Clark T.-C. Nguyen

Bio: Clark T.-C. Nguyen is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Resonator & Q factor. The author has an hindex of 63, co-authored 218 publications receiving 12693 citations. Previous affiliations of Clark T.-C. Nguyen include University of Michigan & University of California.

MEMS technology for timing and frequency control

Abstract: An overview on the vise of microelectromechanical systems (MEMS) technologies for timing and frequency control is presented. In particular, micromechanical RF filters and reference oscillators based on recently demonstrated vibrating on-chip micromechanical resonators with Q's > 10,000 at 1.5 GHz are described as an attractive solution to the increasing count of RF components (e.g., filters) expected to be needed by future multiband, multimode wireless devices. With Q's this high in on-chip abundance, such devices might also enable a paradigm shift in the design of timing and frequency control functions, where the advantages of high-Q are emphasized, rather than suppressed (e.g., due to size and cost reasons), resulting in enhanced robustness and power savings. Indeed, as vibrating RF MEMS devices are perceived more as circuit building blocks than as stand-alone devices, and as the frequency processing circuits they enable become larger and more complex, the makings of an integrated micromechanical circuit technology begin to take shape, perhaps with a functional breadth not unlike that of integrated transistor circuits. With even more aggressive three-dimensional MEMS technologies, even higher on-chip Q's are possible, such as already achieved via chip-scale atomic physics packages, which so far have achieved Q's > 107 using atomic cells measuring only 10 mm3 in volume and consuming just 5 mW of power, all while still allowing atomic clock Allan deviations down to 10-11 at one hour

High-Q HF microelectromechanical filters

Abstract: IC-compatible microelectromechanical intermediate frequency filters using integrated resonators with Q's in the thousands to achieve filter Q's in the hundreds have been demonstrated using a polysilicon surface micromachining technology. These filters are composed of two clamped-clamped beam micromechanical resonators coupled by a soft flexural-mode mechanical spring. The center frequency of a given filter is determined by the resonance frequency of the constituent resonators, while the bandwidth is determined by the coupling spring dimensions and its location between the resonators. Quarter-wavelength coupling is required on this microscale to alleviate mass loading effects caused by similar resonator and coupler dimensions. Despite constraints arising from quarter-wavelength design, a range of percent bandwidths is still attainable by taking advantage of low-velocity spring attachment locations. A complete design procedure is presented in which electromechanical analogies are used to model the mechanical device via equivalent electrical circuits. Filter center frequencies around 8 MHz with Q's from 40 to 450 (i.e., percent bandwidths from 0.23 to 2.5%), associated insertion losses less than 2 dB, and spurious-free dynamic ranges around 78 dB are demonstrated using low-velocity designs with input and output termination resistances of the order of 12 k/spl Omega/.

Micromachined devices for wireless communications

Abstract: An overview of recent progress in the research and development of micromachined devices for use in wireless communication subsystems is presented. Among the specific devices described are tunable micromachined capacitors, integrated high-Q inductors, micromachined low-loss microwave and millimeter-wave filters, low-loss micromechanical switches, microscale vibrating mechanical resonators with Q's in the tens of thousands, and miniature antennas for millimeter-wave applications. Specific applications are reviewed for each of these components with emphasis on methods for miniaturization and performance enhancement of existing and further wireless transceivers.

An integrated CMOS micromechanical resonator high-Q oscillator

Abstract: A completely monolithic high-Q oscillator, fabricated via a combined CMOS plus surface micromachining technology, is described, for which the oscillation frequency is controlled by a polysilicon micromechanical resonator with the intent of achieving high stability. The operation and performance of micromechanical resonators are modeled, with emphasis on circuit and noise modeling of multiport resonators. A series resonant oscillator design is discussed that utilizes a unique, gain-controllable transresistance sustaining amplifier. We show that in the absence of an automatic level control loop, the closed-loop, steady-state oscillation amplitude of this oscillator depends strongly upon the dc-bias voltage applied to the capacitively driven and sensed /spl mu/resonator. Although the high-Q of the micromechanical resonator does contribute to improved oscillator stability, its limited power-handling ability outweighs the Q benefits and prevents this oscillator from achieving the high short-term stability normally expected of high-Q oscillators.

VHF free-free beam high-Q micromechanical resonators

Abstract: Free-free-beam flexural-mode micromechanical resonators utilizing nonintrusive supports to achieve measured Qs as high as 8400 at VHF frequencies from 30 to 90 MHz are demonstrated in a polysilicon surface micromachining technology. The microresonators feature torsional-mode support springs that effectively isolate the resonator beam from its anchors via quarter-wavelength impedance transformations, minimizing anchor dissipation and allowing these resonators to achieve high-Q with high stiffness in the VHF frequency range. The free-free-beam micromechanical resonators of this paper are shown to have an order of magnitude higher Q than clamped-clamped-beam versions with comparable stiffnesses.

Cavity Optomechanics

Abstract: We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Micromachined inertial sensors

Abstract: This paper presents a review of silicon micromachined accelerometers and gyroscopes. Following a brief introduction to their operating principles and specifications, various device structures, fabrication, technologies, device designs, packaging, and interface electronics issues, along with the present status in the commercialization of micromachined inertial sensors, are discussed. Inertial sensors have seen a steady improvement in their performance, and today, microaccelerometers can resolve accelerations in the micro-g range, while the performance of gyroscopes has improved by a factor of 10/spl times/ every two years during the past eight years. This impressive drive to higher performance, lower cost, greater functionality, higher levels of integration, and higher volume will continue as new fabrication, circuit, and packaging techniques are developed to meet the ever increasing demand for inertial sensors.

A tunable carbon nanotube electromechanical oscillator

Abstract: Nanoelectromechanical systems (NEMS) hold promise for a number of scientific and technological applications. In particular, NEMS oscillators have been proposed for use in ultrasensitive mass detection, radio-frequency signal processing, and as a model system for exploring quantum phenomena in macroscopic systems. Perhaps the ultimate material for these applications is a carbon nanotube. They are the stiffest material known, have low density, ultrasmall cross-sections and can be defect-free. Equally important, a nanotube can act as a transistor and thus may be able to sense its own motion. In spite of this great promise, a room-temperature, self-detecting nanotube oscillator has not been realized, although some progress has been made. Here we report the electrical actuation and detection of the guitar-string-like oscillation modes of doubly clamped nanotube oscillators. We show that the resonance frequency can be widely tuned and that the devices can be used to transduce very small forces.

Micro-electro-mechanical-systems (mems) and fluid flows

Abstract: The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electromechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research.