Abstract—Third-order, high-, micromechanical bandpass filters comprised of three ratioed folded-beam resonators coupled by flexural mode springs are demonstrated using an integrated circuit compatible, doped polycrystalline silicon surfacemicromachining technology. A complete design procedure for multiresonator micromechanical filters is presented and solidified via an example design. The use of quarter-wavelength coupling beams attached to resonators at velocity-controllable locations is shown to suppress passband distortion due to finite-mass and process mismatch nonidealities, which become increasingly important on this microscale. In addition, low-velocity coupling methods are shown to greatly alleviate the lithographic resolution required to achieve a given percent bandwidth. Ratioed foldedbeam micromechanical resonators are introduced as the key impedance transforming components that enable the needed low-velocity coupling. Using these design techniques, balanced three-resonator microscale mechanical filters with passband frequencies centered around 340 kHz are demonstrated with percent bandwidths of 0.1%, associated insertion losses as small as 0.1 dB, 20-dB shape factors as low as 1.5, and stopband rejections greater than 64 dB. Measurement and theory are rigorously compared and important limitations, such as thermal susceptibility, the need for passband tuning, and inadequate electromechanical coupling, are addressed. [470] Index Terms—Circuit modeling, fabrication, electromechanical coupling, filters, high-, insertion loss, MEMS, microelectromechanical devices, micromachining, micromechanical, passband

In parallel with the development of new technologies, new device configurations, and new applications for microsensors, microactuators, and microsystems, also referred to as microelectromechanical devices and systems (MEMS), there has arisen a growing need for computer-aided engineering and design systems. There is a wide range of design problems: process simulation, solid-body geometric renderings from photomasks and process descriptions, energetically correct simulation of behavior across multiple coupled energy domains, extraction of lumped low-order models of device behavior, optimization of geometry and process sequence, and design of full systems that include MEMS devices. Because of the computational demands of the modeling required to support full computer-aided design (CAD), there is a premium on fast and memory-efficient algorithms that help the designer, both by automating, where possible, complex sets of related tasks and by providing rapid computational prototyping at critical points in the design cycle. This paper presents an overview of the present state of the art in CAD for MEMS, with particular emphasis on the role of macromodels and test structures as part of the design environment. Keywords—CAD, design, macromodels, simulation, test structures. I.

In order to efficiently design complex microelectromechanical systems (MEMS) having large numbers of multi-domain components, a hierarchically structured design approach that is compatible with standard IC design is needed. A graphical-based schematic, or structural, view is presented as a geometrically intuitive way to represent MEMS as a set of interconnected lumpedparameter elements. An initial library focuses on suspended-MEMS technology from which inertial sensors and other mechanical mechanisms can be designed. The schematic representation has a simulation interface enabling the designer to simulate the design at the component level. Synthesis of MEMS cells for common topologies provides the system designer with rapid, optimized component layout and associated macro-models. A synthesis module is developed for the popular folded-flexure micromechanical resonator topology. The algorithm minimizes a combination of total layout area and voltage applied to the electromechanical actuators. Synthesis results clearly show the design limits of behavioral parameters such as resonant frequency for a fixed process technology.

Abstract — A completely monolithic high- 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 "resonator. Although the highof the micromechanical resonator does contribute to improved oscillator stability, its limited power-handling ability outweighs the benefits and prevents this oscillator from achieving the high short-term stability normally expected of high- oscillators. Index Terms — Fabrication, microelectromechanical devices, microelectromechanical systems (MEMS), micromachining, micromechanical, nonlinear oscillators, oscillators, oscillator stability, phase noise, resonators. I.

We are developing physical design tools for surfacemicromachined MEMS, such as polysilicon microstructures built using MCNC’s Multi-User MEMS Process service. Our initial efforts include automation of layout synthesis and behavioral simulation from a MEMS schematic representation. As an example, layout synthesis of a folded-flexure electrostatic combdrive microresonator is demonstrated. Lumpedparameter electromechanical models with two mechanical degrees-of-freedom link the physical and behavioral parameters of the microresonator. Simulated annealing is used to generate global optimized layouts of five different resonators from 3 kHz to 300 kHz starting with mixed-domain behavioral specifications and constraints. Development of the synthesis tool enforces codification of all relevant MEMS design variables and constraints. The synthesis approach allows a rapid exploration of MEMS design issues. 1.

Microresonator layouts are synthesized such that their preferred mode of oscillation is well-separated from the higher order in-plane and out-of-plane modes. Building on our previous work, we have incorporated models for four out-of-plane modes. All these modes are modeled as springmass systems. The spring constants and the effective masses of these modes are analytically derived. Synthesis is accomplished by encoding a design quality metric as the design objective while simultaneously constraining the design to meet user specifications. These constraints require that the resonant frequency in the preferred direction is sufficiently lower than (and, hence, dominates over) the resonant frequency of other modes of vibration of the structure. The models are verified by comparison with 3D FEM simulations and also with experimental measurements on fabricated resonators. The usefulness of these models is illustrated by comparing the oscillation modes of layouts synthesized with and without these models. This exercise also shows that such mode-separation can be achieved only if the microresonators have a structural thickness larger than flexure width.

Surface-micromachined comb-drive resonators suspended by meander springs are modelled and simulated. General analytic expressions for lateral spring constants and effective mass of meander springs are derived and verified by finiteelement simulations. The spring constant equations are accurate to within 1% over a wide range of geometries. Analytic, simulated, and measured resonant frequency values agree to within 0.3 % for each of ten different microresonator designs. 1

I thank my advisor Dr. Tamal Mukherjee for his constant guidance and encouragement. I am also thankful to Prof. Gary Fedder for his useful suggestions in a number of aspects of the work. I thank Steve Eagle for releasing the fabricated devices, Hasnain Lakdawala for help with the measurements and all the other students in the MEMS research group for stimulating discussions from time to time. elsewhere. I also acknowledge the invaluable support of my family and my friends in Pittsburgh and

Monolithic RF circuits capable of operating over multiple frequency bands are highly desired due to popular demand for low cost and compact multiband radios. This thesis presents designs of one such RF circuit called LNA. The presented LNAs are frequency reconfigurable tuned amplifiers i.e. they are narrow band circuits whose frequency of operation can be dynamically changed. The frequency reconfigurability is achieved by the use of monolithic CMOS-MEMS passives. In this thesis all the possible configurations obtained by adding a single varactor to the input and the output of an emitter degenerated cascode LNA core has been analyzed. Low noise, low power, input match, frequency reconfigurability, and monolithic implementation were the main constraints to determine the acceptability of an configuration. Three acceptable configurations have been identified and circuit designs based on these configurations has been presented. Circuits have been designed using a methodology developed during this work. The methodology designs for good noise and power matching at the input, over the entire frequency range of operation, and under a DC power constraint.