一种超宽带MEMS开关的研制

MEMS射频器件,特别是超宽带器件,对其中的射频器件提出了宽带指标的要求。以此为背景,在理论分析的基础上设计了一种应用于12.5 GHz~50 GHz频带的超宽带双膜桥式MEMS开关,该开关具备低损耗、高隔离度等特点,文中给出了开关的制备工艺,并进行流水完成了芯片制备。经测试,该开关在设计频段内,回波损耗优于20 dB,插入损耗典型值0.3 dB@12.5~35 GHz,优于0.5 dB@45 GHz,隔离度全频段优于20 dB,驱动电压在45 V~55 V之间。     

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.     

RF MEMS悬臂梁开关的设计与仿真

利用有限元软件HFSS和ANSYS系统研究了串联MEMS开关的微波性能和力学性能与其结构参数之间的关系,并在此基础上优化出悬臂梁开关的几何结构参数,设计了RF MEMS开关,实验表明：在外施电压为10V左右时,悬臂梁的挠度可达3μm左右,5GHz时,回波损耗小于0．2dB,隔离度大于35dB。     

RF MEMS开关在牺牲层工艺上的改进

通过对传统的RF MEMS开关采取在信号线上电镀桥墩、改进桥梁的形状以及在桥背面设计接触点的新颖方法,使得RF MEMS开关的下拉电压减小、开关时间缩短和可靠性提高.在工艺上,特别采用了对聚酰亚胺牺牲层进行全刻蚀和半刻蚀的改进加工流程来实现桥背面的接触点.测试结果表明:开关的下拉电压为28V,最低开关时间为0.8μs,开关寿命达7×105次,0～10GHz的插入损耗在0～0.5dB,隔离度为35～45dB.     

不同设计参数对SOI射频开关小信号的影响

基于0.2μm SOI RF工艺平台,设计了串联支路、并联支路、单刀单掷、单刀双掷等电路结构,分析研究了单级宽度、级联数目、偏置电阻、偏置电压等设计参数对射频开关小信号特性的影响。通过实验数据,讨论各参数对射频开关小信号特性,主要包括射频开关的插入损耗和隔离度的影响,为射频开关设计提供参考。     

介质层充电对电容式RF MEMS 开关的影响

电容式RF MEMS开关介质层电荷累积被认为是导致开关失效的主要原因.基于电容式RF MEMS开关工作过程中电场强度的变化,分析讨论了累积电荷的来源,并推导出相应的计算公式.对于随机性较大的界面极化问题,根据理论计算公式,提出从工艺上减小极化现象发生的解决方案.在讨论影响介质层电荷注入各种因素及相互之间关系的基础上,建立了基于电荷累积的开关寿命预测模型.     

电容式RF MEMS开关开关过程产生的电磁波模型和分析

在电容式RF MEMS开关的动态工作过程中,会有电磁波产生.根据开关膜桥的动态运动模型,把开关工作分成了四个过程,并通过麦克斯韦方程建立了各个过程中产生的电磁波模型,最后通过单元面叠加的方法验证了这一模型.在开关电容充电和膜桥下拉过程中,开关都是产生了电磁波脉冲.尤其是在充电阶段,电磁波峰值为105 A/m的量级,持续时间为3.15×10-8μs.而在开关电容放电过程中,产生的电磁波是时谐波,其频率为23.4 GHz(落在RF信号的频率范围内了).这就提醒了设计者们要增加特殊的滤波电路来过滤掉RF信号中噪声.此外,辐射的电磁波同样对开关周围的电路和器件有影响,这需要进一步的研究.     

高介电常数介质RF MEMS开关的制作研究

介绍了一种电容式MEMS开关的制作工艺.所有的步骤都采用表面微加工工艺完成.其中,区别于常规采用的SixNy薄膜,笔者采用了高介电常数的Ba0.5Sr0.5TiO3(BST)铁电薄膜作为开关的介电层,使"开""关"状态电容比值大大提高,开关的插入损耗和隔离度性能得到提高.在制作工艺上,采用正胶作为牺牲层,并用发烟硝酸进行释放,获得了较好的效果.最终,制备了一种高性能的电容式MEMS开关.     

一种低驱动电压的SP4T RF MEMS开关

设计并制备了一种低电压的静电驱动接触式单刀四掷(SP4T)RFMEMS开关。单元开关采用以低应力氮氧化硅(SiON)作为桥膜的双端固定桥式结构,并利用附着的金层形成接触结构。整个SP4T开关包括与50Ω特征阻抗相匹配的共面波导,1个输入端,4个输出端,4个静电驱动的侧拉桥,以及4个驱动引出区(pad)。测试数据表明,开关驱动电压18.8V;插入损耗S21<0.26dB@DC-3GHz,S31<0.46dB@DC-3GHz;隔离度S21>69.5dB@DC-3GHz,S31>69.2dB@DC-3GHz。结果显示,此开关的隔离度在所有输出端有很好的一致性,插损在DC-3GHz的频段内均较小,非常适合低频使用。     

扭转臂杠杆式MEMS膜开关的分析

为解决现有的MEMS微波开关的激励电压太高、微连接和膜开关的击穿电压等问题,提出了一种独特结构的MEMS微波开关—扭转臂杠杆式膜开关,并对其进行了理论分析,用conventorware和ADS(ad vanceddesignsystem)软件进行了仿真。由于利用了膜结构以及扭转臂和杠杆的原理,这种独特的MEMS微波开关激励电压比较低、隔离度较高、插入损耗比较低、稳定性好。     

MEMS capacitive series switch fabricated using PCB technology

In this article, an RF MEMS capacitive series switch fabricated using printed circuit processing techniques is discussed. Design, modeling, fabrication, and characterization of the CPW series switch are presented. An example CPW series capacitive switch with insertion loss less than 0.5 dB in the frequency range of 13–18 GHz and isolation better than 10 dB up to 18 GHz is discussed. The switch provides a minimum insertion loss of about 0.1 dB at the self‐resonance frequency of 16 GHz and a maximum isolation of about 42 dB at 1 GHz. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Design and simulation of a thermally actuated MEMS switch for microwave circuits

The design, modeling, and optimization of a novel, thermally actuated CMOS‐MEMS switch are presented in this article. This series capacitive MEMS switch solves the substrate loss and down‐state capacitance degradation problems commonly plaguing MEMS switches. The switch uses finger structure for capacitive coupling. The vertical bending characteristic of bimorph cantilever beams under different temperatures is utilized to turn the switch on and off. A set of electrical, mechanical, and thermal models is established, and cross‐domain electro‐thermo‐mechanical simulations are performed to optimize the design parameters of the switch. The fabrication of the switch is completely CMOS‐process compatible. The design is fabricated using the AMI 0.6 μm CMOS process and a maskless reactive‐ion etching process. The measured results show the insertion loss and isolation are 1.67 and 33 dB, respectively, at 5.4 GHz, and 0.36 and 23 dB at 10 GHz. The actuation voltage is 25 V and the power consumption is 480 mW. This switch has a vast number of applications in the RF/microwave field, such as configurable voltage control oscillators, filters, and configurable matching networks. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

A novel DMTL capacitive switch with electrostatic actuation MAM capacitors

A novel DMTL capacitive switch with electrostatic actuation metal–air–metal (MAM) capacitors is presented. The top board of MAM capacitors will be pulled down together with the switch bridge. It has higher isolation in down-state than DMTL capacitive switch and has lower insert loss and higher self-actuation RF power comparing with MEMS shunt capacitive switch. Two of the novel DMTL capacitive switches are designed for high isolation and high self-actuation RF power, respectively. The calculated result shows that both of the two novel switches have lower insert loss than the MEMS shunt capacitive switch. The self-actuation RF power of them are 4 and 2.4 times that of MEMS shunt capacitive switch, respectively, at the cost of ?6.23 and ?3.54?dB reduction in isolation (30?GHz).     

RF MEMS电容式开关结构层释放技术

研究了RF MEMS开关的制造工艺流程和聚酰亚胺牺牲层的去除工艺。在开关的设计和加工中采用在信号线两侧的地线上生长一层绝缘介质层,直流偏置线生成在绝缘介质层之上,与桥的锚点相连接,实现了交直流隔离。讨论了干法刻蚀和湿法刻蚀牺牲层技术。干法刻蚀容易造成绝缘介质层的刻蚀和损伤。采用湿法刻蚀结合临界点干燥技术,可以获得理想的微梁结构。通过测试,开关样品的下拉电压为34 V～40 V,下拉距离为(1.7±0.2)μm,满足设计要求。     

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.     

RF-MEMS Capacitive Switches Fabricated Using Printed Circuit Processing Techniques

This paper presents radio frequency microelectromechanical systems (RF-MEMS) capacitive switches fabricated using printed circuit processing techniques. The key feature of this approach is the use of most commonly used flexible circuit film, Kapton E polyimide film, as the movable switch membrane. The physical dimensions of these switches are in the mesoscale range. For example, electrode area of a typical capacitive shunt switch on coplanar waveguide (CPW) is 2 mmtimes1 mm, respectively. A CPW shunt switch with insertion loss <0.4 dB and isolation >10 dB in the frequency range of 8 to 30 GHz is reported. K-band, Ku-band, and X-band high-isolation CPW shunt switches designed by inductive compensation of the switch down-position capacitance are also presented. Inductance compensation has been implemented by introducing inductive step-in-width junctions in the MEMS switch electrode. The K-band switch provides a maximum isolation value of 54 dB at 18 GHz. For the K-band switch, the insertion loss is less than 0.3-0.4 dB in the frequency range of 1-30 GHz and the isolation values are better than 20 dB in the frequency range of 12 to 30 GHz. The Ku-band switch provides a maximum isolation of 46 dB at 16.5 GHz. For the Ku-band switch, the insertion loss is less than 0.4-0.45 dB in the frequency range of 1-30 GHz and the isolation is greater than 20 dB in the frequency range of 12 to 22 GHz. The X-band switch provides a maximum isolation value of 32 dB at 10.6 GHz. The insertion loss is less than 0.25-0.3 dB in the frequency range of 1-18 GHz and the isolation is better than 20 dB in the frequency range of 8.5 to 13.5 GHz for the X-band switch. The measured typical pull-down voltage is in the range of 100-120 for this type of switches. These switches are uniquely suitable for monolithic integration with printed circuits and antennas on organic laminate substrates     

Development of a low stress RF MEMS double-cantilever shunt capacitive switch

Microsystem Technologies - In this paper, a novel RF MEMS shunt capacitive switch with application in the Ka frequency band is proposed. The spring design and the step structure added to the beam...