Lifetime characterization of capacitive power RF MEMS switches

RF MEMS switches provide a low-cost,high performance solution to many RF/microwaveapplications and these switches will be importantbuilding blocks for designing phase shifters, switchedfilters and reflector array antennas for military andcommercial markets.In this paper, progress in characterizing of THALEScapacitive MEMS devices under high RF power ispresented. The design, fabrication and testing ofcapacitive RF MEMS switches for microwave/mm- waveapplications on high-resistivity silicon substrate ispresented .The switches tested demonstrated powerhandling capabilities of 1W (30 dbm) for continuous RFpower. The reliability of these switches was tested atvarious power levels indicating that under continuousRF power. In addition a description of the powerfailures and their associated operating conditions ispresentedThe PC-based test stations to cycle switches and measurelifetime under DC and RF loads have been developed.Best-case lifetimes of 1010 cycles have been achieved inseveral switches from different lots under 30 dbm RFpower

Modélisation, conception et caractérisation d'un commutateur hyperfréquence à base de nanotubes de carbone verticaux

Depuis leur découverte, les propriétés des nanotubes de carbones ont largement été étudiées. L étude de la pertinence scientifique et de la faisabilité d un commutateur NEMS RF ohmique et capacitif constitue un axe de recherche dont les résultats seraient susceptibles d être supérieurs aux performances des MEMS RF. Il existe trois géométries de commutateurs, la poutre, le pont et la pince. Cette thèse propose une étude approfondie d un NEMS RF en configuration pince par une explication détaillée de l ensemble des étapes de dimensionnement, de fabrication et de caractérisation. Une recherche bibliographique a défini les éléments théoriques indispensables à la maîtrise et à la cohérence de cette démarche scientifique. Différentes expérimentations en croissance de nanotubes de carbone par la méthode PECVD sur un empilement de différents matériaux susceptibles de composer le NEMS ont été réalisées pour aboutir à une structure répondant aux exigences physiques d un NEMS RF et à la contrainte thermique de synthèse PECVD (600C à 800C). Les expérimentations effectuées en commutation sur des commutateurs NEMS illustrent la réalisation et le fonctionnement de ces structures. Les résultats encourageants en simulation hyperfréquence et la faisabilité de NEMS RF apportent une crédibilité à la poursuite de ces travaux, avec pour objectif, des mesures expérimentales en hyperfréquence confirmant ou infirmant les modèles théoriques et les simulations.Since their discovery, the properties of carbon nanotubes have been widely studied. The study of scientific relevance and feasibility of an ohmic and capacitive RF NEMS represents an area of research whose results would likely exceed the performances of RF MEMS. There are three switch designs, the cantilever, the bridge and the tweezer. This thesis offers a comprehensive study of RF NEMS switch in a tweezer configuration with a detailed explanation of all phases of modelization, fabrication and characterization. A literature search set the necessary theoretical elements for the knowledge and the consistency of this scientific process. Various experiments on the carbon nanotubes growth by PECVD method on a stack of different materials likely to compose the NEMS have been realized to result in a structure meeting the physical specifications of a NEMS RF and the thermal stress in PECVD synthesis (600C to 800C). The commutation experiments carried out on the NEMS switch illustrate the fabrication and the operation of these structures. The encouraging results in high frequency simulation and the fabrication of RF NEMS have brought credibility to the continuation of this work, with the objective of experimental measurements at high frequency in order to confirm or refute the theoretical models and the software simulations.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Experimental Microwave Complex Conductivity Extraction of Vertically Aligned MWCNT Bundles for Microwave Subwavelength Antenna Design

International audienceThis paper reports the extraction of electrical impedance at microwave frequencies of vertically aligned multi-wall carbon nanotubes (VA MWCNT) bundles/forests grown on a silicon substrate. Dedicated resonating devices were designed for antenna application, operating around 10 GHz and benefiting from natural inductive/capacitive behavior or complex conductivity in the microwave domain. As obtained from S-parameters measurements, the capacitive and inductive behaviors of VA MWCNT bundles were deduced from device frequency resonance shift

Reducing Cardiac Steatosis: Interventions to Improve Diastolic Function: A Narrative Review

Heart failure is one of the main causes of morbidity and mortality around the globe. Heart failure with preserved ejection fraction is primarily caused by diastolic dysfunction. Adipose tissue deposition in the heart has been previously explained in the pathogenesis of diastolic dysfunction. In this article, we aim to discuss the potential interventions that can reduce the risk of diastolic dysfunction by reducing cardiac adipose tissue. A healthy diet with reduced dietary fat content can reduce visceral adiposity and improve diastolic function. Aerobic and resistance exercises also reduce visceral and epicardial fat and ameliorate diastolic dysfunction. Some medications, include metformin, glucagon-like peptide-1 analogues, dipeptidyl peptidase-4 inhibitors, thiazolidinediones, sodium-glucose co-transporter-2, inhibitors, statins, ACE-Is, and ARBs, have shown different degrees of effectiveness in improving cardiac steatosis and diastolic function. Bariatric surgery has also shown promising results in this field

Thermal Reliability Study of Polymer Bonded Carbon Nanotube Array Thermal Interface Materials

Following Moores law, the development of electronics has led to an exponential increase of transistor density over the last couple of decades. Unfortunately, this trend also gives an increased heat power density in active components. Thermal interface materials (TIMs) are used to decrease the thermal resistance in thermal packages by filling out air gaps that naturally form there. TIMs are at the same time identified as a bottleneck due to their relatively low thermal conductivity. Carbon nanotubes (CNTs) are proposed as a future material for TIMs due to their high thermal conductivity and conformable nature. However, no reliability studies for CNT array TIMs can be found in literature that would demonstrate how these types of interfaces would perform. This is to the authors best knowledge the first reported study on thermal reliability for a CNT array TIM, which will be an important step towards a market realisation