串联电容式RF-MEMS开关的研制

研制了一种高电容率的电容式RF-MEMS开关.与普通电容式开关设计不同的是,在CPW信号线上的绝缘层上表面覆盖了一层金属板,使开关在down-state时,上电极能与介质膜紧密接触,而在up-state时,金属板分别与上电极及信号线平面构成一组串联电容,大大降低了Cup值,从而提高了开关的电容率.与相同条件制得的普通电容式开关相比,其电容率要高出一个数量级,达到1000以上.由测试可知,所设计的串联电容式开关其隔离度在8GHz时可达42dB,明显优于普通电容式开关.     

RF MEMS开关的设计分析

针对具有低损耗、高隔离度性能的微机电系统(Micro-Electro-Mechanical System,MEMS)开关,介绍了串联DC式和并联电容式的开关结构模型,并对并联电容式MEMS开关的工作原理、等效电路模型和制造工艺流程进行了描述,利用其模型研究了开关的微波传输性能,设计了一款电容耦合式开关并进行了仿真。由仿真结果可得,开关"开态"时的插入损耗在40 GHz以内优于-0.3 dB;开关"关态"时的隔离度在20～40 GHz相对较宽的频带内优于-20 dB。     

基于C-V,I-V,Q-V特性的铁电电容新模型

推导出描述铁电电容电气特性的新模型.铁电电容可以等效为开关电容(电畴电容)和非开关电容(普通线性电容)的并联,而电畴电容可以看作是由电偶极子组成的铁电材料、上电极和下电极组成.根据实验测试的铁电电容的C-V特性,选定电偶极子矫顽电压的概率密度函数为t分布,从而推导出只用6个参数描述的铁电电容的C-V,I-V和Q-V关系式,根据这些关系式仿真的结果与实验结果基本吻合.     

集成电容式传感器边界电极的静电电容值分析

 本文研究一种梳齿电极结构的集成电容式传感器,利用保角变换对其边界电极的静电电容值情况进行推导,给出了边界电极电容值的解析表达式,并利用Ansys软件对其进行仿真验证。结果显示解析公式得到的计算结果和软件仿真结果相吻合,说明得到的公式具有高的精度。利用所给的解析表达式可以为设计和应用该结构电容式传感器提供更好的理论基础。     

基于液体摆的双轴电容式倾角传感器

为了克服现有倾角测量传感器制作工艺复杂、价格昂贵和操作困难的缺点,根据液体在电极间流动时电容的变化,设计了一种液体摆双轴电容式倾角传感器,推导了传感器的偏转角度与电容值之间的关系模型,并对传感器在单轴和全方位偏转角度下的响应进行分析.测试结果表明,此传感器在内轴和外轴上的灵敏度分别为0.0215 pF/°和0.0347...     

一种新型三谐振点电容式RF MEMS开关

给出了改进的电容式开关等效电路模型以及基于该电路模型的一种新型的多频段工作的电容式RFM EM S开关的设计和制作研究。分析表明,当开关的上电极为多支撑梁结构时,需要对传统的开关等效电路加以改进。利用新型等效电路模型进行模拟发现,通过适当的参数选择,可以获得多谐振点开关,不仅可以在多个频段适用,并且可以适用于较低频段。设计了一种可工作在X波段下的三谐振点电容式RF MEMS开关,并在高阻硅衬底上采用表面微加工工艺制备了开关样品。三谐振点开关的在片测试结果为:驱动电压为7 V,“开”态的插入损耗为0.69 dB@10.4 GHz,“关”态的隔离度为30.8 dB@10.4 GHz,其微波性能在0~13.5 GH z频段下优于类似结构的传统单谐振点开关。     

低驱动电压电容式RF MEMS开关结构设计优化

RFMEMS开关将成为微波、高频信号控制的关键器件。针对其驱动电压过高,不能满足现代通信系统低电压的要求,推导了电容式RFMEMS开关驱动电压的理论公式;基于降低开关柔顺结构的弹性系数、驱动电极上极板与可变电容上极板分离的思路,优化设计了三种具有不同的连接梁和支撑梁结构形式的开关微桥柔顺结构。第一种结构为驱动电极板和电容上极板之间以双直梁连接;第二种结构以一组弹性折叠梁代替结构一中的双直梁;第三种结构是在结构二的基础上,改变了起支撑作用的弹性折叠梁的方向。使用MEMS CAD软件CoventorWare对开关结构进行了机电耦合仿真,仿真结果表明开关的驱动电压小于3V。     

一种双波段MEMS低噪声放大器设计

本文利用一种MEMS电容式开关并联实现双波段2．1GHz／4．6GHz微机械低噪声放大器。根据MEMS电容开关的电容特性,实现LNA电路匹配阻抗的变化、在不同的波段实现谐振匹配,从而实现双波段分别放大的功能。首先提出一种电容式开关的设计,理论、仿真分析了开关的特性,开关在2．21GHz和4．8GHz具有良好的插入损耗和隔离度、插损为2．2dB左右,隔离度达到30dB以上。其次将开关引入于基于Casoode放大管的LNA电路中、和CMOS电路具有很好的兼容性,设计了LNA的电路模型和仿真分析、分析结果表明,在频率为2．21GHz时、增益达到11．4dB,4．8GHz时、增益达12．5dB,二波段隔离度在30dB以上、噪声在4．1dB左右,该研究方法和设计克服了普通双波段LNA需要两路单独电路的缺点,该器件可应用在Wimax,WiFi等3．5G、4G无移动通信网络中。     

电容放电式火工品发火电压检测仪

针对电容式放电火工品发火电压检测自动化生产的要求,设计了一种基于电容放电式的火工品发火电压检测仪,该系统硬件平台以单片机STM8为核心,集成了数控步进调压电源,电容放电发火电路模块,并设计了放电开关驱动电路以提高开关导通速度,提高电容能量的释放效率。实验结果表明该测试仪能模拟电容放电式火工品的发火过程,操作简便,满足其测试精度。     

基于C-V,I-V,Q-V特性的铁电电容新模型

推导出描述铁电电容电气特性的新模型．铁电电容可以等效为开关电容（电畴电容）和非开关电容（普通线性电容）的并联,而电畴电容可以看作是由电偶极子组成的铁电材料、上电极和下电极组成．根据实验测试的铁电电容的C-V特性,选定电偶极子矫顽电压的概率密度函数为t分布,从而推导出只用６个参数描述的铁电电容的C-V,I-V和Q-V关系式,根据这些关系式仿真的结果与实验结果基本吻合．     

BST-MEMS移相器开关

为了提高MEMS电容开关性能,介绍了移相器的一种新型结构——分布式电容周期性加载结构。分析发现移相器的相移度和单元可变电容的变化率有关。目前MEMS可变电容单元采用的介质基本上是氮化硅。BST薄膜作为一种性质优良的介电材料,其介电常数远大于氮化硅。从MEMS移相器开关性能的几个关键指标出发,探讨在MEMS移相器开关中,用BST薄膜代替氮化硅介质的可能性。     

Noncontact measurement of charge induced voltage shift in capacitive MEM-switches

The use of a modulated microwave signal to directly measure the voltage shift induced by charge in the dielectric layer of a capacitive microelectromechanical (MEM) switch is presented. This method does not require the metal bridge to contact the dielectric layer and is thus much less intrusive than previously reported measurements. The technique is a useful tool for understanding charge build up and dissipation in capacitive MEM switches.     

DCDC—20GHz射频MEMS开关

描述了 DC— 2 0 GHz射频 MEMS开关的设计和制造工艺 .开关为一薄金属膜桥组成的桥式结构 ,形成一个单刀单掷 (SPST)并联设置的金属 -绝缘体 -金属接触 .开关通过上下电极之间的静电力进行控制 ,其插入损耗及隔离性能取决于开态和关态的电容 .测试结果如下 :射频 MEMS开关驱动电压约为 2 0 V,在“开”态下 DC— 2 0 GHz带宽的插入损耗小于 0 .6 9d B;在“关”态下在 14— 18GHz时隔离大于 13d B,在 18— 2 0 GHz时隔离大于 16 d B.本器件为国内首只研制成功的宽带射频 MEMS开关     

Alpha particle radiation effects in RF MEMS capacitive switches

The paper investigates the effect of 5 MeV alpha particle irradiation in RF MEMS capacitive switches with silicon nitride dielectric film. The investigation included MIM capacitors in order to obtain a better insight on the irradiation introduced defects in the dielectric film. The assessment employed the thermally stimulated depolarization currents method for MIM capacitors and the capacitance–voltage characteristic for MEMS switches. Asymmetric charging was monitored in MIM capacitors due different contact electrodes and injected charge interactions.     

高隔离度X波段RF MEMS电容式并联开关

研究了一种新型的、应用于X波段的高隔离度RF MEMS电容式并联开关结构。相比于普通的并联结构,该开关通过共面波导(CPW)传输线与地平面之间的衬底刻槽结构将隔离度提高了7dB,关态时在13.5GHz谐振频率处的隔离度为-54.6dB,执行电压为26V。弹簧梁结构开关的执行电压下降为14V,在11GHz处其隔离度为-42.8dB。通过两个并联开关级联与开关间的高阻传输线构成的π型调谐开关电路,在11.5GHz处的隔离度为-81.6dB。     

All-metal high-isolation series and series/shunt MEMS switches

This paper presents a novel all-metal series switch with several different pull-down electrode geometries. The switch results in an up-state capacitance of 5-9 fF and an isolation of -25 to -30 d8 at 10 GHz. The fabrication process is completely compatible with the standard capacitive (or dc-contact) shunt switch, A dc-30 GHz series/shunt switch is also presented with an isolation of -60 dB at 5 GHz and -42 dB at 10 GHz. This is the highest isolation switch available to-date. The performance is limited by radiation in the CPW lines and not by the series/shunt switch characteristics. The application areas are in high-isolation switches for basestations and satellite systems     

Temperature study of the dielectric polarization effects of capacitive RF MEMS switches

This paper investigates both theoretically and experimentally the dielectric charging effects of capacitive RF microelectromechanical system switches with silicon nitride as dielectric layer. Dielectric charging caused by charge injection under voltage stress was observed. The amphoteric nature of traps and its effect on the switch operation were confirmed under both positive and negative control voltages. It has been confirmed that charging is a complicated process, which can be better described through the stretched exponential relaxation. This mechanism is thermally activated with an activation energy being calculated from the temperature dependence of the capacitance transient response. The charging mechanism, which is responsible for the pull-out voltage and the device failure, is also responsible for the temperature-induced shift of the capacitance minimum bias.     

Novel high-isolation FET switches

This paper describes novel high-isolation monolithic microwave/millimeter-wave integrated circuit (MMIC) field-effect transistor (FET) switches that have higher isolation characteristics than conventional switches without much insertion loss degradation. The newly developed switches consist of series/shunt FETs and T-shaped R-C-R circuit. Each FET switch utilizes the parasitic capacitive component of the FETs in the off-state to produce a band-rejection filter at the operating frequency. The design method of the newly proposed switches and their characteristics are described herein. With this method, the isolation characteristics are improved by more than 15 dB between 5.4 GHz and 6.4 GHz and more than 20 dB between 5.5 GHz and 6.1 GHz over conventional values     

Determination of bulk discharge current in the dielectric film of MEMS capacitive switches

The present work presents a new method to calculate the discharge current in the bulk of dielectric films of MEMS capacitive switches. This method takes into account the real MEMS switch with non uniform trapped charge and air gap distributions. The assessment of switches with silicon nitride dielectric film shows that the discharge current transient seems to obey the stretched exponential law. The decay characteristics depend on the polarization field’s polarity, a fact that comes along with experimental results obtained from the thermally stimulated depolarization currents (TSDC) method used in MIM capacitors.     

高隔离度S波段MEMS膜桥开关

常规的 MEMS膜桥开关在 1 0 GHz以上频段才具有低插损、高隔离度 (>2 0 d B)的优点。文中介绍了一种应用于微波低频段—— S波段的高隔离 MEMS膜桥开关 ,给出了开关的设计与优化方法 ,建立了开关的等效电路模型。通过双膜桥结构、选择高介电常数的介质膜、微电感结构膜桥这些措施 ,达到提高开关隔离度的目的。利用 HFSS软件仿真的结果表明 ,该开关在微波低频段 (3～ 6GHz)有着很好的隔离性能。开关样品在片测试的电性能指标 :插损 <0 .3 d B,隔离度 >40 d B,驱动电压 <2 0 V