1,046 research outputs found
Novel Design of a RF-MEMS Tuneable Capacitor Based on Electrostatically Induced Torsion
No full textMicro-Electro-Mechanical System (MEMS) RF switches have been one of the most interesting areas for research and development in the last years. It has been shown that they have an excellent performance in the RF and microwave frequency range and a great effort has been dedicated in designing suitable geometries and structures best suited for switching application. In parallel other devices useful for the construction of complex RF circuits have been proposed and studied. Among these tuneable capacitors are of high interest for a variety of applications. In this paper we present a new electromechanical design for a tuneable capacitor with a totally different shape from usual designs. In particular we try to exploit the effect of the small in-plane force that develops during the polarization of a parallel plate capacitor with partially overlapping plates. First prototype realizations are discussed and analyzed and as the first realization showed some problems an improved design is presented
TOPOLOGY OPTIMIZATION OF REINFORCED POLYSILICON
No full textThe sensitivity of a silicon condenser microphone, which essentially consists of a rigid backplate and a thin movable diaphragm, mainly depends on diaphragm performance. There is the possibility to use diaphragms working either in a membrane or in a plate mode, with tensile forces or bending forces governing the sensitivity to sound pressure respectively. In this study, the numerical simulation of a reinforced polysilicon thin plate is conducted in order to optimize the overall performance of a MEMS condenser microphone. The geometrically nonlinear finite-element method is adopted to analyze the mechanical sensitivity of the diaphragm, and stress stiffening is included in the analysis since the out-of-plane stiffness of the diaphragm can be drastically affected by the state of in-plane residual stresses [1]. The influence on the diaphragm performance of reinforcement parameters and the material residual stresses are studied, and optimum geometric designs are determined to accomplish a range of microphone specifications
A General Purpose Reconfigurable MEMS-Based Attenuator for Radio Frequency and Microwave Applications
No full textIn this paper we present a power attenuator for RF (RadioFrequency) and microwave signals entirely designed in MEMS (MicroElectroMechanical-System) technology. It is fabricated in the RF-MEMS technology available at Fondazione Bruno Kessler (FBK) based on a surface micromachining process. The network is realized in a low-cost manufacturing process and its dimensions are significantly compact compared to traditional implementations of RF power attenuators. More interestingly, employment of MEMS technology for such architecture enables a very large reconfigurability, making the network compatible with different standards and usable in several wireless communication systems. Electromechanical and RF behaviour of the discussed network are simulated and compared against experimental results collected by the first fabricated samples. RF measured performances are rather promising in spite a technology issue occurred during the fabrication deteriorating the attenuator low-frequency characteristic. RF modelling of such issue (already fixed in the batches being currently fabricated) is shown and discussed through this paper
A simple analytical method for residual stress measurement on suspended MEM structures using surface profilometry
No full textThis paper presents an analytical method to calculate residual stress and Young’s modulus in clamped-clamped beams. These types of structures are a typical building block of many MEMS devices, and this guarantees an accurate transferability of the measured parameters. The method is based on the determination of beam bending as a function of applied load by means of a surface profiler, and as a function of beam length. By modeling analytically both the elastic and the stress contribution to beam bending, it is possible to obtain both the stress value and the Young’s modulus by a simple fitting of the experimental data. Results are presented for electrodeposited gold beam arrays of different width, but the method is in principle exploitable for every type of suspended film where the residual stress strongly influences the material properties. Accuracy and limitations of the method are also discussed
Investigation methods and approaches for alleviating charge trapping phenomena in ohmic RF-MEMS switches submitted to cycling test
No full textWe propose and discuss a detailed reliability investigation of ohmic RF-MEMS switches, affected by high
charge trapping phenomena, and we analyse how these test methods affect the study of charge trapping
issues. We investigate the effect of three different parameters that have to be considered when cycling
ohmic RF-MEMS switches. In particular the effect of the shape of the actuation pulse, the cycling frequency
and the RF input power are analysed. Our experimental investigations show interesting trends
and results that might help the analysis of ohmic RF-MEMS switches during cycling tests. These
approaches, in fact, suggest how to better control and to reduce the charge trapping effect maximizing
the lifetime of RF-MEMS switches
Serine-Threonine protein kinases CK1, CK2 and GSK3 in normal and malignant haematopoiesis
No full textFrequency and Bandwidth Control of Switchable Microstrip Bandpass Filters using RF-MEMS Ohmic Switches
No full textIn this paper a reconfigurable bandpass filter is designed using ohmic-contact cantilever-type Micro Electro Mechanical Systems (MEMS)switches. The filter can switch between two different states with a center frequency tunable range of 13% in C band. The topology allows achieving two accurate center frequencies, each associated with a precisely defined bandwidth, using six MEMS ohmic-switches. The design carefully takes into account the external quality factor for both filter states to ensure a good impedance match at each frequency. The two sets of coupling coefficients and resonator lengths implemented with the MEMS ohmic switches originate the bandwidths and center frequencies required by design specifications. The filter is designed to have center frequencies of 5.5 and 6.2 GHz, with a fractional bandwidth (FBW) of 5 and 3%, respectively. Filter specifications were successfully met with the proposed topology. The filter was fabricated on a quartz substrate and measured responses are in good agreement with simulations
Exposure-Tolerant Imaging Solution forCultural Heritage Monitoring
No full textThis paper describes a simple and cheap solution specifically designed for monitoring the degradation of thin coatings employed for metal protection. The proposed solution employs a commercial photocamera and a frequency-domain-based approach that is capable of highlighting the surface uniformity changes due to initial corrosion. Even though the proposed solution is specifically designed to monitor the long-time performance of protective coatings employed for the restoration of silver artifacts, it can be successfully used also for assessing the conservation state of other ancient metallic works of art. The proposed solution is made tolerant to exposure changes by using a procedure for sensor nonlinearity identification and correction, does not require a precise lighting control, and employs only free open-source software, so that its overall cost is very low and can be used also by not specifically trained operator
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