A double microbeam MEMS ohmic switch for RF-applications with low actuation voltage (original) (raw)
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MEMS SPDT microswitch with low actuation voltage for RF applications
Microelectronics International, 2015
In the present work, we propose a novel design of an ohmic contact SPDT (Single-Pole Double-Throw) MEMS microswitch for RF applications. We study the dynamic behavior of the SPDT MEMS microswitch. The proposed microswitch (SPDT design) shares antenna between transmitter and receiver in a wireless sensor. An electrical voltage is used to create an electrostatic force that controls the On/Off states of the microswitch. First, we develop a mathematical model of the proposed microswitch and propose a Reduced-Order Model (ROM) of the design, based on the Differential Quadrature Method (DQM), which fully incorporates the electrostatic force nonlinearities. We solve the static, transient and dynamic behavior and compare the results with Finite Element solutions. Then we examine the dynamic solution of the switch under different actuation waveforms. The obtained results showed a significant reduction in actuation voltage, pull-in bandwidth and switching time.
Journal of Micromechanics and Microengineering, 2007
In this paper we present a 3D nonlinear dynamic model which describes the transient mechanical analysis of an ohmic contact RF MEMS switch, using finite element analysis in combination with the finite difference method. The model includes real switch geometry, electrostatic actuation, the two-dimensional non-uniform squeeze-film damping effect, the adherence force, and a nonlinear spring to model the interaction between the contact tip and the drain. The ambient gas in the package is assumed to act as an ideal and isothermal fluid which is modeled using the Reynolds squeeze-film equation which includes compressibility and slip flow. A nonlinear contact model has been used for modeling contact between the microswitch tip and the drain electrode during loading. The Johnson-Kendall-Roberts (JKR) contact model is utilized to calculate the adherence force during unloading. The developed model has been used to simulate the overall dynamic behavior of the MEMS switches including the switching speed, impact force and contact bounce as influenced by actuation voltage, damping, materials properties and geometry. Meanwhile, based on a simple undamped spring-mass system, a dual voltage-pulse actuation scheme, consisting of actuation voltage (V a ), actuation time (t a ), holding voltage (V h ) and turn-on time (t on ), has been developed to improve the dynamic response of the microswitch. It is shown that the bouncing of the switch after initial contact can be eliminated and the impact force during contact can be minimized while maintaining a fast close time by using this open-loop control approach. It is also found that the dynamics of the switch are sensitive to the variations of the shape of the dual pulse scheme. This result suggests that this method may not be as effective as expected if the switch parameters such as threshold voltage, fundamental frequencies, etc. deviate too much from the design parameters. However, it is shown that the dynamic performance may be improved by increasing the damping force. The simulation results obtained from this dynamic model are confirmed by experimental measurement of the RF MEMS switches which were developed at the Northeastern University. It is anticipated that the simulation method can serve as a design tool for dynamic optimization of the microswitch. In addition, the approach of tailoring actuation voltage and the utilization of squeeze-film damping may provide further improvements in the operation of RF MEMS switches.
Dynamic Study of a Capacitive MEMS Switch with Double Clamped-Clamped Microbeams
Shock and Vibration, 2014
We study a capacitive MEMS switch composed of two clamped-clamped exible microbeams. We first develop a mathematical model for the MEMS switch where the upper microbeam represents the ground transmission line and the lower one represents the central transmission line. An electrostatic force is applied between the two microbeams to yield the switch to its ON and OFF states. We derive the equations of motion of the system and associated boundary conditions and solve the static and dynamic problems using the differential quadratic method. We show that using only nine grid points gives relatively accurate results when compared to those obtained using FEM. We also examine the transient behavior of the microswitch and obtain results indicating that subsequent reduction in actuation voltage, switching time, and power consumption are expected along with relatively good RF performances. ANSYS HFSS simulator is used in this paper to extract the RF characteristics of the microswitch. HFSS simulation results show that the insertion loss is as low as −0.31 dB and that the return loss is better than −12.41 dB at 10 GHz in the ON state. At the OFF state, the isolation is lower than −23 dB in the range of 10 to 50 GHz.
IEEE Transactions on Microwave Theory and Techniques, 2005
This paper reports new RF microelectromechanical systems (MEMS) switches actuated by the combination of electromagnetic and electrostatic forces for low-voltage and low-power operation. The proposed RF MEMS switches have utilized the proper combination of two actuation mechanisms: taking advantage of the large actuation force from electromagnetic actuation for initial movement and the low-power feature from electrostatic actuation for holding the actuator position. Both series-and shunt-type switches have been implemented using the proposed actuation mechanism. From the fabricated switches, feasibility of operation has been successfully demonstrated. The fabricated switches can be operated within several hundred microseconds. In the series-type switch, the isolation has been measured as 34 dB and insertion loss as 0.37 dB at 20 GHz. In the shunt type switch, the isolation is 20.7 dB and insertion loss is 0.85 dB at 19.5 GHz. The proposed RF MEMS switches are mechanically robust and the combination of electromagnetic and electrostatic actuations makes it possible to achieve excellent switching characteristics at low power and low voltage below 5 V.
Design and Simulation of Micro-Switches for RF Applications
Ijca Proceedings on International Conference and Workshop on Emerging Trends in Technology 2013, 2013
The acronym MEMS is used almost universally to refer to all devices that are produced by micro fabrication or micromachining except integrated circuit (IC). Micro machining is any process that deposits, etches, or defines materials with minimum features measured in micrometers or less. Micro-switches are essentially micro-cantilevers that are fixed at both ends. They are mainly used in MEMS applications such as filters and switches. The main stiffness of a fixed-fixed constant rectangular cross-section is the one relating to z-translation (bending about the y-axis) and is formulated at the midpoint of the switch.The work presented in this paper involves design and simulation of MEMS switches.The devices consist of different dimensions microswitches varying length from 300um to 500um with three different widths (20um to 40um).The work focuses on the realization of electrostatic low actuation switches with main emphasis on the pull-in voltage and RF response.
Electromechanical considerations in developing low-voltage RF MEMS switches
IEEE Transactions on Microwave Theory and Techniques, 2003
This paper reports on the design, fabrication, and testing of a low-actuation voltage Microelectromechanical systems (MEMS) switch for high-frequency applications. The mechanical design of low spring-constant folded-suspension beams is presented first, and switches using these beams are demonstrated with measured actuation voltages of as low as 6 V. Furthermore, common nonidealities such as residual in-plane and gradient stress, as well as down-state stiction problems are addressed, and possible solutions are discussed. Finally, both experimental and theoretical data for the dynamic behavior of these devices are presented. The results of this paper clearly underline the need of an integrated design approach for the development of ultra low-voltage RF MEMS switches.
2013
This paper proposes a novel RF MEMS dc-contact switch with stiff membrane on a quartz substrate. The uniqueness of this work lies in the utilization of a seesaw mechanism to restore the movable part to its rest position. The switching action is done by using separate pull-down and pull-up electrodes, and hence operation of the switch does not rely on the elastic recovery force of the membrane. One of the main problems faced by electrostatically actuated MEMS switches is the high operational voltages, which results from bending of the membrane, due to internal stress gradient. This is resolved by using a stiff and thick membrane. This membrane consists of flexible meanders, for easy movement between the two states. The device operates with an actuation voltage of 6.43 V, an insertion loss of -0.047 dB and isolation of -51.82 dB at 2 GHz.
Design and Analysis of a Radio Frequency Based Non-Contact Type Micro Electromechanical Switch
2022 International Conference on Emerging Trends in Smart Technologies (ICETST), 2022
Microelectromechanical switches are mostly used in cellular communication systems. These are reliable as compared to other semiconductor switches which include high resolution, small size, low power consumption and cost. Radio frequency microelectromechanical systems (RF-MEMS) based switches usually fabricate through electrothermal, electrostatic and piezoelectric actuation methods. In this paper, design and analysis of three state non-contact type RF-MEMS switch have been presented. The designed switch is free from micro-welding issues and a static fraction that occurs commonly in contact types of microsystem switches. The switch operation principle depends on the change in capacitance between ground lines and signal lines. The capacitance is adjusted by the electrostatic actuation mechanism. The freely movable ground lines work bidirectionally therefore switching can be achieved between OFF, ON, and deep OFF states. The low actuation voltage is obtained by designing a flexible spring and increasing the overlap area of actuation electrodes.
A New Electrostatically Actuated Low Voltage RF Mems Switch
European Scientific Journal, 2013
This paper describes the design and simulation of a new low voltage electrostatically actuated RF MEMS switch. The switch structure is designed in such a way that, the inherent limitation of electrostatic actuation is relaxed and the actuation voltage is as low as 3.5 V. The idea is to using a two-step electrostatic actuation mechanism instead of conventional two parallel plate electrostatic actuators. In fact the gap between switch and transmission line is reduced in two steps. In order to investigate the usefulness of the proposed idea, both mechanically and electromagnetically, FEM simulations are carried out and satisfactory results are obtained. The RF characteristics of the switch are as follow; Isolation -12 dB at 30 GHz, Insertion Loss -0.08dB at 30 GHz and return loss was below -20 dB at 30 GHz. The proposed switch in this paper can be a promising choice for low voltage high performance RF MEMS switches.
Role of the electro-thermo-mechanical multiple coupling on the operation of RF-microswitch
Microsystem Technologies, 2012
A phenomenological approach is proposed to identify some effects occurring within the structure of the microswitch conceived for radio frequency application. This microsystem is operated via a nonlinear electromechanical action imposed by the applied voltage. Unfortunately, it can be affected by residual stress, due to the microfabrication process, therefore axial and flexural behaviors are strongly coupled. This coupling increases the actuation voltage required to achieve the so-called ''pull-in'' condition. Moreover, temperature may strongly affect strain and stress distributions, respectively. Environmental temperature, internal dissipation of material, thermo-elastic and Joule effects play different roles on the microswitch flexural displacement. Sometimes buckling phenomenon evenly occurs. Literature show that all those issues make difficult an effective computation of ''pull-in'' and ''pull-out'' voltages or evenly distinguishing the origin of some failures detected in operation. Analysis, numerical methods and experiments are applied to an industrial test case to investigate step by step the RF-microswitch operation. Multiple electro-thermo-mechanical coupling is first modeled to have a preliminary and comprehensive description of the microswitch behavior and of its reliability. ''Pull-in'' and ''pull-out'' tests are then performed to validate the proposed models and to find suitable criteria to design the RF-MEMS.