RF MEMS variable attenuators with improved dB-linearity

Microsystem Technologies - A variable attenuator is one of the essential components in radio frequency (RF) systems, such as automatic gain control amplifiers and full-duplex systems. Variable...     

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\(\times \).     

Germanium resistors for RF MEMS based microsystems

This paper introduces the use of germanium as resistive material in RF MicroElectroMechanical (MEMS) devices. Integrated resistors are indeed highly required into RF MEMS components, in order to prevent any RF signal leakage in the bias lines and also to be compatible with ICs. Germanium material presents strong advantages compared to others. It is widely used in microtechnologies, notably as an important semi-conductor in SiGe transistors as well as sacrificial or structural layers and also mask layer in various processes (Si micromachining especially). But it also presents a very high resistivity value. This property is particularly interesting in the elaboration of integrated resistors for RF components, as it assures miniaturized resistors in total agreement with electromagnetic requirements. Its compatibility as resistive material in MEMS has been carried out. Its integration in an entire MEMS process has been fruitfully achieved and led to the successful demonstration and validation of integrated Ge resistors into serial RF MEMS variable capacitors or switches, without any RF perturbations.     

Deep neural network watermarking based on a reversible image hiding network

Pattern Analysis and Applications - Recently, many researchers have proposed deep neural network (DNN) watermarking technologies, DNN watermarking approaches can be divided into two categories:...     

Fabrication of RF MEMS variable capacitors by deep X-ray lithography and electroplating

Radio frequency micro electro-mechanical systems (RF MEMS) vertical cantilever variable capacitors fabricated using deep X-ray lithography and electroplating are presented. Polymethylmethacrylate (PMMA) layers of 100 μm and 150 μm have been patterned and electroplated with 70 μm and 100 μm thick nickel. A 3 μm thick titanium layer was used as plating base as well as etch time-controlled sacrificial layer for the release of the cantilever beam. The parallel plate layout includes narrow gaps and cantilever beams with an aspect ratio in nickel of up to 60 for 1 mm long features. Auxiliary structures support the beams and gaps during the processing. Room temperature electroplating significantly reduces the risk of deformations compared to the standard process temperature of 52°C. The capacitors operate in the 1–5 GHz range, and demonstrate good RF performance, with quality factors on the order of 170 at 1 GHz for a 1 pF capacitance.     

Novel high capacitance ratio compact float metal based RF MEMS switch for multi band and variable bandwidth: design and RF performance analysis

Microsystem Technologies - Modern complex systems, as they are multi functional, they require many small unit cells for multi functionality. These are certain applications, where the change in...     

Towards a continuous microfluidic rheometer

In a previous paper we presented a way to measure the rheological properties of complex fluids on a microfluidic chip (Guillot et al., Langmuir 22:6438, 2006). The principle of our method is to use parallel flows between two immiscible fluids as a pressure sensor. In fact, in a such flow, both fluids flow side by side and the size occupied by each fluid stream depends only on both flow rates and on both viscosities. We use this property to measure the viscosity of one fluid knowing the viscosity of the other one, both flow rates and the relative size of both streams in a cross-section. We showed that using a less viscous fluid as a reference fluid allows to define a mean shear rate with a low standard deviation in the other fluid. This method allows us to measure the flow curve of a fluid with less than 250 μL of fluid. In this paper we implement this principle in a fully automated set up which controls the flow rate, analyzes the picture and calculates the mean shear rate and the viscosity of the studied fluid. We present results obtained for Newtonian fluids and complex fluids using this set up and we compare our data with cone and plate rheometer measurements. By adding a mixing stage in the fluidic network we show how this set up can be used to characterize in a continuous way the evolution of the rheological properties as a function of the formulation composition. We illustrate this by measuring the rheological curve of four formulations of polyethylene oxide solution with only 1.3 mL of concentrated polyethylene oxide solution. This method could be very useful in screening processes where the viscosity range and the behavior of the fluid to an applied stress must be evaluated.     

Analytical design of MEMS variable capacitors based on shaped-finger comb-drives

Microsystem Technologies - A variable capacitor is one of the widely used components in radio frequency (RF) circuits. Variable capacitors can benefit from the microelectromechanical systems (MEMS)...     

On the tunability of a MEMS based variable capacitor with a novel structure

In this work a novel MEMS based variable capacitor has been presented. To increase the tunability and decrease the applied voltage, the conventional fixed-fixed beam used in CPW lines has been changed to a fixed-simple supported beam. The proposed structure is a simple cantilever micro-beam in the first step of deflection and is changed to a fixed-simple supported micro-beam in the second step of motion. In the capacitive micro-structures increasing the applied voltage decreases the equivalent stiffness of the structure and leads the system to an unstable condition by undergoing to a saddle node bifurcation. In the proposed structure to avoid pull-in instability and increase the capacitance tuning range, mechanical stiffness of the structure is increased by changing boundary conditions by locating a pedestal in the end of the cantilever beam. The governing nonlinear equation for static deflection of the micro-beam, based on Euler–Bernoulli micro-beam theory has been presented. The results show that the proposed structure increases the capacitance tuning range and decreases the applied voltage. The results also show that the position of the pedestal affects the tunability and the threshold voltage of the structure.     

Modeling and optimization of a solenoidal integrated inductor for RF ICs

A solenoidal structure for implementation of on‐chip inductors is presented. An electromagnetic simulator is used to simulate several different‐size inductors for up to 20 GHz. Additionally, artificial neural network models are developed for different inductor topologies to speed up inductors optimization process. Finally, it is demonstrated that the solenoidal inductor exhibits a better overall performance in comparison to the conventional multilayer spiral inductors demonstrating its potential for RF ICs. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Electrothermally Actuated RF MEMS Switches Suspended on a Low-Resistivity Substrate

This paper presents an electrothermally actuated lateral resistive-contact switch for application to low-gigahertz-band communication systems. It was manufactured on a standard low-resistivity substrate, and its RF performance was improved by suspending the structures 25 mum from the substrate, which is a strategy for future integration with active devices in the system-on-chip concept. Measured insertion losses are -0.26 dB at 1 GHz and -0.65 dB at 6 GHz, return losses are -29 dB at 1 GHz and -25 dB at 6 GHz, and isolations are -52 dB at 1 GHz and -26 dB at 6 GHz. The device is driven by a metal electrothermal actuator, which achieves large displacements and contact forces at much lower temperatures than traditional polysilicon electrothermal actuators. The RF power handling characteristics are also addressed and measured.     

基于PSO-BP神经网络的MEMS加速度计温度补偿

针对扭摆式硅微加速度计的温漂问题,在对比分析不同算法补偿效果的基础上,提出了基于自适应权重粒子群优化(PSO)算法优化反向传播(BP)神经网络温度补偿方法,同时借鉴传统遗传算法中的变异思想,在PSO算法中引入变异操作,克服了BP神经网络易陷入局部极值缺陷,且温度补偿精度相对其他算法更具有全局性,达到了高精度实时温度补偿效果。测试结果表明:补偿后的标度因数温度系数、全温零偏极差和非线性分别由141×10~(-6)/℃,109. 111 mgn和2223×10~(-6)减小为13. 22×10~(-6)/℃,9. 941 mgn和294×10~(-6),验证了提出方法的优越性和实用性。     

Design of a novel RF MEMS square resonator

A novel kind of RF MEMS square resonator with a movable electrode structure that is driven by electrostatic force is proposed. Within the scope of the fabrication process allowed, the gap between the movable electrode and resonance square is decreased from 2.5 to 0.5 μm, which greatly reduces motional resistance so that resonator is easier to resonate. Then the DC driving voltage that makes electrode move setting displacement is deduced theoretically. The finite element simulation and analysis software ANSYS are used to validate mechanical vibration modal and determine center frequency of resonator. In addition, simulation of harmonic analysis is applied to obtain the change of output current and motional resistance before and after the electrode moving. Moreover, the design can also, to a certain extent, ease the difficulty of manufacturing the small gap in the micro-processing technology.     

A comprehensive study on RF MEMS switch

This paper emphasis on state-of-the-art of the earlier until the current trend and demand, principles, design considerations, key performance and fabrication technology of RF MEMS switch devices developed over the past few years. RF MEMS switch performance and features such as actuation voltage, insertion loss, isolation and ease with cost of fabrication and applications are compared and discussed.     

一种平板式MEMSRF射频开关的设计

介绍了一种实用的平板电容式MEMSRF射频开关。研究了外加驱动电压与由此所引起的极板间距和极板受力变化之间的非线性关系,提出了一种有效的基于有限元的设计分析方法,在此基础上设计了相应的MEMS加工工艺流程,并给出了具体的MEMS工艺。     

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.

     

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。     

Design and analysis of a novel MEMS spiral inductor with high quality factor

Microsystem Technologies - In this paper a novel spiral inductor with high quality (Q)-factor is presented. Non-uniform current density distribution, especially in inner turn, increases the...     

Effect of residual stress on RF MEMS switch

Studies have been carried out on a RF MEMS shunt switch to analyze the effect of residual stress on its electromechanical characteristics. This paper presents the simulated results as well as theoretically calculated results of a shunt switch due to the presence of residual stress gradient in respect of resonant frequency, pull down voltage and switching characteristics. The effect of introduction of holes in the beam is also studied. The calculated results, corresponding to the switch (without holes) at zero residual stress, of resonant frequency, pull-down voltage and switch on and off time are 28.14 kHz, 28.2 V, 16.35 μsec and 8.6 μsec respectively. Modal analysis of the both the structures (with and without holes) are carried out for different values of residual stress gradients. Modal analysis predicted that higher values of tensile stress gradient are not favorable for switching action. The pull-down voltages and switch on and off times are simulated at different stress gradients. With the increase in compressive stress gradient, the pull-down voltage is found to increase, whereas, switch on and off times is decreased. Corresponding to −20 MPa/μm residual stress gradient, the resonant frequency, pull-down voltage and switch on and off times are found to be 74.5 kHz, 63.5 V, 7.5 μsec and 3.36 μsec respectively. Introduction holes in the structure modified these values to 63.77 kHz, 53.1 V, 8.7 μsec, 3.92 μsec respectively.