Thesis (M.Phil.)--City University of Hong Kong, 2005. / "Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Master of Philosophy" Includes bibliographical references (leaves 65-68)

Thesis (M.S. in Electrical Engineering)--University of California, Jan. 1955. / Includes bibliographical references.

Inaug.-diss.--Kiel. / Vita.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Rochester Institute of Technology, 2006. / Typescript. Includes bibliographical references (leaves 72-79).

In this work, the opto-piezo actuation and piezoelectric actuation in gallium arsenide (GaAs) is experimentally and theoretically verified. Experimentally the response of the respective actuations are measured using the current generated from the inverse piezoelectric effect. The mechanical structure used to generate this current is a micron size torsional resonator fabricated from a GaAs photodiode heterostructure. The photodiode heterostructure is optically and electrically designed as a photovoltaic (PV) cell while mechanically the structure resembles a bimorph. The bimorph design is a result of the PV cell consisting of a pn junction and a heterojunction where the depletion regions have the additional property of being piezoelectric. The opto-piezo actuation results from using the photogenerated voltage to piezoelectrically drive a mechanical structure. Using light modulated at the resonance frequency of the torsional resonator the measured current is shown to linearly increase with intensity. For the electrical actuation case, the torsional resonator is driven using the non- linear response of the pn junction to an applied voltage. The non-linear response results in generation of voltage at the harmonic frequencies of the applied voltage. The voltage generated at twice the applied frequency is given the label 2f and is used to piezoelectrically drive the mechanical structure. The above results for the two methods of actuation are theoretically validated by deriving a model for the expected current. The model predicts the current as a function of the voltage. For the opto-piezo case this voltage is the photovoltage. The photovoltage is determined using the AC PV model. This model is derived using the DC PV model and predicts the AC operation of a photodiode in the 3rd and 4th quadrants to resistive and reactive loads. Using the opto-mechanical coupling coefficient the efficiency of the opto-piezo actuation is compared to opto-thermal actuation and radiation pressure actuation. It is shown that the opto-piezo effect, in general, is several orders of magnitude better than the other two in converting optical energy into mechanical energy. This is an important result because in situations where low optical powers are only available and power, in general, cannot be spared, for e.g. on a satellite, devices that make use of the opto-piezo effect could be used for either actuation or sensing. Generally however, using the opto-piezo effect can lead to either integration of existing photonic devices with mechanical resonators or new photonic devices all together. For e.g. using the opto-piezo effect an adaptable optical correlator can be made which could be used to make artificial intelligent machines. / Thesis / Doctor of Philosophy (PhD)

SAW devices are known for their ability to withstand severe operating conditions. However, their data sheets generally provide very little information on their susceptibility to external factors other than temperature. In particular, no mention is made of their sensitivity to ionizing and non-ionizing radiation, even though they are being used in applications where such radiation is present. In this thesis, we report on experiments that we have conducted to measure the impact of intense gamma and neutron radiation on quartz SAW resonators. Packaged commercial 434 MHz quartz SAW resonators (RFM RP1308) were placed at the output of a Colbalt 60 source and exposed to gamma radiation of up to 50 Mrads. Additional devices were positioned in close proximity to the enriched uranium core of the McMaster University Nuclear Reactor and exposed to intense neutron radiation of 4.5 x 10^12 neutrons/cm^2s for up to 40 seconds. After waiting for a necessary cool-down period, the irradiated SAW resonators were placed in the feedback loop of a custom oscillator to measure the shift in output frequency as a function of radiation exposure. Small changes in the oscillator frequency of up to 15 ppm for the gamma radiation and of up to 10 ppm for neutron radiation were obtained in the experiments. However, no clear relationships were observed between the amount of radiation exposure and frequency shift in either case. / Thesis / Master of Applied Science (MASc)

The 21st century is emerging into an era of wireless ubiquity. To support this trend, the RF (Radio Frequency) front end must be capable of processing a range of wireless signals (cellular phone, data connectivity, broadcast TV, GPS positioning, etc.) spanning a total bandwidth of nearly 6 GHz. This warrants the need for multi-band/multi-mode radio architectures. For such architectures to satisfy the constraints on size, battery life, functionality and cost, the radio front-end must be made reconfigurable. RF-MEMS (RF Micro-Electro-Mechanical Systems) are seen as an enabling technology for such reconfigurable radios. RF-MEMS mainly include micromechanical switches (used in phase shifters, switched capacitor banks, impedance tuners etc.) and micromechanical resonators (used in tunable filters, oscillators, reference clocks etc.). MEMS technology also has the potential to be directly integrated into CMOS (Complementary metal-oxide semiconductor) ICs (Integrated Circuits) leading to further potential reductions of cost and size. However, RF-MEMS face challenges that must be addressed before they can gain widespread commercial acceptance. Relatively low switching speed, power handling, and high-voltage drive are some of the key issues in MEMS switches. Phase noise influenced by non-linearities, need for temperature compensation (especially Si based resonators), large start-up times, and aging are the key issues in Si MEMS Resonators. In this work potential solutions are proposed to address some of these key issues, specifically the reduction of high voltage drives in switches and the reduction of phase noise in MEMS resonators for timing applications. MEMS devices that are electrostatically actuated exhibit significant non-linearities. The origins of the non-linearities are both electrical (electrostatic actuation) and mechanical (dimensions and material properties). The influence of spring non-linearities (cubic and quadratic) on the performance of switches and resonators are studied. Gold electroplated fixed-fixed beams were fabricated to test the phenomenon of dynamic (or resonant) pull-in in shunt switches. The dynamic pull-in phenomenon was also tested on commercially fabricated lateral switches. It is shown that the resonant pull-in technique reduces the overall voltage required to actuate the switch. There is an additional reduction of total actuation voltage possible via applying an AC actuation signal at the correct non-linear resonant frequency. The demonstrated best case savings from operating at the non-linear resonanceis 50 % (for the lateral switch) and 60 % (for the vertical switch) as compared to 25 % and 40 % respectively using a fixed frequency approach. However, the timing response for resonant pull-in has been experimentally shown to be slower than the static actuation. To reduce the switching time, a shifted-frequency method is proposed where the excitation frequency is shifted up or down by a discrete amount 'Ω after a brief hold time. It was theoretically shown that the shifted-frequency method enables a minimum realizable switching time comparable to the static switching time for a given set of actuation frequencies. The influence of VDC on the effective non-linearities of a fixed-fixed beam is also studied. Based on the dimensions of the resonator and the type of resonance there is a certain VDC,Lin where the response is near linear (S ' 0). In the near-linear domain, the dynamic pull-in is the only upper bound to the amplitude of vibrations, and hence the amplitude of output current, thereby maximizing the power handling capacity of the resonator. Apart from maximizing the output current, it is essential to reduce the amplitude and phase variations of the displacement response which are due to noise mixing into frequency of interest, and are eventually manifested as output phase noise due to capacitive current nonlinearity. Two major aliasing schemes were analyzed and it was shown that the capacitive force non-linearity is the major source of mixing that causes the up-conversion of 1/f frequency into signal sidebands. The resonator's periodic response (displacement) is defined by a set of two first- order nonlinear ordinary differential equations that describe the modulation of amplitude and phase of the response. Frequency response curves of amplitude and frequency are determined from these modulation equations. The zero slope point on the amplitude resonance curve is the peak of the resonance curve where the phase ('dc) of the response is ±π/2. For a strongly non-linear system, the resonance curves are skewed based on the amount of total non-linearity S. For systems that are strongly non-linear, the best region to operate the resonator is the fixed point that correspond to infinite slope ('dc = ±2π/3) in the frequency response of the system. The best case phase noise response was analytically developed for such a fixed point. Theoretically at this fixed point, phase noise will have contributions only from 1/f noise and not from 1/f2 and 1/f3. The resonators phase can be set by controlling the rest of the phase in the loop such that the total phase around the loop is zero or 2π. In addition, this work has also developed an analytical model for a lateral MEMS switch fabricated in a commercial foundry that has the potential to be processed as MEMS on CMOS. This model accounts for trapezoidal cross sections of the electrodes and springs and also models electrostatic fringing as a function of the moving gap. The analytical model matches closely with the Finite Element (FEA) model. / Ph. D.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / According to the von Neumann-Landauer principle (VNL) for every bit of information lost during a computation, kT ln 2 amount of heat is dissipated into the environment. Irreversible logic, the basis of modern computing, inevitably leads to loss of information and is thus fundamentally bound by the VNL principle. However, its validity has been challenged since its inception and the case concerning its legitimacy is still open. Due to the tiny energy scales involved, this debate has been entirely academic in nature and an experimental test of the VNL principle is highly desired by both proponents and skeptics. Such a test would entail contrasting the energy dissipation of irreversible and reversible logic. In particular, we need to perform a non trivial logic both reversibly and irreversibly based on identical technology, testing whether or not energy dissipation for the reversible computation can be less than VNL limit while the irreversible computation is limited by the VNL limit. Reversible logic does not entail information loss, and hence is not bound by the VNL limit. It offers the potential for indefinite performance improvements of digital electronics. Bennett's Turing machine first proved that any computation can be performed reversibly and, in the proper limit, without energy cost. This promise of computing for free has spurred Fredkin, Toffoli, Wilczek, Feynman and others to propose reversible logic gates, though very few experimentally-realized reversible logic gates have since been reported. Here, we experimentally demonstrate for the first time the core of a logically reversible, CMOS-compatible, scalable nanoelectromechanical Fredkin gate, a universal logic gate from ... [TRUNCATED] / 2999-01-01