Y-Shaped Cantilever Beam RF MEMS Switch for Lower the Actuation Voltage

Microwave switches are extensively used in many wireless and satellite communication systems. They are mainly used for signal routings and reconfigurations. Recently, due to the development of micro-mechanical systems (MEMS), RF MEMS switches are being widely investigated. Although RF MEMS switches have been intensively studied, limited work was done on switches that are suitable for integration in large switching networks such as switch matrices and multi-bit phase shifters [1, 2]. These switching networks require very small switches each with independent controls. Their major existing problems are the high actuation voltage and the low switch yield. High actuation voltage is undesired as a more complicated circuitry is required to provide suitable control signal. Low yield is another drawback as it could result in malfunctioning of some of the switches and thus the entire integrated system. One of the major contributions in resulting of low yield in RF MEMS switches are their dependency to the residual stress of the fabrication process both across one wafer and across batches. This problem is much more pronounced on switches with long length as they deform to their curled shape and prevent switching. In this paper, a novel type of switch is proposed that could reduce the stress sensitivity of the switch as well as providing a low actuation voltage. The overall switch structure is design with size miniaturization.

This paper presents the design optimization and simulation of low-voltage series and capacitive radio frequency (RF) Micro-electromechanical (MEMS) switches using ANSYS Multiphysics. First, a series switch is simulated using shape memory alloy (SMA) which shows that the use of SMA beam to actuate switching, allows the excitation voltage to be relatively much lower (5 V) compared to that needed for electrostatic actuation (30 V). Secondly, in the capacitive switch structure both contact plates of the switch are designed as displaceable membranes with similar dimensions and conditions, differing on only membrane materials. The obtained results (5 V) indicate about 30% reductions in actuation voltage from the conventional single beam (15 V). The stress on the beam due to the actuation voltage is also reduced increasing the switching life time.

Triggers for high voltage (HV) switches have always been critical components for reliable, efficient pulsed power systems because they control the timing synchronization and amplitude variation of multiple pulse forming lines that combine to produce the total system output pulse. In pulsed power systems of the future, the role of trigger systems are even more critical as they trigger more components and produce shaped-pulses by independent timing of individual switches or switch groups. Conventional trigger systems require high voltage trigger cables or line-of-sight optics that complicate design, demand space, and require extensive maintenance. With electrical triggers, large diameter, high voltage transmission line cables must be fed through high field regions. With optical triggers, line-of-sight optics must focus high energy laser beams to the interior of the switches with clean, rigidly-mounted, shock- withstanding optics. This paper reports on efforts to develop fiber- optically triggered photoconductive semiconductor switches (PCSS) to trigger high voltage switches with improved precision and eliminate the need for large- diameter trigger cables or line-of-sight optics. These triggers simplify design because their optical-isolation allows them to "float" with the switches that they trigger and have truly independent EMP-free timing control over 200 micron diameter optical fibers. They improve the performance of prime power switches, diverters, and diagnostics because their low-jitter sub-nanosecond rise times are more precise and more easily adjusted than conventional trigger sources. For pulse charged switches, the PCSS triggers can generally derive their trigger energy from the stray fields of the high voltage switch. Test results will be presented that have demonstrated 100 ps r-m-s jitter from a 40 kV, 500 ps rise time, PCSS- triggered 300 kV trigatron gas gap. PCSS design requirements, switching properties, and trade-offs for building high voltage trigger systems will also be described based on many previous experiments with PCSS technology. Results from PCSS Blumlein and PCSS capacitive discharge pulsers will be discussed along with the designs to use these pulsers to trigger both DC and pulse charged high voltage switches.

We report the first ever silicon carbide (SiC) nano-electro-mechanical systems (NEMS) switches capable of operation from 25 to 600degC. We have developed both laterally- and vertically-actuated designs with threshold voltages of less than 5 V. Switches have been verified to cycle more than 3 billion times at room temperature and more than 2 million times at 600degC. Plausible models to describe the contact resistance in two actuation voltage regimes are also suggested: (i) at low actuation voltage, the resistance is dominated by the native oxide which forms on the SiC surface; and (ii) at higher actuation voltages, the resistance can be described by Sharvin's model.

This paper presents the analytical and experimental results on optimal placement of piezoceramic actuators for shape control of beam structures. The objective is to determine the optimum piezoceramic actuator locations and voltages to minimize the error between the desired shape and the achieved shape. The analytical model for predicting beam deformation due to a piezoelectric actuator is based on the Euler-Bernoulli model. The cost function has fifth-order polynomials in the actuator locations and second-order polynomials in actuator voltages. This difference resulted in difficulty in simultaneous optimization of actuator locations and voltages. Using embedded Nader and Mead simplex algorithms to separately optimize actuator locations and voltages was found to produce reliable results, converging to the same optimum solution for a variety of initial conditions. Experimental results show that the analytical model provides a reasonable prediction of actuator performance at low input voltage, but does not account for the nonlinear behavior of the piezoceramic and effects of hysteresis.

Capacitive RF MEMS switches present several drawbacks such as high actuation voltages, slow switching times and time-varying performances, due to the deterioration of both their mechanical and electrical properties. Such characteristics justify the interest of the scientific community on the development of accurate measurement techniques to monitor the dynamic behavior of capacitive MEMS switches during continuous actuations. In this paper, a novel measurement system devoted to the time-domain characterization of capacitive MEMS switches is proposed. Moreover, an electrical model for such devices is introduced and its lumped elements are characterized by means of measurement results. The proposed test-bench allows to measure the modulus and the phase of both the incident and the reflected signals of a one-port transmission line based, where the port is represented by the capacitive MEMS device. The paper introduces a software tool based on LabVIEWtrade to compute the capacitance and the resistance values of the model as functions of time. In particular the tool transforms the measured signals in the frequency domain to compute the reflection coefficient by means of components depending on the fundamental frequency of the RF signal, thus neglecting spurious frequency components, out-band noise and harmonics due to interferences

This paper presents high cycle fatigue properties of an Al-3%Ti thin film, used in a RF (radio-frequency) MEMS switch for a mobile phone. The thickness and width of the thin film of specimen are 1.1 μm and 480 μm, respectively. Tensile tests of five specimens are performed, from which the ultimate strength is found to be 144MPa. High cycle fatigue tests of six specimens are also performed, from which the fatigue strength coefficient and the fatigue strength exponent are found to be 336MPa and −0.1514, respectively.

Radio frequency (RF) MEMS is an emerging sub-area of MEMS technology that is revolutionizing RF and microwave applications. RF MEMS devices have a broad range of optional applications in military and commercial wireless communication, and navigation and sensor systems. This article presents the EM design of different multiport toggle switches. Such a multiport switch can be used in the compact designs of switching matrices, routing networks, or phase shifters. One application range is the creation of electronically steerable antenna arrays, which can be used for radar applications and satellite communication. The miniaturized switches are based on the single pole single throw (SPST) toggle switch and, in addition to their small size, they have an increased RF performance regarding losses and operation bandwidth (DC to 50 GHz). A 3D FDTD field solver has been used for the electromagnetic design of all the switches. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 329–337, 2004.

This paper presents on an electrostatically actuated microelectromechanical series switch for DC to RF signals, based on a flexible S-shaped film actuator moving between two electrodes in touch mode actuation. This novel concept, in contrast to most other MEMS switches, allows a low actuation voltage design independent on the off-state gap height, which makes larger switching contact areas for low insertion loss and higher current handling capability possible, by obtaining high isolation. Furthermore, the double anchor principle avoids self-biasing and is favorable of switching higher power signals. The actuation voltages of the first prototype switches are 12 V to open and 15.8 V to close the metal contact. The RF isolation with a gap distance of 14.2 /spl mu/m is better than -45 dB up to 2 GHz and -30 dB at 15 GHz despite a large switching contact area of 3500 /spl mu/m/sup 2/.

In this paper, we present the design and fabrication of a large deflection MEMS actuator directly integrated as a variable-ratio radio frequency (RF) power divider in a waveguide. The device is based on a tilting microplate suspended by SU-8 springs and driven by a vertical comb drive actuator. The fabricated device is characterized by laser Doppler vibrometer and white light interferometer measurements. The dynamic measurement confirms the resonance frequency of the torsional mode being around 370 Hz, from which the spring stiffness has been extracted and used for static modeling of the device. The fabricated microplate devices achieved deflection angles of 5.9° with a dc actuation voltage of 30 V. First RF transmission measurements show good agreement with results from electromagnetic field simulations. A variable power split ranging from equal division up to a ratio of more than 1:2 is measured at 82.5 GHz whilst keeping the amount of dissipated power below 25%. This is the first reported actuated RF MEMS device integrated in a metal waveguide operating at such high frequency.

This paper presents the design a capacitive shunt type RF-MEMS switch with high isolation, high switching speed and low actuation voltage for Ka-band applications. The proposed RF-MEMS switch has chosen different structures to reduce the actuation voltage. This paper investigates various analysis such as Electromechanical and RF characteristics of the proposed switch. The beam material taken as the gold and the dielectric is taken as Si3N4 with ℰr as 7.5 and the pull-in voltage of proposed switch obtained as 3.37 V. The proposed different RF-MEMS switches have been analyzed over the range of 26.5–40 GHz frequency. The clamped-clamped structure type RF MEMS Switch is having high isolation as − 46.37 dB at 40 GHz. The perfection of RF losses makes these switches as a good choice for a high frequency of K-band.

Design and Simulation of RF MEMS Switch for X-band Applications

Advanced understanding of the physics makes phase change materials (PCM) and metal-insulator transition (MIT) materials great candidates for direct current (DC) and radio frequency (RF) switching applications. In the literature, germanium telluride (GeTe), a PCM, and vanadium dioxide (VO2), an MIT material have been widely investigated for DC and RF switching applications due to their remarkable contrast in their OFF/ON state resistivity values. In this review, innovations in design, fabrication, and characterization associated with these PCM and MIT material-based RF switches, have been highlighted and critically reviewed from the early stage to the most recent works. We initially report on the growth of PCM and MIT materials and then discuss their DC characteristics. Afterwards, novel design approaches and notable fabrication processes; utilized to improve switching performance; are discussed and reviewed. Finally, a brief vis-á-vis comparison of resistivity, insertion loss, isolation loss, power consumption, RF power handling capability, switching speed, and reliability is provided to compare their performance to radio frequency microelectromechanical systems (RF MEMS) switches; which helps to demonstrate the current state-of-the-art, as well as insight into their potential in future applications.

A vertical RF-MEMS (Radio Frequency Micro ElectroMechanical Switch) switch design is proposed in this work that features a shunt capacitive configuration and can operate at a very low actuation voltage. Besides operating on a low switching voltage, the switch behold a small value of insertion loss in Up (ON) state and offers a towering isolation factor in Down (OFF) state. A horizontal structure of bridge membrane is used in the proposed design and the switch function (with ON and OFF operating states) is provided by the vertical movement of this membrane structure that is controlled by the electrostatic actuation technique. The actuation pad is centrally fed by a Coplanar Waveguide structure. The switch performance has been analysed over a wide frequency range from 1 to 40 GHz. For obtaining a 1.5 μm vertical displacement of the bridge membrane, a sheer 3.0 Volts of pull-in voltage (VPI) is required. CoventorWare and HFSSv13 tools are used in this work for designing and analysing the proposed switch. The use of fixed-fixed flexure beam configuration is chosen for switch design. Simulation results showcase excellent RF characteristics with isolation factor of −47 dB (at 32.5 GHz) and insertion loss in range of −0.01 to −1.10 dB (for 1−40 GHz frequency).

Micro-electro-mechanical-systems(MEMS) switches have low resistive loss, negligible power consumption, good isolation and high power handling capability compared with semiconductor switches. Lifetime of capacitive shunt switches strongly depends on the actuation voltage so low voltage switches is necessary to enhance its performance as well as to broaden its application area. This paper presents the design and simulation of low voltage capacitive shunt MEMS switches together with its RF performance for high frequency applications. The low voltage switches are realized by lowering the spring constant of the beam using serpentine spring designs together with large capacitive area so as to achieve the good RF performance as well. The pull-in voltage is analyzed with commercial CAD finite element analysis software CoventorWare. The electromagnetic performance in terms of scattering parameters, insertion loss, and isolation are analyzed with software Ansoft HFSS10. The switches achieved insertion loss $$<$$ < 0.47 dB in on state from 2 to 40 GHz; it provided better than 25 dB isolation in off state with a capacitance ratio of 94---96. The actuation voltage as low as 1.5 V with actuation area $$110\,\times \,100\,\upmu \mathrm{m^2}$$ 110 × 100 μ m 2 along with good RF performance is reported. The design parameter optimization including selection of appropriate number of meanders and its width found to be one of the most sensitive factors affecting the spring stiffness and actuation voltage.