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The aim of this paper is to investigate the bending characteristics of a low‐pass RF MEMS (radio frequency microelectromechanical system) filter based on a flexible substrate. The proposed filter is achieved by complementary split ring resonator and MEMS bridge which are fabricated on a flexible LCP (liquid crystal polymer) substrate. The bending characteristics of the filter are revealed by theory, simulation and measurement. The experimental results demonstrate that the return loss of the filter deteriorates and the cut‐off frequency of the filter decreases with the curvature of the flexible substrate increasing. The cut‐off frequency is 38.5 GHz and the return loss is −22.7 dB at 10 GHz with the flat substrate. When the curvature of the substrate increases to 28.57 m–1, the cut‐off frequency decreases to 14.8 GHz, and the return loss deteriorates to −5.7 dB at 10 GHz.

Reconfigurable antennas are capable of dynamically altering their frequency, polarization, and radiation properties in a controlled and reversible manner. They modify their geometry and behaviour to maximize the antenna performance in response to changes in their surrounding conditions. To implement a dynamical response, they employ different mechanisms such as PIN diodes, varactors, radio-frequency microelectromechanical systems (RF-MEMS), field effect transistors (FETs), parasitic pixel layers, photoconductive elements, mechanical actuators, metamaterials, ferrites, and liquid crystals. These mechanisms enable intentional distribution of current on the antenna surface producing reversible modification of their properties. This paper presents the design process and applications of reconfigurable antennas. The activation mechanisms of reconfigurable antennas, and their design and operation optimization are discussed. The latest advances on reconfigurable metamaterial engineering, and the current trends and future directions relating to reconfigurable antennas are reviewed. Finally, the applications of reconfigurable antennas in cognitive radio, multi-input multi-output (MIMO) systems, satellite communications, and biomedical devices are highlighted.

A radio frequency microelectromechanical system switch (MSS) manufactured by the complementary metal oxide semiconductor (CMOS) process is presented. The MSS is a capacitive shunt type. Structure for the MSS consists of coplanar waveguide (CPW) lines, a membrane, and springs. The membrane locates over the CPW lines. The surface of signal line for the CPW has a silicon dioxide dielectric layer. The fabrication of the MSS contains a CMOS process and a post-process. The MSS has a sacrificial oxide layer after the CMOS process. In the post-processing, a wet etching of buffer oxide etch (BOE) etchant is employed to etch the sacrificial oxide layer, so that the membrane is released. Actuation voltage for the MSS is simulated using the CoventorWare software. The springs have a low stiffness, so that the actuation voltage reduces. The measured results reveal that actuation voltage for the MSS is 10 V. Insertion loss for the MSS is 0.9 dB at 41 GHz and isolation for the MSS is 30 dB at 41 GHz.

This paper presents a low-cost microfabrication technique for manufacturing radio frequency microelectromechanical system (RF MEMS) switches and varactors without intensive clean-room environments. The fabrication process entails only laser microstructuring technique, non-clean-room microlithography, and standard wet-bench and hot-film emboss of SU-8 and ADEX polymers. MEMS movable structures were fabricated out of 14- $\mu \text{m}$ -thick aluminum foils and suspended above coplanar-waveguide transmission lines, which were implemented on top of FR4 substrates via 5- $\mu \text{m}$ -thick SU-8 dielectric anchors. Both MEMS structures and an FR4 substrate were integrated using micropatterned polymers, developed by using dry-film ADEX and SU-8 polymers, for a composite assembly. An average fabrication yield of higher than 60% was achieved, calculated from 10 fabrication attempts. The RF measurement results show that the RF MEMS devices fabricated by using the novel microfabrication process have good figures of merit, at much lower overall fabrication costs, as compared to the devices fabricated by conventional clean-room process, enabling it as a very good microfabrication process for cost-effective rapid prototyping of MEMS.

Bandpass (BP)-to-bandstop (BS) switchable filters using radio frequency microelectromechanical system switch are presented here. The filters are implemented in both single- and dual-band versions with variable fractional bandwidth (FBW). Tuning of transmission zeros (TZs) and transmission poles (TPs) for BP filter (BPF) and BS filter (BSF), respectively, is achieved in both single- and dual-band cases leading to reconfigurable selectivity. The first odd-mode frequency of the filter is suppressed using a fixed capacitor and the second odd mode is brought closer to the first even-mode with another variable capacitor to form the passband(s). The second capacitor tunes both the second odd mode and TZs (for BPF) or TPs (for BSF) minimizing the requirement of any extra tuning element. In a single-band fabricated BPF, tuning second odd mode gives the FBW variation of 9.3%–72.7% with TZ on the lower side and 5.6%–55.6% with TZ on the higher side of the passband. The 15-dB FBW of a single-band BSF having TP on both sides of the stopband varies over 5.2%–20.7%. The two passbands of a dual-band BPF independently vary over 4.5%–24% and 4.5%–13%. Also, the 15-dB FBW of the first and second stopbands of BSF independently varies over 6.5%–13.2% and 1.5%–3.6%, respectively.

This letter presents characteristics of thermopile-based radio frequency microelectromechanical system (RF MEMS) power sensors with different doped n+ GaAs concentrations, in order to improve sensitivity and signal-noise ratio (SNR). These sensors employ the conversion principle of RF power-heat-electricity, where two materials of AuGeNi/Au and n+ GaAs are designed to constitute two arms of the thermopile. The effects of four doping concentrations of n+ GaAs on the sensitivity and SNR of the power sensors are investigated. The RF MEMS power sensors are fabricated by a GaAs monolithic microwave integrated circuit (MMIC)-compatible process. Experiments show that these power sensors produce return losses of less than −28.3 dB up to 20 GHz. For the doped n+ GaAs concentrations of $2.4\times 10^{{18}}$ , $8.5\times 10^{{17}}$ , $3.2\times 10^{{17}}$ , and $1.9\times 10^{{17}}$ cm−3, measured sensitivities are about 84.10, 101.04, 209.82, and $395.52~\mu \text{V}$ /mW at 1 GHz and about 45.87, 54.11, 104.15, and $212.53~\mu \text{V}$ /mW at 20 GHz, respectively, while the resulting SNR are about $4.27\times 10^{{6}}$ , $3.08 \times 10^{{6}}$ , $3.91\times 10^{{6}}$ , and $5.70\times 10^{{6}}~\text{W}^{{-1}}$ at 1 GHz and about $2.33\times 10^{{6}}, 1.65\times 10^{{6}}$ , $1.94\times 10^{{6}}$ , and $3.06\times 10^{{6}}~\text{W}^{{-1}}$ at 20 GHz, respectively. With the decrease of doping concentration, the sensitivity increases but the SNR decreases first and then increases.

This paper presents a design methodology to drastically improve the hot-switching reliability of contact-type radio frequency microelectromechanical system (RF-MEMS) switches. In the proposed design, sacrificial contacts are placed in parallel with low-resistance contacts to significantly reduce the electric field across the latter. The lower field strength drastically reduces the contact degradation associated with field-induced material transfer. Theoretical and numerical modeling shows that the proposed protection scheme introduces minimal, if any, impact on the RF performance of the switch. To realize the protection scheme, we introduce a novel mechanical design that allows the correct protection actuation sequence to be realized using a single actuator and bias electrode. As a demonstration, several 0–40-GHz RF-MEMS switches are fabricated using a robust copper sacrificial layer technique. Compared with unprotected switches, the protected switch design exhibits over 100 times improvement in the hot-switching lifetime. In particular, we demonstrate a 100–150 million cycle lifetime at 1-W hot switching and 50 million cycles at 2-W hot switching before catastrophic failure, measured in an open-air lab environment. Further optimization of the structural design and contact materials is likely to further increase the hot-switching lifetime.

Radio frequency microelectromechanical system (RF MEMS) switches require a lifetime of 20 years, during which the devices must operate without failure. During operation, the RF MEMS switches are subjected to prolonged actuation which may induce the problems of charge trapping and mechanical relaxation leading to stiction of the moving membrane. In this paper, we suggest an innovative recovery procedure that allows to avoid the stiction. At regular intervals, the switch is opened and an electrical current forced through the suspended membrane can effectively fully recover the switch. Using the topography analysis, we show that the restoring mechanism is based on the recovery of the mechanical properties of the moving bridge during the current flow. The validity of the procedure is demonstrated with the application of the recovery system on several devices for 20 consecutive cycles.

This study presents a 4-bit phase shifter with a maximum phase shift degree of 75° based on packaged metal-contact single-pole double-throw (SPDT) radio frequency microelectromechanical system (RF MEMS) switches mounted on a 20 mil RO4350 substrate and assembled with its driver module on a 4-layer printed circuit board (PCB) board. Electric length of 10° and characteristic impedance of 61.7 Ω are selected for T-stub matching. Standard PCB processing makes it easy to develop and suitable for taking place of mechanical tilt employed in recent base station. Measurements indicate a maximum insertion loss of 1.37 dB at 2.7 GHz and a minimum return loss of 11.71 dB. The phase accuracy is within 1.75° at 2.7 GHz.

This paper presents a radio frequency microelectromechanical system (RF MEMS) based low loss and high transmit-to-receive isolation single-pole-double-throw (SPDT) switch integrated with antenna at 60 GHz for transceiver modules. The device is fabricated on $\boldsymbol{635\ \mu \mathrm{m}}$ alumina substrate using surface micromachining process. SPDT switch features a measured return loss of > 15 dB, insertion loss of 24.6 dB over the frequency band of 55–65 GHz. Total area of the SPDT switch is $\boldsymbol{2.443 \times 0.87\ \text{mm}^{2}}$ . A conventional patch antenna designed at 60 GHz is incorporated at RF-output port of the SPDT switch. The integrated antenna shows a measured return loss of > 25 dB, and 10 dB impedance bandwidth of 8.5% at 60 GHz, when it is connected with either of the input ports of the SPDT switch. Also, a simulated gain of 5.433 dB is observed at 60 GHz. The total area of the integrated device is small enough (8.29 mm2) to fit in 60 GHz T/R modules. Fabricated device is also presented in the paper.

Radio frequency microelectromechanical system(RF-MEMS) technology is suitable for the realization of high-performance reconfigurable wideband radio-frequency passives. The main open issues, i.e., reliability, power handling, packaging, and integration, were effectively addressed across the last 10–15 years, making RF-MEMS technology readiness compatible with commercial applications. From a different perspective, the landscape of 4G-LTE smartphones started to outline the surfacing of performance demands that can be fully addressed by RF-MEMS solutions, i.e., an emerging market-pull rather than technology-push driven scenario. As a result, impedance tuners started to be the first successful commercial exploitation of RF-MEMS technology. Moreover, the upcoming 5G communication standards seem to be the field in which most part of the RF-MEMS value could be extracted. In this chapter, a broad overview on RF-MEMS technology is provided, sketching 15 years of significant achievements reached by the research community, and providing an outlook on future exploitation of such a promising solution.

This tutorial paper presents an empirical model of a capacitive radio frequency microelectromechanical system switch in the microwave domain. The simulation results of the mechanical and electrical aspects of the proposed model were computed with Matlab. The mechanical modeling is validated by COMSOL software through the finite element method to determine the spring constant and the necessary applied voltage. The electromagnetic simulation results are validated by 3 different software: the High-Frequency Structure Simulator based on the finite element method, the Computer Simulation Technology based on finite integration technique method, and the Advanced Design System based on the method of moments. The obtained results are performed in both down (OFF) and up (ON) states in the frequency range of 1 to 40 GHz, and the considered performance benchmarks are the insertion loss, return loss, isolation, and phase.

Microelectromechanical systems (MEMS) have been well known in the field of microelectronics and device technology. The future work deals with review of Radio Frequency Microelectromechanical System phase shifter uniqueness and significance in communication structure. A review of common RF Phase shifter topologies using various devices like PIN diodes and Field-Effect Transistors will be addressed. It presents distributed MEMS transmission line phase shifter design with different transmission line architectures and effect of pull-in voltage on RF MEMS phase shifter.

This paper presents our exploration of microfocus and high-resolution X-ray computed tomography (CT) on open high-aspect ratio through Silicon via (TSV) test structures, the interior wall covered with a ~ 10 μm thick conformal Cu plating, using state-of-the-art and commercially available X-ray systems. Goal of our research is to better understand the physical failure mechanisms of defective open TSVs, in order to further improve the yield of TSV production for integrated passive devices (IPD) to be used in radio frequency microelectromechanical system (RF MEMS) applications. Micrometer-sized defects were non-destructively identified in some of the open TSVs (i.e. Cu plating thickness deviations, incomplete plating and large voids) using microfocus X-ray CT, which were then verified by destructive mechanical cross-sectioning. With high-resolution X-ray CT, which has almost an order of magnitude better resolution, (sub) micron-sized defects in TSVs were directly non-destructively identified and localized, without the need for further destructive inspection techniques for confirmation. The Cu plating thickness variations, in TSVs all connected to a large-area redistribution layer, were found to be design related; based on these failure analysis findings, a new electroplating procedure has been established.

The electrostatic actuation behaviour of the gold bridge in capacitive radio frequency microelectromechanical system switches, fabricated on GaAs substrate, is investigated. An unconventional imaging technique, based on the out-of-focus reflection, was used to evaluate the topographic profile of the suspended bridge and its lowering as a function of the voltage. Important parameters for the switch actuation, such as the pull-down voltage and the air gap between the bridge and the actuator, are estimated. Capacitance-voltage curves allow to evaluate the capacitance associated to the bridge in the up and down states as well as the dielectric constant of the Si3N4 layer, which covers the actuator. The experimental values of the pull-down voltage and the dielectric constant are used to extract from the theoretical equations the residual stress of the fabricated gold membrane. Finally, the current through the dielectric Si3N4 layer was measured as a function of the voltage applied to the actuator, finding that the Poole-Frenkel effect is the dominant conduction mechanism when the switch is actuated.

In the last few years, several low-temperature coefficient of expansion of low temperature cofired ceramic (LTCC) materials have been developed for direct wafer bonding to silicon. BGK, a sodium-containing LTCC, was originally developed for anodic bonding of the sintered LTCC, whereas BCT (bondable ceramic tape) was tailored for direct silicon bonding of green LTCC tapes to fabricate a quasi-monolithic, silicon ceramic compound substrate. This so-called silicon-on-ceramic (SiCer) technique is based on homogeneous nanostructuring of a silicon substrate, a lamination step of BCT and Si, and a subsequent pressure-assisted sintering. We present a new approach for an integrated radio frequency (RF)-platform setup combining passive, active, and mechanical elements on one SiCer substrate. In this context, RF parameters of the Si-adapted LTCC tapes and the use of commercial metal pastes on BCT with respect to bondability and solderability are investigated. We show first technological results of creating cavities at the SiCer interface for SiCer-specific contacting options (e.g., exposed contact pads at the interface), as well as windows in the ceramic layer of the SiCer substrate for additional Si processing (e.g., Si backside thin-film wiring, plasma etching). A further investigated platform technology is deep reactive-ion etching of the SiCer composite substrate. The etching behavior of Si and BCT is demonstrated and discussed. With the SiCer technique, it is possible to reduce the Si content at the setup of RF microelectromechanical system to a minimum (low signal damping).

This work presents a radio frequency microelectromechanical system (RF MEMS) based single-pole-nine-throw (SP9T) switch integrated with an antenna at 60 GHz. The device is fabricated on 635 µm alumina substrate using surface micromachining process. SP9T switch features a simulated return loss of > 14 dB, isolation of > 16 dB and insertion loss of ≤ 0.41 dB over the frequency band of 55–65 GHz. Total area of the SP9T switch is 0.75 mm2. The proposed work is a preliminary prototype for the proof of concept of antenna sectoring at 60 GHz for ISM applications. To validate the principle of operation, a single patch antenna element is incorporated with one of the RF output port of MEMS SP9T switch. The integrated antenna exhibits a simulated return loss of 30 dB, and 10 dB impedance bandwidth of 4.17 % at 60 GHz. Also, a simulated gain of 6.75 dB is achieved, when switch is in actuated state. Total area of the device is ∼ 5.45 mm2. Fabricated device is also presented in the paper.

International audience; This paper presents the design fabrication and measurement of a nanogap radio frequency microelectromechanical system (RF MEMS) metal-contact switch. The prosed device generates a relatively high contact force with a low actuation voltage using a dielectric layer between the actuation electrode and the moveable beam. The actuation voltage is decreased with good reliability of the device by scaling down the gap. Beam geometry optimization allowed reaching 126 micronewtons contact force with only 10 V bias voltage. The fabricated miniature switch (80 × 50 × 0.95 µm) has indeed a pull-down voltage of 6 V and a contact resistance

Reconfigurable antennas offer attractive potential solutions to solve the challenging antenna problems related to cognitive radio systems using the ability to switch patterns, frequency, and polarization. In this paper, a novel frequency reconfigurable E-shaped patch design is proposed for possible applications in cognitive radio systems. This paper provides a methodology to design reconfigurable antennas with radio frequency microelectromechanical system (RF-MEMS) switches using particle swarm optimization, a nature-inspired optimization technique. By adding RF-MEMS switches to dynamically change the slot dimensions, one can achieve wide bandwidth which is nearly double the original E-shaped patch bandwidth. Utilizing an appropriate fitness function, an optimized design which works in the frequency range from 2 GHz to 3.2 GHz (50% impedance bandwidth at 2.4 GHz ) is obtained. RF-MEMS switch circuit models are incorporated into the optimization as they more effectively represent the actual switch effects. A prototype of the final optimized design is developed and measurements demonstrate good agreement with simulations.

This paper presents a novel shunt radio frequency microelectromechanical system switch on a quartz substrate with stiff ribs around the membrane. The buckling effects in the switch membrane and stiction problem are the primary concerns with RF MEMS switches. These effects can be reduced by the proposed design approach due to the stiffness of the ribs around the membrane. A lower mass of the beam and a reduction in the squeeze film damping is achieved due to the slots and holes in the membrane, which further aid in attaining high switching speeds. The proposed switch is optimized to operate in the k-band, which results in a high isolation of -40 dB and low insertion loss of -0.047 dB at 21 GHz, with a low actuation voltage of only 14.6 V needed for the operation the switch. The membrane does not bend with this membrane design approach. Finite element modeling is used to analyze the stress and pull-in voltage.

Reported are the fabrication and thermal stability of an Ru electrode, which is used for a high power Ru–Au contact radio frequency microelectromechanical system switch with a microspring contact design. In this reported work, a new process with bilayer lift-off and a strain release layer is developed, thereby acquiring the 3000 A Ti/Au/Ru electrode with excellent smooth edges for high-power handling capacity and low loss. Furthermore, thermal tests under 400, 500 and 600°C for over 1 h have been performed. Investigation of the surface with scanning electron microscopy and energy dispersive X-ray spectroscopy shows that the electrode has a good thermal stability at 400°C, which is proper for high-power handling. The cold switch DC current handling capacity is advanced from

Microelectromechanical system switches are becoming more and more popular in the electronics industry; there is a need for careful selection of the materials in the design and fabrication of switches for reliability and performance issues. The membrane used for actuation to change the state of an RF switch is made mostly using gold or aluminum. Various designs of membranes have been proposed. Due to the flexure-type structures, the design complexity increases, which makes stress analysis mandatory to validate the reliability and performance of a switch. In this paper, the effective stress and actuation voltage required for different types of fixed-fixed membranes is analyzed using finite element modeling. Effective measures are presented to reduce the stress and voltage.

Presented is a DC-contact radio-frequency (RF) microelectromechanical system symmetric toggle switch for broadband power applications. Based on the lever principle, the proposed switching structure can be toggled upwards with extra restoring force using push electrodes. This push mechanism greatly improves the isolation and efficiently avoids the down-state stiction of the contacts which leads to enhancement of the power-handling capability. The measured actuated voltage is 33.4 V and the contact resistance of the switch can be further decreased to 0.18 Ω under a pull in voltage of 60 V, which results in the improvement of insertion loss. The switch can be properly restored with a voltage of 30 V applied to the push electrode. In addition, the substrate loss is reduced by using a Boroloat™ glass substrate. The RF measurement results show that the switch can handle a minimum 1 W incident RF signal power with isolation and an insertion loss of better than -30 and -0.24 dB from DC to the X-band.

This paper presents the design and measurement of two different switch matrix modules based on Radio Frequency Microelectromechanical System (RF MEMS) switches. The operational frequency range is between 25.5 GHz and 26.5 GHz for data links between a Geostationary Earth Orbit (GEO) relay satellite and Low Earth Orbit (LEO) satellites. The switch matrix implements a key functionality for tracking the incident signals of the LEO satellites on the receive feed antenna array of the GEO satellite's reflector antenna. Two different technologies are used to build simplified switch matrix modules suitable for realizing the full functionality switching matrix. Rogers RT/Duroid 5880 with commercially available RF MEMS is used to build the first module, while EADS in house RF MEMS are integrated in Rogers Ultralam 3850 Liquid Crystal Polymer (LCP) for the second module. Maximum insertion losses of 8.5 dB and 10.2 dB have been measured for the Rogers RT/Duroid 5880 and the LCP module, respectively. Isolation is higher than 45 dB and a minimum return loss of 15 dB is shown. Finally, the measured losses in the LCP module are analyzed and suitable improvements are discussed.

Radio frequency microelectromechanical system (RF MEMS) is a promising technology in the field of wireless communications. MEMS mixers and filters offer remarkable advantages in term of size, cost, and power consumption over conventional devices. One of the MEMS materials that have very good mechanical and electronic characteristics is Silicon carbide (SiC). In this work, A SiC electrostatic actuator, resonating at fundamental frequency of 66.64 kHz, was fabricated and designed to perform frequency mixing. Two signals with different frequencies were multiplied and the sum, as well as the difference of the two frequencies, was used to drive the fabricated cantilever into resonance.

The contact reliability issue in ohmic radio frequency microelectromechanical system switches is particularly challenging due to their low actuation force (the contact/restoring force is typically on the scale of 100 μN or less) and small device geometry (the typical dimensions are from 1 to 100s μm). As a result of the low actuation force, the breaking surface adsorbed film becomes difficult; thus, the contact resistance is extremely sensitive to surface condition in the contact area. In addition, a low restoring force during switch operation could cause stiction issue, especially for pure gold microcontacts. In addition, due to the fundamental scaling law, the risk of applying current or voltage to microswitches becomes much larger due to worsened heat constriction and enhanced electrical field in the microscale structures. In this article, we review recent experimental efforts to address these issues so that an improved understanding of the contact reliability in ohmic microelectromecha...

This paper presents an integrated solution for wafer-level packaging and electrostatic actuation of out-of-plane radio frequency microelectromechanical system resonators. By integrating the electrodes into the epitaxial-grown silicon layer, both the encapsulation and the out-of-plane actuation can be built in one process step, which results in an ultracompact and robust packaging. First, designs and fabrication processes of the out-of-plane electrode are described. The mechanical and electrical properties of the electrode are discussed, modeled, and characterized. A 200 kHz torsional mode beam resonator and an 11.2 MHz transverse-mode differential square plate resonator are fabricated using this packaging method and their performances are presented and discussed.

This article gives an overview of applications of radio frequency (RF) microelectromechanical system (MEMS) technology in radio detection and ranging (radar). RF MEMS components for radar include attenuators, limiters, (true-time-delay) phase shifters, transmit/receive (T/R) switches and tunable matching networks. Radar subsystems that benefit from RF MEMS technology include active electronically scanned arrays (T/R modules), passive electronically scanned arrays (lenses, reflect arrays, subarrays, and switched beamformers), and radomes. Using a bottom-up approach, the figures of merit for RF MEMS technology are related to the figures of merit for radar subsystems. The article also discusses ultrawideband RF MEMS reflect array and T/R module design as examples. First, electronically scanned array, radar and RF MEMS fundamentals are briefly introduced.

This letter demonstrates a 20-GHz radio frequency microelectromechanical system (RF MEMS)-based electrically switchable antenna on a quartz substrate. Two quasi-Yagi antenna elements are monolithically integrated with a single-pole double-throw (SPDT) MEMS switch router network on a 21 mm times 8 mm chip. Electrical beam steering between two opposite directions is achieved using capacitive MEMS SPDT switches in the router. Port impedance and radiation patterns are studied numerically and experimentally. Measured results show that the switched beam antenna features a 27% impedance bandwidth (S11 = -10 dB), a gain of 4.6 dBi, and a front-to-back ratio of 14 dB at 20 GHz when the control voltage is applied to one of the switch pairs of the SPDT switch.

International audience; The present work first provides an experimental technique to study self-heating of bulk acoustic wave (BAW) resonators under high RF power in the gigahertz range. This study is specially focused on film bulk acoustic wave resonators and solidly mounted resonators processed onto silicon wafers and designed for wireless systems. Precisely, the reflection coefficient of a one-port device is measured while up to several watts are applied and power leads to electrical drifts of impedances. In the following, we describe how absorbed power can be determined from the incident one in real time. Therefore, an infrared camera held over the radio frequency micro electromechanical system (RF-MEMS) surface with an exceptional spatial resolution reaching up to 2 µm/pixels gives accurate temperature mapping of resonators after emissivity correction. From theoretical point of view, accurate three-dimensional (3-D) structures for finite-element modeling analyses are carried out to know the best materials and architectures to use for enhancing power handling. In both experimental and theoretical investigations, comparison is made between film bulk acoustic wave resonators and solidly mounted resonators. Thus, the trend in term of material, architecture, and size of device for power application such as in transmission path of a transceiver is clearly identified.

This paper presents the development of π-type radio-frequency-microelectromechanical system (RF-MEMS) capacitive shunt switches using 50 nm thick amorphous hafnium oxynitride (HfO x N y ) dielectric film as insulator layer. The 50 nm-thick amorphous HfO x N y film was prepared by reactive sputtering. The electrical properties of the HfO x N y film were investigated with a capacitance-voltage, current-electric field and constant bias stressing measurement. The HfO x N y film had a dielectric constant of 19 at 1 MHz and a dielectric strength of 9.5 MV/cm. The HfO x N y dielectric film exhibited excellent reliability during constant bias stressing. The insertion loss of the RF-MEMS capacitive switch at the up-state was lower than 0.35 dB in frequencies up to 10 GHz, 0.5 dB at 10 to 15 GHz and 0.8 dB at 26 GHz. The switch at down-state had isolation performance better than −30 dB in the frequency range of 10 to 20 GHz, and −27 dB in the frequency range of 20 to 30 GHz.

The static and modal characteristics of capacitive-coupling membrane-type radio-frequency (RF) microelectromechanical-system (MEMS) switches are comprehensively investigated by the finite element method. Static characteristics including displacement, stress, effective stiffness constant, and actuation voltage, and modal characteristics such as natural frequency and switching time are studied. The structures and the materials of the switches are the main factors that determine switch performance. The study focuses on how the static and modal characteristics of the RF MEMS switches are affected by their structures and materials.

Optically actuated radio frequency microelectromechanical system (MEMS) devices are seen to self-oscillate or vibrate under illumination of sufficient strength (Aubin, Pandey, Zehnder, Rand, Craighead, Zalalutdinov, Parpia (Appl. Phys. Lett. 83, 3281–3283, 2003)). These oscillations can be frequency locked to a periodic forcing, applied through an inertial drive at the forcing frequency, or subharmonically via a parametric drive, hence providing tunability. In a previous work~(Aubin, Zalalutdinov, Alan, Reichenbach, Rand, Zehnder, Parpia, Craighead (IEEE/ASME J. Micromech. Syst. 13, 1018–1026, 2004)), this MEMS device was modeled by a three-dimensional system of coupled thermo-mechanical equations requiring experimental observations and careful finite element simulations to obtain the model parameters. The resulting system of equations is relatively computationally expensive to solve, which could impede its usage in a complex network of such resonators. In this paper, we present a simpler model that shows similar behavior to the MEMS device. We investigate the dynamics of a Mathieu–van der Pol–Duffing equation, which is forced both parametrically and nonparametrically. It is shown that the steady-state response can consist of either 1:1 frequency locking, or 2:1 subharmonic locking, or quasiperiodic motion. The system displays hysteresis when the forcing frequency is slowly varied. We use perturbations to obtain a slow flow, which is then studied using the bifurcation software package AUTO.

The objective of the paper is to design a single-pole double-throw (SPDT) radio frequency microelectromechanical system (RF MEMS) switch for ultra-broadband applications. The SPDT RF MEMS switch is driven by rotary comb-drive actuators with lateral resistive contacts. The proposed fabrication process of the switch is a standard nickel electroforming process on a glass substrate. Chosen electrostatic actuators decrease the power consumption of the switch near to zero and provides good contact force which results less contact resistance. As a result, good RF characteristics were achieved. The designed SPDT RF MEMS switch has a drive voltage of 50V, switching times from OFF to state I or II and vice versa shorter than 79μs and 130μs, an insertion loss below −0.73dB up to 90GHz, a return loss below −16.43dB and an isolation below −23.91dB.

Cognitive radio is an emerging technology for efficient use of the radio spectrum where the spectrum can be used by the unlicensed users without interference with the licensed user. Reconfigurable antennas offer attractive potential solutions to solve the challenging antenna problems related to cognitive radio systems using the ability to switch patterns, frequency and polarization. In this work, a novel frequency reconfigurable E-Shaped patch design is proposed for possible applications in cognitive radio systems. This work provides a methodology to design reconfigurable antennas with Radio Frequency Microelectromechanical System (RF-MEMS) switches. The reconfigurability is achieved in the frequency ranges from 2.2GHz to 4.2GHz respectively. The frequency reconfigurability is done to switch between the frequencies in the cognitive radio. The RF-MEMS switch is used to change the dimensions of the patch to make the antenna to resonate for various frequencies.

Development of packaging is one of the critical issues toward realizing commercialization of radio-frequency-microelectromechanical system (RF-MEMS) devices. The RF-MEMS package should be designed to have small size, hermetic protection, good RF performance, and high reliability. In addition, packaging should be conducted at sufficiently low temperature. In this paper, a low-temperature hermetic wafer level packaging scheme for the RF-MEMS devices is presented. For hermetic sealing, Au-Sn eutectic bonding technology at temperatures below 300°C is used. Au-Sn multilayer metallization with a square loop of 70 µm in width is performed. The electrical feed-through is achieved by the vertical through-hole via filling with electroplated Cu. The size of the MEMS package is 1 mm × 1 mm × 700 µm. The shear strength and hermeticity of the package satisfies the requirements of MIL-STD-883F. Any organic gases or contamination are not observed inside the package. The total insertion loss for the packaging is 0.075 dB at 2 GHz. Furthermore, the robustness of the package is demonstrated by observing no performance degradation and physical damage of the package after several reliability tests.

This work describes the integration of commercially available packaged radio frequency microelectromechanical system (RF MEMS) switches with radiation pattern reconfigurable microstrip antennas. Most applications of RF MEMS switches consider the switches as only circuit elements. In contrast, the implementation of packaged switches in this particular antenna must address not only the simple open/closed behavior of the switches but also their impact on the radiation characteristics of the reconfigurable antenna. Here, two Radant MEMS single-pole single throw (SPST) SPST-RMSW100 (packaged RF MEMS) switches are used to reconfigure the radiation patterns of a resonant square spiral microstrip antenna between endfire and broadside over a common impedance bandwidth. Switch insertion, matching network design, and other issues are addressed. Results for both simulated and measured antennas, as well as recommendations for future work in this area, are provided.

In this paper, a new method for suppressing microwelding on the RF MEMS (Radio Frequency Microelectromechanical System) direct contact switches is introduced. Two kinds of refractory metals, tungsten and molybdenum were coated onto the contact point of the switches and the effect of the coating was examined. The changes in insertion loss and isolation at the switch were measured by using network analyzer and power loss was evaluated by power measurement. The results revealed that while tungsten and molybdenum showed higher contact resistance than gold in low input power range, they enhanced the power handling capability and reliability of the switches in high input power region.

For the comb-drive design of microelectromechanical systems (MEMSs), the driving force due to the electrostatic field is very important, and an accurate electrostatic analysis is essential and indispensable. For various gaps, finger width ratios and travelled distances of the comb drive of MEMSs, the dual boundary element method (DBEM) has become a better method than the domain-type finite element method because the DBEM can provide a complete solution in terms of boundary values, with substantial saving in modelling effort. In this article, the DBEM is used to simulate the fringing field around the edges of the fixed and movable fingers of the comb drive of an MEMS for diverse design cases, and many electrostatic problems for typical comb drive designs of MEMSs are analysed, investigated and compared with a widely used approximate method. Results show that the driving force is obviously dependent on the travelled distance, and the approximate method cannot work well for all travelled positions because there is an apparent error (not less than 10 per cent), especially at the beginning and ends of the range of travel. In addition, the smaller the gap between movable and fixed fingers, the larger the driving force is, and the error of approximate method also becomes more and more predominant as the gap decreases. The results also demonstrate that the difference between the DBEM and the approximate method effect due to finger width ratio is very small. Using the DBEM presented in this article, an accurate and reasonable electrostatic field can be obtained, and the follow-up control method of driving force for the comb drive of an MEMS can be implemented more precisely.

A series of surface micromachined microelectromechanical system switches with composite metal beams were fabricated by standard photolithographic techniques. The study was conducted in order to assess the influence of film stress and composition on the released shape of cantilever and fixed-fixed beam structures. A 1 μm thick evaporated Au film was the basis for all bridge materials with additional 20 nm layers of evaporated or sputter deposited Ti, Pt, W, or Au on the top or bottom surface of the thick Au. The planarity and stress gradient of cantilever beam structures and the planarity of fixed-fixed beam structures were measured by optical interferometry. Gold-only bridge structures displayed the best planarity of those examined while structures with Ti layers displayed the least planarity. Cantilever stress gradients calculated using both cantilever-tip deflection and radius of curvature techniques were typically between 9 and 16 MPa/μm. The thin film biaxial moduli used in stress gradient calculation...