开态的插入损耗约为0.23 dB@20 GHz,关态的隔离度约为18.1 dB@20 GHz.最后给出了这种RF MEMS开关的微制造工艺.     

基于TDC的微小电容测量电路的设计

提出一种基于TDC(时间数字转换)的微小电容测量电路的设计方案。该电路具有功耗低、体积小、抗干扰性强、分辨力高、刷新率高的特点。详细阐述了测量电路的基本原理、具体实现、参数配置、标定和抗干扰设计,并且通过测量0pF～3pF范围的固定电容和动态电容验证了电路的性能。试验表明电路在10Hz刷新频率下分辨力为6aF;电路在13kHz刷新频率下分辨力为610aF;ENOB(有效精度位)最高可达22位。     

电容式微机械陀螺接口电路

接口电路是电容式微机械陀螺研制中的关键技术之一.给出了一种通用的电容式微机械陀螺接口电路方案.该方案包括电容检测和信号处理两个模块.相位相反幅度相同的两路高频载波加在敏感差动电容的两端形成敏感电桥,另一频率的高频载波叠加了驱动信号后加在驱动差动电容两端形成驱动电桥,质量块作为所有电容的公共端连接两电桥接虚地的放大器,构成前置电容检测模块;后续的带通滤波电路将驱动和敏感信号分离,各自解调滤波得到两个模态相应的振动信息,驱动振动对敏感振动再次解调即可得到和输入角速度信号成线性关系的直流电压.采用音叉电容式陀螺进行实验,结果表明该电路能够有效的能够有效的抑制寄生电容和各个接口电容之间电耦合的,电容分辨率可以达到10-15F.     

Testing of MEMS capacitive accelerometer structure through electro-static actuation

The present paper discusses a method for testing a MEMS capacitive accelerometer structure through electrical actuation. The response of a standard MEMS capacitive accelerometer structure for different electrical actuation voltages has been analyzed. The accelerometer structure along with a capacitance sensing integrated circuit (IC) MS3110 is modeled and simulated. A set of proto-type accelerometer structures is fabricated and packaged in PGA packages. The packaged MEMS structures and MS3110 IC are integrated on a printed circuit board. The MEMS structure is actuated by applying the electrical signal through the actuation fingers and the change in capacitance is measured by the MS3110 IC. The simulated and measured results show some interesting phenomenon like dipping and frequency doubling which are useful for initial testing and characterization of a MEMS accelerometer structure.     

基于数字控制线性可调OTA的FPAA

提出了一款基于差分式数字控制线性可调跨导运算放大器（POTA）的低功耗、高性能的现场可编程模拟阵列（FPAA）。可重构模拟单元（CAB）采用差分式POTA电路,提高了电路高频性能和抗共模干扰能力。为了减少通用电容矩阵中寄生电容对电路性能的影响,设计了一款电容倍增器。采用六边形互连网络拓扑结构和开关共享技术,使各CAB之间实现了较好的可编程能力,同时减少了可编程开关数量及开关噪声对电路性能的影响。作为应用,在4[×]7阵列结构上重构实现了一个可调谐六阶巴特沃斯通用滤波器,通过调节相应开关的控制字可实现电路拓扑结构和参数的改变,从而实现不同的滤波类型和极点频率的调节。电路的性能通过Pspice仿真得到了验证。     

A top-down design methodology of MEMS varactor for RF applications based on a substrate-induced capacitive model

Due to their excellent quality factor in microwave frequency range, microelectromechanical (MEMS) varactors are an attractive choice for wireless communication engineers for building high performance telecommunication circuits. Significant progress in the technology of MEMS varactor has been reported over the past few years; however a comprehensive design methodology for the varactors based on some performance specifications is not reported. Also, it has been found that for the varactors fabricated with multi user processes (MUMPs), the measured capacitance deviates widely from the predicted value. In this work, it has been shown that a substrate-induced capacitance can change the expected capacitance of the varactor widely and can justify the deviation of the measured values to a good degree of accuracy. Here, a quantitative account of this difference has been presented. The capacitance profile of the varactor fabricated in PolyMUMPs process has been measured and the results show good agreement with the design values; thus indicating a clear influence of substrate induced capacitance on the varactor. Finally, a systematic design methodology of the varactor for a voltage controlled oscillator (VCO) application has been given.

     

A top-down design methodology of MEMS varactor for RF applications based on a substrate-induced capacitive model

Due to their excellent quality factor in microwave frequency range, microelectromechanical (MEMS) varactors are an attractive choice for wireless communication engineers for building high performance telecommunication circuits. Significant progress in the technology of MEMS varactor has been reported over the past few years; however a comprehensive design methodology for the varactors based on some performance specifications is not reported. Also, it has been found that for the varactors fabricated with multi user processes (MUMPs), the measured capacitance deviates widely from the predicted value. In this work, it has been shown that a substrate-induced capacitance can change the expected capacitance of the varactor widely and can justify the deviation of the measured values to a good degree of accuracy. Here, a quantitative account of this difference has been presented. The capacitance profile of the varactor fabricated in PolyMUMPs process has been measured and the results show good agreement with the design values; thus indicating a clear influence of substrate induced capacitance on the varactor. Finally, a systematic design methodology of the varactor for a voltage controlled oscillator (VCO) application has been given.     

A MEMS reconfigurable DGS resonator for K-band applications

A MEMS reconfigurable defected-ground-structure (DGS) resonator using two-dimensional (2-D) periodic DGS for coplanar waveguide (CPW) transmission line and RF MEMS series-resistive switches is proposed. The introduced MEMS reconfigurable DGS resonator has approximately a fixed bandwidth of 8.1 GHz over a wideband frequency range (K-band). The proposed structure can be designed easily for other frequency bands by changing the number of unit-cells of the 2-D PDGS. A cascaded two parallel-resonance circuit model for the MEMS reconfigurable DGS resonator has been introduced as well. The equivalent circuit parameters extraction methods have also been derived. Simulations based on the proposed circuit model are in a very good agreement with the electromagnetic (EM) simulations, which suggests that the MEMS reconfigurable DGS resonator is an inductive controlled reconfigured structure. The structure is designed in CPW environment on a high-resistivity silicon substrate. It is therefore suitable for monolithic integration with standard IC process.     

一种基于FPGA高集成化的直接数字频率合成系统的设计

文章提出了一种基于高集成化的直接数字频率合成技术构成的程控信号发生器的设计方案，用于模拟微硬盘读写通道的伺服信号，方案采用超大规模FPGA（field-programmable logic）集成PDSP（programmable digital signal processor）设计和直接数字频率合成技术，试验结果证明，与传统使用分离器件设计方案相比，该方案能产生较高质量信号。电路设计有集成化、低功耗，简单化、易现场修改、便于程控等优点。     

Accurate Simulation of RF MEMS VCO performance including phase noise

A new coupled circuit and electrostatic/mechanical simulator (COSMO) is presented for the design of low phase noise radio frequency (RF) microelectromechanical systems (MEMS) voltage-controlled oscillators (VCOs). The numerical solution of device level equations is used to accurately compute the capacitance of a MEMS capacitor. This coupled with a circuit simulator facilitates the simulation of circuits incorporating MEMS capacitors. In addition, the noise from the MEMS capacitor is combined with a nonlinear circuit-level noise analysis to determine the phase noise of RF MEMS VCO. Simulations of two different MEMS VCO architectures show good agreement with experimentally observed behavior.     

微小差分电容检测电路设计

针对电容式MEMS器件,设计了一种用来检测微小差分电容的电路,该电路主要有方波信号发生器、相敏解调和低通滤波电路等组成.具有抗干扰性能好、电路简单、易于集成的特点.通过主要器件--运放的合理选择,调试出较理想的结果.经实验验证,其分辨率可达10-16F.     

MEMS石英振梁高增益谐振电路的设计与分析

介绍了一种基于新型高阻抗QVBA的高增益谐振电路设计和谐振电路的分析测试实验。利用阻抗分析仪4294A测得石英振梁的等效参数,对石英振梁的电气特性进行分析,发现高阻抗石英振梁起振比普通晶振需要更高增益。基于双门振荡电路,利用运算放大器在开环系统中具有无限增益的理论,提高谐振电路的驱动能力。同时采用谐波抑制网络,指出谐波抑制网络可以抑制无用的频率避免传感器输出信号出现泛音频率,并提高谐振电路的稳频速度。考虑电噪声对输出波形质量的影响,在电路的输入部分采用滤波电容,并在电路的输出部分采用反向器整形,使电路输出标准的方波信号。最后利用安捷伦DSO5012A型号示波器和频率计对高增益谐振电路和石英振梁组成的谐振系统进行测试,测试结果表明本文设计的谐振电路与石英振梁组成的谐振系统可以输出标准的方波信号,输出频率精度达到10-5 kHz,在振动稳定以后频率变化小于0.1 Hz,无泛音频率出现,对研究高精度MEMS加速度计传感器具有重要意义。