V-shaped micromechanical tunable capacitors for RF applications

A new MEM varactor design is presented. It relies on the displacement of an isolated conductor in the air gap of a V-shaped capacitor. To estimate capacitance and tuning ratio of this structure the distributed point source method (DPSM) has been used for electrostatic simulations. The realisation and characterisation of glass motionless prototypes show the feasibility and the interest of this new concept for RF applications. To obtain actuated mobile devices, a novel silicon process has also been developed.     

A new design for rotational, tunable wideband RF MEMS capacitors

Wide range tunable components are a key point for high frequency performances. We have developed a novel RF MEMS rotational capacitor based on surface variation and high displacement. This paper will present multiple designs with physical parameter variations for comparative test with fabricated device measurements. The goal of this work is to prove the proper operation of the devices according to fulfill target performances. The main parameters will be tunability, capacitance value, resonance frequency and finally maximal actuation voltage allowed.     

Design and modeling of a continuously variable piezoelectric RF MEMS switch

A structure for a piezoelectrically actuated capacitive RF MEMS switch that is continuously variable between the ON state and the OFF state has been proposed. The device is based on variable capacitance using a cantilever fixed at both ends that is actuated using a lead zirconate titanate thin film. Because the device is contactless, the reliability issues common in contact-type RF MEMS switches can be avoided. A comprehensive mathematical model has been developed in order to study the performance of the device, and allow for design optimization. Electrical measurements on test structures have been compared with the performance predicted by the model, and the results used to design a prototype RF MEMS switch. The model and simulations indicate the proposed switch structure can provide an insertion loss better than 0.7 dB and an isolation of more than 10 dB between 6 and 14 GHz with an actuation voltage of 22.4 V. The state of the device is continuously variable between the ON state and the OFF state, with a tunable range of capacitance of more than 15\(\times \).     

High current handling capacity multilayer inductors for RF and microwave circuits

We present test data for several spiral inductors with improved quality factor fabricated on GaAs substrates using the ITT MSAG (multifunction self aligned gate) multilayer process. It is shown experimentally that the quality factor of spiral inductors can be enhanced by using thick metallization and placing inductors on a thick polyimide layer which is placed on top of the GaAs substrate. Using this technique we observed up to 68% improvement in the quality factor of spiral inductors as compared to standard spiral inductors. Inductors having thick metallization can also handle DC currents as large as 0.5 A. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 139–146, 2000.     

Design of MEMS switch for RF applications

Components like passive electronically scanned (sub) arrays, T/R modules, reconfigurable antennas etc., in RF applications are in need of MEMS switches for its re-configurability and polarization. This paper presents the analysis, design and simulation of a MEMS switch. The switch proposed in this paper is intended to work in the frequency range of 4–8 GHz. The proposed switch fulfills the switching characteristics concerning the five requirements loss, linearity, high switching speed, small size/power consumption, low pull down voltage following a relatively simple design, which ensures reliability, robustness and high fabrication yield. The switch implemented in this paper is based on the integration mode of operation and widely used in RF applications.     

Fabrication uncertainties and yield optimization in MEMS tunable capacitors

Intrinsic uncertainties of MEMS fabrication processes can severely affect the performance of devices because the tolerance ranges of these processes are relatively large and improvement of process accuracy is very expensive. Therefore, the analysis of fabrication uncertainties and their outcome on a device performance is a vital task before finalizing the design. In this paper, the effects of process inaccuracy on the performance of MEMS tunable capacitors are studied. Design parameters such as dimensions of electrodes and the initial gap between them and the stiffness of supporting beams are considered as random variables. The variation of these parameters within tolerance ranges drastically alters the capacitor's actual response from the desired one and results in low yield. Hence, design optimization with the objective of maximizing yield in early steps becomes very important. An effective method for yield optimization of MEMS capacitors under given fabrication uncertainties is introduced. The method utilizes aspects of the advanced first-order second-moment (AFOSM) reliability method to find a linearized feasible region to estimate the yield. The yield is calculated directly using the joint cumulative distribution function (CDF) over the tolerance box requiring no numerical integration and avoiding computational complexity. The optimal design verified by Monte-Carlo (M-C) simulation exhibits a significant increase in the yield. The main advantage of this method comparing to other design optimization methods is that the proposed method does not change the design topology or fabrication accuracy. It increases the yield by finding the optimum design variables as demonstrated in this paper.     

Stiction issues and actuation of RF LIGA-MEMS variable capacitors

High aspect ratio variable capacitors have been fabricated using deep X-ray lithography and electroplating. Stiction phenomena applicable to high aspect ratio devices are presented, including the conditions for stiction to occur and the critical dimensions of structures. Actuation tests at 3 GHz are also presented and show a maximum capacitance of 0.86 pF with no actuation voltage and a minimum capacitance of 0.70 pF with an actuation voltage of 20 V just before pull-in, which gives a tuning range of 1.23:1. Corresponding Q-factor values are 49.3 and 70.8 respectively. After pull-in, the measured capacitance is 0.61 pF, corresponding to a tuning range of 1.41:1, with a maximum Q-factor of 102.9.     

一种非接触式微加速度开关的研究

典型的微加速度开关至少包含一个电接触,当阈值加速度值达到时,该开关将闭合。一般为金属接触,比如金。但金属接触可能存在许多问题,如微焊接、电弧、氧化,这些问题可能导致开关工作失灵。鉴于此,本文介绍了一种低驱动电压的非接触式微加速度开关(阈值为5gn)的设计理论、研究方法和主要加工工艺步骤,同时对非接触式微加速度开关结构的力电耦合进行理论计算,结合ANSYS软件仿真分析验证。     

Chip-level integration of RF MEMS on-chip inductors using UV-LIGA technique

This paper presents a chip-level integration of radio-frequency (RF) microelectromechanical systems (MEMS) air-suspended circular spiral on-chip inductors onto MOSIS RF circuit chips of LNA and VCO using a multi-layer UV-LIGA technique including SU-8 UV lithography and copper electroplating. A high frequency simulation package, HFSS, was used to determine the layout of MEMS on-chip inductors with inductance values close to the target inductance values required for the RF circuit chips within the range of 10%. All MEMS on-chip inductors were successfully fabricated using a contrast enhancement method for 50 μm air suspension without any physical deformations. High frequency measurement and modeling of the integrated inductors revealed relatively high quality factors over 10 and self-resonant frequencies more than 15 GHz for a 1.44 nH source inductor and a 3.14 nH drain inductor on low resistivity silicon substrates (0.014 Ω cm). The post-IC integration of RF MEMS on-chip inductors onto RF circuit chips at a chip scale using a multi-layer UV-LIGA technique along with high frequency measurement and modeling demonstrated in this work will open up new avenues with the wider integration feasibility of MEMS on-chip inductors in RF applications for cost-effective prototype applications in small laboratories and businesses.     

一种RF MEM电感及其LC低通滤波器的模拟和设计

模拟并设计了一种基于表面微机械加工的平面MEM电感,提出了它的等效电路模型并给出模型中参数的提取方法。由模拟结果验证了该等效电路具有较高的精度,误差在8%以内。设计的一个3.6nH的平面MEM电感的品质因数超过20,自谐振频率超过15GHz。由平面MEM电感构成的5阶LC低通滤波器的-3dB带宽为3.7GHz,0~3GHz内的插入损耗低于1dB。     

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。     

Effect of filter parameters on the phase noise of RF MEMS tunable filters employing shunt capacitive switches

The effect of filter parameters on the phase noise of RF MEMS tunable filters employing shunt capacitive switches is investigated in this article. It is shown that the phase noise of a tunable filter is dependent on the input power, fractional bandwidth, filter order, resonator quality factor, and tuning state. Phase noise is higher for filters with smaller fractional bandwidth. In filters with high fractional bandwidth (>3%), phase noise increases as the input power approaches the power‐handling capability of the filter. In filters with smaller bandwidths, phase noise increases with input power upto a threshold level of input power, but begins to decrease thereafter. The unloaded quality factor of the filter has a noticeable effect on the phase noise of filters with narrow bandwidths. The phase noise changes with the filter tuning state and is maximum when all the switches are in the up‐state position. It is also shown that the phase noise increases with the filter order, due to increase in the number of noisy elements in the filter structure. This article provides a methodology to evaluate the phase noise of a tunable filter and proves that RF MEMS filters are suitable for high performance applications without considerable phase‐noise penalty. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

声光可调谐滤光器的原理与应用

本文介绍了声光可调谐滤光器(AOTF)的工作原理和基于AOTF的光谱分析仪器的基本构造、特点,以及AOTF光谱分析仪器的发展应用情况.     

Multiport RF MEMS switch for satellite payload applications

Microsystem Technologies - Design, fabrication and characterization of a novel RF switch is proposed in this paper. The multiport RF MEMS switch provides a single input multiple output novel...     

Scalable lumped modeling of single‐ended and differential inductors for RF IC design

A lumped scalable model of silicon integrated inductors for RF IC design is presented. It was validated up to 20 GHz using measured performance parameters of more than 70 single‐ended and differentially driven spirals covering 0.2‐ to 8.3 nH inductance values. Excellent accuracy, full geometrical scalability, compactness and high capability for implementation in circuit simulators promote the proposed model as a reliable time‐saving design tool. Two circuital example, i.e., 5‐GHz down‐converter and 10‐GHz VCO, are also presented to demonstrate its use in practical cases. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

MEMS tunable capacitors with fragmented electrodes and rotational electro-thermal drive

This paper reports on the design, simulation and fabrication of tunable MEMS capacitors with fragmented metal (AlSi 4%) electrodes. We examine a rotational electro-thermal actuation. An analytic model of the rotational effect thermal actuator was established in order to show the periodicity of the capacitance when the angle increases. Evaluation of the impact of fringing fields on the capacitance has been carried out using finite element analysis (FEA). The MEMS capacitors were fabricated using metal surface micromachining with polyimide sacrificial layer. The maximum rotation, corresponding to a maximum angle of 7°, was obtained near 1.2 V and 299 mA. The proposed capacitor has a practical tuning range of 30%. FEA has shown that this figure can be improved with design optimization. The MEMS architecture based on rotational effect and fragmented electrodes does not suffer from the pull in effect and offers a practical solution for future above-IC capacitors.     

发展中的RF MEMS开关技术

从驱动方式和机械结构的角度介绍了不同的RF MEMS开关类型,分析了各类MEMS开关的性能及优缺点,分析了MEMS开关在制作和发展中面临的牺牲层技术、封装技术、可靠性问题等关键技术和问题,介绍了MEMS开关的发展现状及其在组件级和系统级的应用,以及对MEMS开关技术的展望。     

Design of wide range MEMS tunable capacitor for RF applications

The RF applications like voltage controlled oscillators, tunable filters, resonators etc., requires tunable capacitors in their designs. This paper presents the design of wide range MEMS tunable capacitors for RF applications. This design consists of an air suspended bottom plate and a fixed top plate. The top fixed plate and the suspended bottom plate form the tunable capacitor. The capacitance range of this tunable capacitor is from 69.172 to 138.344?nF. This range is wider compared with the conventional MEMS tunable capacitors of tuning ranges in pico Farads. The fabrication process is similar to that of the existing standard integrated circuit fabrication processes, which makes this design suitable for integrated RF applications.     

Design of active inductors in SiGe/SiGe:C processes for RF applications

Applicability of silicon‐based heterojunction bipolar processes is investigated for designing active inductors with high quality factors (Q). Results for grounded type one‐port active inductor incorporating frequency‐dependent as well as frequency‐independent negative resistances are examined. Later, the negative resistance aspect is extended from one‐port to two‐port active inductor circuit to ensure its use as a series element. The enhanced Q‐values of all the inductive circuits are observed in accordance with the theory. Moderately high‐Q values (～100) with considerable inductances (～0.2–1 nH) are obtained in the RF frequency ranges (～5–9 GHz). © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Design and analysis of RF MEMS shunt switch for V-band applications

Microsystem Technologies - In this paper, we have designed and simulations of RF MEMS shunt switch. The electro-mechanical and electromagnetic analysis of the switch have been done using COMSOL...