4,692 research outputs found

    Towards uniqueness of degenerate axially symmetric Killing horizon

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    We examine the linearized equations around extremal Kerr horizon and give some arguments towards stability of the horizon with respect to generic (non-symmetric) linear perturbation of near horizon geometry.Comment: 17 page

    A Fully Parameterized Fem Model for Electromagnetic Optimization of an RF Mems Wafer Level Package

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    In this work, we present a fully parameterized capped transmission line model for electromagnetic optimization of a wafer level package (WLP) for RF MEMS applications using the Ansoft HFSS-TM electromagnetic simulator. All the degrees of freedom (DoF's) in the package fabrication can be modified within the model in order to optimize for losses and mismatch (capacitive and inductive couplings) introduced by the cap affecting the MEMS RF behaviour. Ansoft HFSS-TM was also validated for the simulation of capped RF MEMS devices by comparison against experimental data. A test run of capped 50 transmission lines and shorts was fabricated and tested.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

    Parasitic Effects Reduction for Wafer-Level Packaging of RF-Mems

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    In RF-MEMS packaging, next to the protection of movable structures, optimization of package electrical performance plays a very important role. In this work, a wafer-level packaging process has been investigated and optimized in order to minimize electrical parasitic effects. The RF-MEMS package concept used is based on a wafer-level bonding of a capping silicon substrate to an RF-MEMS wafer. The capping silicon substrate resistivity, substrate thickness and the geometry of through-substrate electrical interconnect vias have been optimized using finite-element electromagnetic simulations (Ansoft HFSS). Test structures for electrical characterization have been designed and after their fabrication, measurement results will be compared with simulations.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

    Bulk-micromachined tunable fabry–perot microinterferometer for the visible spectral range

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    The design, fabrication and measured characteristics of a bulk-micromachined tunable Fabry–Perot microinterferometer (FPMI) for the visible spectral range are presented. The FPMI is formed by two parallel 40 nm thick silver mirrors supported by a 300 nm low tensile stress silicon nitride membrane with a square aperture (side length of 2 mm) and initial cavity gap of 1.2 µm. One of the mirrors is fixed, the other is under tension on a movable Si frame, which is electrostatically deflected, using several distributed electrodes, to control cavity spacing and mirror parallelism. Performance achieved is: high flatness of the mirrors (λ/10 for the visible part of the spectrum), low control voltages (<21 V for 450 nm deflection) and simple fabrication.Fundação para a Ciência e Tecnologia (FCT

    Micromachined fabry-perot optical filters

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    The design, fabrication and measured characteristics of micromachined Fabry- Perot (F-P) optical filters for the visible spectral range are presented. Silver films of 40-50 nm thickness, evaporated on a 300 nm thick low-stress silicon nitride membrane, are used as high-quality mirrors. Two parallel mirrors, with a square aperture of up to 2x2 mm2 and initial cavity gap of 1.2 µm, form a tunable Fabry- Perot optical filter. One of the mirrors is fixed the other is under tension on a movable Si frame, which is electrostatically deflected to control the mirror spacing and parallelism. Results are compared with non-tunable F-P filters that are composed of an Ag/SiN/Ag or Ag/SiO2/Al layer stack. The FWHM of 40 nm (tunable filter) and 16 nm (non-tunable filter) have been achieved.STW - Project DEL 55.3733. Junta Nacional de Investigação Científica e Tecnológica - PRAXIS XXI-BD/5181/95

    High-selectivity single-chip spectrometer in silicon for operation at visible part of the spectrum

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    A microspectrometer has been realized based on an array of Fabry–Perot optical thin-film filters. The 16-channel microspectrometer is compatible with IC fabrication methods and operates in the visible spectral range with an interchannel shift of 6 nm. Each of the channels is sensitive in a single peak with full-width-half-maximum (FWHM) of 16 nm. Also aFWHMbelow 2 nm and finesse of 40 for narrow band operation is demonstrated. The device can easily be tuned during fabrication to cover a different spectral band only by adjusting the etching times without affecting the device layout. Such a device is extremely suitable for applications in microsystems because of its small size, high spectral selectivity, and low cost. Microspectrometers for the UV and IR regions are also feasible using this technique.Fundação para a Ciência e a Tecnologia (FCT

    Silver-based reflective coatings for micromachined optical filters

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    Silver films of 40 nm thickness, evaporated on a 300 nm thick low-stress silicon nitride layer, are used as high-quality mirrors operating in the visible and near IR spectral range. Application of a silicon nitride membrane under tension, placed within a square Si frame after bulk micromachining, improves the initial mirror flatness. Two parallel mirrors, each with square aperture of up to 2x2 mm2 and an electrostatically controlled spacing, form a tunable Fabry–P´erot optical filter. Investigation of the silver-based reflective coatings, and mirror characterization, including influence of bulk micromachining, are presentedFundação para a Ciência e a Tecnologia FC

    High-selectivity single-chip spectrometer for operation at visible wavelengths

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    A micro-spectrometer has been realized based on an array of Fabry-Perot thin-film optical resonators. The 16 channel micro-spectrometer is IC fabrication compatible and operates in the visible spectral range with an inter-channel shift of 6 nm. Each of the channels is sensitive in a single peak with FWHM of 16 nm. A FWHM < 2 nm and finesse of 40 for narrowband operation is demonstrated.STW - Project DEL 55.3733. TUDelft. Fundação para a Ciência e Tecnologia - Praxis XXI-BD/5181/95

    A local bus for MCM-based microinstrumentation systems

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    A local bus is described which is designed for use in a multi-chipcomposed microinstrumentation system. The bus is able to transmit a digital code, bitstream, analog voltage, frequency, duty-cycle and also provides calibration facilities, service request and interrupt request for the smart sensors. Corresponding sensor bus interface was implemented in a 1.6 m CMOS process and successfully tested in a local sensor network.Junta Nacional de Investigação Científica e Tecnológica - Praxis XXI-BD/5181/95. STW - Project DEL 55.3733. TUDelft
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