1,720,964 research outputs found
Modeling and simulation of an active restoring mechanism for high reliability switches in RF-MEMS technology
No full textWe 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
A reconfigurable impedance matching network entirely manufactured in RF-MEMS technology
No full textIn this work we present a reconfigurable impedance matching network for RF (Radio Frequency) applications, entirely manufactured in MEMS technology (RF-MEMS). The network features four impedance sections. The way they load the RF line (i.e. in series or shunt configuration) as well as the type of impedance they realize (purely capacitive, inductive, or both in parallel) are reconfigured by means of RF-MEMS cantilever-type ohmic switches. A few specimen of the network have been fabricated using the RF-MEMS technology platform available at FBK and experimentally characterized. In particular, the electromechanical characteristic of the RF-MEMS switches is observed, and the upward bending of the switches contact tips made the characterization of the RF behavior impossible. The non-planarity is due to the accumulation of residual stress within the suspended Gold layer during the release of suspended structures, and is currently being mitigated by performing a low-temperature release step. Electromagnetic simulations (S-parameters) of the RF-MEMS network are also reported in this paper, showing the wide range of impedance transformations enabled by such a complex device based on MEMS technology
Electromechanical and Electromagnetic Simulation of RF-MEMS Complex Networks Based on Compact Modeling Approach
No full textRF-MEMS, i.e. MicroElectroMechanical-Systems for Radio Frequency applications, have been attracting the interest of the scientific community for more than one decade, thanks to their high performance and large reconfigurability. The employment of RF-MEMS based devices and networks, like varactors, switches, phase-shifters, impedance matching networks and so on, within transceivers platforms, is the key to extend their functionalities and supported services. In this scenario, it is straightforward that the proper simulation of RF-MEMS devices and networks is a critical aspect to be faced, aiming at their integration within functional blocks based on standard semiconductor technologies. Our contribution reports on the exploitation of a MEMS compact model software library, previously developed by some of the authors, in order to simulate the coupled electromechanical and RF behavior of RF-MEMS devices/networks within a commercial ICs development framework, i.e. Cadence©. Such an approach enables the fast and accurate simulation of the mixed-domain behavior of RF-MEMS, as well as the hybridization of RF MEMS and CMOS blocks within the same schematic
Improving the reliability of electrostatically actuated RF-MEMS switches: FEM simulations and measurements on a thermal recovery mechanism
No full textWe present a detailed study on an active thermal recovery mechanism intended to counteract stiction in an electrostatically actuated RF-MEMS switch. A problemadapted, hierarchized analysis procedure based on a recently derived and presented finite element (FE) model has been applied to investigate the impact of different design and material parameters on the efficiency of this mechanism as well as on the overall operation of the device. The simulation results are discussed with respect to the device operation in case of stiction due to micro-welding or other adhesive forces and are compared to optical measurements. From the presented results guidelines are derived on how the recovery mechanism and, herewith, the reliability of the switch may be improved by design
Study of an active thermal recovery mechanism for an electrostatically actuated RF-MEMS switch
No full textWe present a comprehensive study on an electrostatically actuated RF-MEMS switch with active thermal recovery capability intended to counteract stiction. On the basis of finite element (FE) simulations a detailed model including all relevant physical effects has been developed to investigate this recovery mechanism. The resulting model enables to reproduce the whole recovery process during a failure situation of the switch, proving its functionality and, thus, identifying and elaborating possible design improvements. The simulated results are confirmed by experimental data obtained from white-light interferometry (VEECO) and laser-Doppler vibrometry (Polytec)
Analysis of RF-MEMS Switches in Failure Mode: Towards a More Robust Design
No full textWe present comprehensive theoretical and experimental investigations on one of the most relevant failure mechanisms in RF-MEMS switches, namely electrically induced stiction. In particular, we analyze an RF-MEMS switch equipped with an embedded active thermal recovery appliance by deriving and applying a 3D, problem-adapted, coupled finite element (FE) model including all relevant mechanical, electrical, thermal, and fluidic effects. The accuracy and predictive power of the simulations is ensured by a dedicated calibration procedure based on highly accurate characterization techniques such as white light interferometry and laser Doppler vibrometry. Applying the calibrated model, we studied the switch operation during failure and recovery in all details and identified the most important design parameters affecting its reliability with a view to improving the recovery capability as well as optimizing the overall performance towards a more robust switch design
An Energy Harvester Concept for Electrostatic Conversion Manufactured in MEMS Surface Micromachining Technology
No full textIn this work we present the concept of a MEMS-based Energy Harvester (EH) for the conversion of vibration into electrical energy. The employed electrostatic conversion mechanism of the device is sensitive both to vertical (out-of-plane) and horizontal (in-plane) displacements, thanks to the presence of buried planar and interdigitated fixed electrodes, respectively. The proposed EH is inexpensively manufactured in the MEMS/RF-MEMS surface micromachining process available at Fondazione Bruno Kessler (FBK) in Italy, and, thereby, does not require any specific technology modification to be realized. Modeling of the EH concept (Finite Element Method based and analytical) is reported and discussed, and validated against preliminary experimental measurements. The structure exhibits resonant frequencies in the range up to 10-12 kHz, it being compatible with vibration sources typically available in the surrounding environment, like busy street, car engine, industrial and domestic appliance, and so on. Preliminary estimates of the power conversion capability seem to address rather low levels (in the range of pW), despite, on the other hand, the EH design as well as the fabrication process admit significant margins of performance improvement
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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