High quality tunable MEMS parallel plate capacitors have been widely used in phase shifters, oscillators and tunable
filters for wireless communication. As electrostatic actuation and air dielectrics have led to devices with low power
consumption and high quality factors, an electrostatically actuated MEMS tunable capacitor with two flexible plates have
been designed and fabricated in this paper. According to the measurement results, tunable capacitor shows good
performance in the frequency range of 2GHz-10GHz. The pull-in voltage for the capacitor is 13 V. The tuning ratio of
the capacitor is very high, which can reach 320%.
As part of an effort to develop MEMS-based power generation system, an assembly solution for combustion test of a recent-developed micro combustion device micromachined from single crystal silicon were proposed. In order to supply hydrogen/air to inlets of micro combustor from room temperature to over 700°C at the pressure of 1~3bars, a stainless steel universal fixture was designed and fabricated for the combustion testing of prototype stacked by structured Si wafers of 21.5mmx21.5mm in square. By precisely welding and polishing process in fabrication of the fixture, a metal plate with 18nm roughness was prepared for tightly connecting micro combuster with fuel inlet of 2mm, air inlet 4mm in diameter on the top wafer, while the gap between tubings to be hermetically joined to top plate is about 0.3mm. Primary combustion experiments have been conducted after igniting the fuel/air mixture in the micro chamber. Stable hydrogen-air combustion has been observed to sustain inside the combustion chamber with exit temperature over 1200°C. During the combustion experiments, the silicon dies keep good mechanical integrity under assembly and no gas leakage is observed.
In this paper, RF MEMS capacitive switch with a novel metal/dielectric (Au/SiN) composite beam on highly resistive silicon substrate is presented. The low-stress SiN under the Au electrode layer is adopted due to its excellent dielectric and mechanical characteristic. Four beam structures are designed, and mechanical/electrostatic and high frequency analysis tools are used to explore their performance. It can be seen from the analysis that satisfying switching property can be obtained from careful choice and optimization of the structure. Besides, the switch has shown excellent radio frequency (RF) performance. In addition, the composite beam, which is stiffer than pure metal ones, may not only provide good DC insulation and RF isolation augmentation but also theoretically help to reduce the danger of beam stiction. With different structures, this switch can meet the requirement of a wide variety ofhigh frequency applications. These features made this micro switch an optimal solution for mobile or fixed RF applications, such as in the construction of millimeter wave phase shifter MMIC and switched tunable filters, for wireless telecommunication or radar use.
A micromachined tunable RF capacitor with interdigitated comb plate structure is investigated in this paper. Much effort to improve tuning ratio, such as minimizing parasitical capacitance, is presented. Analysis shows the bias voltage can be lowered through the optimization of the structure parameters. Also presented is the fabrication of this capacitor based on typical bulk silicon micromachining technology.
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