RF MEMS Technology Research Articles

MEMS Micro-Era Missile-Borne

This article describes the basic meaning, features and foreign developments of the MEMS-IMU and the RF-MEMS technology, presents and analyzes the research and the actual application of the MEMS technology in missile guidance, navigation, data link, detection, control, etc. and the changes carried out by MEMS missile technology.

RF MEMS for Reconfigurable RF Front-End: Research in Australia

This paper reviews some ground breaking development of RF MEMS technology in Australia at the UNSW, over the past decade. It presents some unique and novel designs using RF MEMS switches to achieve reconfigurable RF front-end circuits. These designs include multiport RF MEMS switches, switch matrices, reconfigurable filters and antennas. The resulting devices achieved RF performance that is unmatched by any existing RF andmicrowave technologies.

Design of RF MEMS based switch matrix for space applications

Abstract. RF MEMS based switch matrices have several advantages compared to the mechanical or solid-state switch based ones for space applications. They are compact, light and less lossy with a high linearity up to high frequency. In this work, a 12 × 12 switch matrix with RF MEMS and LTCC technologies is presented based on the planar Beneš network. The simulated performance of the 12 × 12 switch matrix is below −12 dB IL (Insertion Loss) up to C band and −15 dB RL (Return Loss) up to Ku band. Moreover, it has a good isolation better than −50 dB. A 4 × 4 switch matrix with the same design process and technologies is fabricated and measured to verify the 12 × 12 switch matrix design process. The measured performance agrees very well to the simulations.

Handling RF Power: The Latest Advances in RF-MEMS Tunable Filters

RF-MEMS technology permits practical implementations of high-Q (Q from 300 to over 1,000) tunable microwave filters with power handling in the >;1-10 W range, with significant tuning range (>;50% to 100%), and ultra-low power consumption. Continuously frequency-tunable filters with mechanical actuation in the opposite direction of RF-inducted pressure can reach powers up to several watts, using a variable compensation bias. Very high Q, and large tuning range can be achieved with this technology, both in planar and cavity tunable filters. Using several devices in parallel, RF-MEMS capacitor arrays can handle RF-powers better than 1 watt, without the need for any compensation tuning.

Modeling and simulation of an active restoring mechanism for high reliability switches in RF-MEMS technology

We present a comprehensive study on a high reliability RF-MEMS switch with an active thermal recovery capability to counteract stiction. Applying finite element (FE) simulations we investigate the complete recovery process including mechanical, electrical, thermal and fluidic effects. The experimentally calibrated thermo-mechanical FE-model is used to extract key parameters of the recovery process. Therewith we are able to estimate the efficiency of the recovery capability and to figure out possible design improvements in order to optimize the investigated switch with respect to reliability.

RF-MEMS switches with AlN dielectric and their applications

This paper reports on the potential of RF-MEMS technology based on aluminum nitride capacitive dielectric and nickel-suspended membranes to provide RF circuit functions in reconfigurable front-end radios. The RF performance of capacitive switches, distributed MEMS transmission lines (DMTLs) phase shifters for beam steering and tunable filters, including center frequency and bandwidth tuning of bandpass and band-stop filters are presented. Detailed characterization based on S-parameter data demonstrates very promising figures of merit of all fabricated demonstrators from 5 to 40 GHz.

High-$Q$ RF-MEMS 4–6-GHz Tunable Evanescent-Mode Cavity Filter

This paper presents a miniature high-Q tunable evanescent-mode cavity filter using planar capacitive RF microelectromechanical system (MEMS) switch networks and with a frequency coverage of 4.07-5.58 GHz. The two-pole filter, with an internal volume of 1.5 cm3, results in an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, and an ultimate rejection of > 80 dB. RF-MEMS switches with digital/analog tuning capabilities were used in the tunable networks so as to align the two poles together and result in a near-ideal frequency response. The measured Qu of the filter is 300-500 over the tuning range, which is the best reported Q using RF-MEMS technology. The filter can withstand an acceleration of 55-110 g without affecting its frequency response. The topology can be extended to a multiple-pole design with the use of several RF-MEMS tuning networks inside the evanescent-mode cavity. To our knowledge, these results represent the state-of-the-art in RF-MEMS tunable filters.

Tunable dual-frequency RF MEMS rectangular slot ring antenna

This paper presents the design, fabrication, and measurement of a novel, tunable, dual frequency rectangular slot antenna using RF MEMS technology. The antenna tuning is achieved by electrostatically actuated RF MEMS variable capacitors on a stub. Two different capacitor structures are implemented on the antenna: cantilever type and fixed–fixed beam type. The latter one is not sensitive to the stress on the structural layer and its measurement results agree well with the simulation results. Each antenna is fabricated monolithically using an in-house surface micromachining RF MEMS process on a 500-μm thick glass substrate and occupies an area of about 21 mm × 18 mm. The measurement results show that the antenna resonant frequency can be tuned in a 1 GHz range in the X-band.

Tuning in to RF MEMS

RF MEMS technology was initially developed as a replacement for GaAs HEMT switches and p-i-n diodes for low-loss switching networks and X-band to mm-wave phase shifters. However, we have found that its very low loss properties (high device Q), its simple microwave circuit model and zero power consumption, its high power (voltage/current) handling capabilities, and its very low distortion properties, all make it the ideal tuning device for reconfigurable filters, antennas and impedance matching networks. In fact, reconfigurable networks are currently being funded at the same level-if not higher-than RF MEMS phase shifters, and in our opinion, are much more challenging for high-Q designs.

RF MEMS status and perspectives

AbstractThe key challenges for the next generation of communication architectures are related to their ability to modify their properties in order to fit with different applications and environmental conditions. Among the emerging approaches targeting these miniaturized systems called “Smart Microsystems”, RF MEMS technology is considered as one of the most attractive and enabling solution. This paper will outline the main characteristics exhibited by RF MEMS technologies as well as the main technological process flow, the design and modelling methodologies that have to be implemented in order to meet the multi‐physics and multi‐scale challenge encountered in this field. The paper will continue with a major issue faced by RF MEMS related to reliability. Finally, the paper will finish with the presentation of innovative smart devices and systems that could be envisioned in the future. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

RF-MEMS for Wireless Communications

This article presents an introduction and overview of MEMS technology with a focus on RF applications of MEMS in the design of cellular handsets. A novel, integrated, high-Q tunable digital capacitor is discussed to demonstrate how RF-MEMS technology can be utilized to make high frequency components whose RF characteristics can be adjusted during operation, allowing for the first time reconfiguration of radio hardware under software control. It is concluded that as the consumer wireless market continues to grow and evolve, product designers will remain under ever increasing pressure to develop smaller, lighter, thinner products that are more functional, energy-efficient, and intuitive, and to do so faster and at lower cost. Although issues and challenges persist, opportunities abound, and RF-MEMS technology holds the promise of being a key enabler of future generations of more highly converged, cognitive, and flexible consumer wireless products.

An electrostatic fringing-field actuator (EFFA): application towards a low-complexity thin-film RF-MEMS technology

This paper presents a novel electrostatic actuator using fringing fields as the actuation mechanism, i.e. an electrostatic fringing-field actuator or EFFA. The novel device is produced on an insulating substrate in a simple two-mask process involving only one sacrificial layer and one metallization. To demonstrate the EFFA capabilities, we produced and characterized EFFAs in various technological implementations of remarkable simplicity. This simplicity allows a vast flexibility for the processing and as a result strongly eases the integration of the EFFAs into existing technologies. For the basic device, we report a non-de-embedded measured capacitance ratio of 1:3 and a lifetime of more than 107 cycles with 40 V bipolar actuation at 100 Hz in N2 atmosphere. Both the capacitance ratio and the C–V profile were tuned by modifying the technology, e.g. coating the substrate before processing the EFFAs and the design, e.g. switching from clamped-free to clamped–clamped devices. We finally report a complete RF-MEMS technology using the EFFAs as single actuators. Switchable and tunable LC tanks, phase shifters, series and shunt parallel-plate capacitors actuated as relays and capacitive relays are presented to demonstrate the possibilities of this technology.

RF MEMS technology

AbstractRecently, to meet the demands of multimode/multiband functions for the next generation communication systems, RF MEMS technology is being developed for the reconfigurable transceiver system. In this article, RF MEMS devices such as switches, high‐Q inductors, and high‐Q resonators are reviewed for their operating principles and device structures, as well as the reliability and commercial issues. Single pole single throw (SPST)‐type MEMS switches show characteristics superior to solid‐state switches in the aspects of insertion loss, isolation, and linearity. Single pole multithrow (SPMT) switches will enable ultra small‐sized cellular phones, but insertion loss and coupling between channels should be improved. For a high‐Q inductor, out‐of‐plane inductors show improved results, and an inductor with a Q‐factor of 75 at 1GHz has been fabricated by using the internal stress of a MoCr film. The MEMS inductor improves the performance of a voltage controlled oscillator (VCO), but proper hermetic packaging and standard libraries are also necessary for mass production. The MEMS resonator can operate up to 1.4 GHz and can be used as an oscillator for the timing device as well as component of the filter circuit. The SiTime Company recently has started delivery of a product with performance similar to the quartz oscillator, in which they solved the reliability issues by modifying the annealing and vacuum packaging. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

RF MEMS--Enabling Technology for Millimeter-Waves

This paper presents high-performance millimeter-wave passive devices using MEMS technology. The purpose of this paper is to show the possibility of MEMS technology as an enabling technology for millimeter-waves. The loss and cost issues, which have been the inherent barrier for commercialization of mm-waves, can be solved by RF MEMS technology. Successful demonstrations of MEMS technology for mm-waves include novel CPW transmission lines, digital impedance tuners, analog tunable band-pass filters, reconfigurable low-pass filters, V-band digital distributed phase shifters and 2-D mechanical beam-steering antennas. All these circuits were implemented for 30-65 GHz frequency range, and show the state-of-the-art performance, which is beyond the limit set by the conventional technology.

RF MEMS and NEMS technology, devices, and applications

Will RF MEMS deliver on its promise to be one of the major MEMS businesses in the future? RF MEMS has now entered its second generation; high-volume production of both contacting and non-contacting switches and filters (based on bulk acoustic waves) was ramped up worldwide starting in 2003. In first-generation RF MEMS, discrete components were developed to demonstrate RF performance and reliability, and low-cost, high-volume chip- and wafer-scale packaging eliminated the final barriers to high-volume production of discrete replacement components with MEMS. In this paper, we review the RF MEMS industry and the commercialization status of RF MEMS components. We also provide a detailed case study of mobile telephone basestations, demonstrating how RF MEMS can impact telecommunications. Finally, we look at research into third-generation RF MEMS and NEMS, in which integration, active devices, and new functionality will create opportunities for disruptive changes in RF subsystems, enabling such things as software-defined radio.

A Reconfigurable Spiral Antenna for Adaptive MIMO Systems

We present a reconfigurable spiral antenna for use in adaptive MIMO systems. The antenna is capable of changing the sense of polarization of the radiated field. It is fabricated by using an RF-MEMS technology compatible with microwave laminate substrates developed within the author's group. The proposed antenna structure is built on a number of rectangular-shaped bent metallic strips interconnected to each other with RF-MEMS actuators. Two senses of polarization, RHCP and LHCP, are achieved by configuring the physical structure of the antenna, that is, by changing the winding sense of the spiral, through judicious activation of MEM actuators. The fabrication process for the monolithic integration of MEM actuators with bent microstrip pixels on RO4003-FR4 microwave laminate substrate is described. The measured and calculated radiation and impedance characteristics of the antenna are given. The operating frequency of the presented antenna design can easily be adjusted to be compatible with popular IEEE networking standards such as 802.11a.

RF MEMS theory, design, and technology [Book Review

RF MEMS theory, design, and technology [Book Review

Review of radio frequency microelectromechanical systems technology

A review of radio frequency microelectromechanical systems (RF MEMS) technology, from the perspective of its enabling technologies (e.g. fabrication, RF micromachined components and actuation mechanisms) is presented. A unique roadmap is given that shows how enabling technologies, RF MEMS components, RF MEMS circuits and RF microsystems packaging are linked together; leading towards enhanced integrated subsystems. An overview of the associated fabrication technologies is given, in order to distinguish between the two distinct classes of RF microsystems' component technologies; non-MEMS micromachined and true MEMS. An extensive literature survey has been undertaken and key papers have been cited; from these, the motivations behind different RF MEMS technologies are highlighted. The importance of understanding the limitations for realising new and innovative ideas in RF MEMS is discussed. Finally, conclusions are drawn as to where future RF MEMS technology may lead. It is likely that the switch will continue to be the most important RF MEMS component, with future work investigating its enhanced functionality, subsystem integration and volume production. The focus of RF MEMS circuits will shift from the digital phase shifter to high-Q tuneable filters.