Zhang H.,University of North Texas |
Kosinski J.,Monmouth University |
Kosinski J.,MacAulay Brown Inc.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2012
The free vibrations of a two-layered C-axis inclined zig-zag ZnO thin-film bulk acoustic wave resonator (FBAR) connected to external impedance are analyzed. The frequency equation and mode shape for this resonator are derived based on the linear piezoelectric theory. The impedance characteristics of the FBAR are derived and compared with previous experimental results. © 2012 IEEE.
Zhang H.,University of North Texas |
Kosinski J.,Monmouth University |
Kosinski J.,Macaulay Brown Inc.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2013
Stress-induced surface acoustic wave velocity shifts are analyzed for langasite (LGS) SAW resonators. The analytical methodology has been verified by comparing experimental results and analytical results for quartz resonators. LGS SAW resonators with Euler angles which are most sensitive and least sensitive to diametrical forces are determined and their applications in force sensors and resonators with minimum acceleration sensitivity are discussed. Sensitivity of the analytical results to different groups of nonlinear material constants is discussed; it was found that for specific configurations, failure to include the third-order piezoelectric constants, dielectric constants and electrostrictive constants may lead to a significant calculation error. Surface acoustic waves propagating on an LGS square plate subject to bending moment along the propagation direction and normal to the propagation direction are analyzed; it was found that the average momentinduced velocity shift of LGS resonators are comparable to quartz resonators. Analyses of the sensitivity of the results to different groups of nonlinear material constants shows that for some specific wave propagation directions, failure to include the third-order piezoelectric constants, dielectric constants, and electrostrictive constants may lead to large errors. © 1986-2012 IEEE.
Zhang H.,University of North Texas |
Kosinski J.A.,MacAulay Brown Inc. |
Zuo L.,Virginia Polytechnic Institute and State University
Ultrasonics | Year: 2016
In this paper, we examine the significance of the various higher-order effects regarding calculating temperature behavior from a set of material constants and their temperature coefficients. Temperature-induced velocity shifts have been calculated for quartz surface acoustic wave (SAW) resonators and the contributions of different groups of nonlinear material constants (third-order elastic constants (TOE), third-order piezoelectric constants (TOP), third-order dielectric constants (TOD) and electrostrictive constants (EL)) to the temperature-induced velocity shifts have been analyzed. The analytical methodology has been verified through the comparison of experimental and analytical results for quartz resonators. In general, the third-order elastic constants were found to contribute most significantly to the temperature-induced shifts in the SAW velocity. The contributions from the third-order dielectric constants and electrostrictive constants were found to be negligible. For some specific cases, the third-order piezoelectric constants were found to make a significant contribution to the temperature-induced shifts. The significance of each third-order elastic constant as a contributor to the temperature-velocity effect was analyzed by applying a 10% variation to each of the third-order elastic constants separately. Additionally, we have considered the issues arising from the commonly used thermoelastic expansions that provide a good but not exact description of the temperature effects on frequency in piezoelectric resonators as these commonly used expansions do not include the effects of higher-order material constants. © 2016
Horvath M.S.,MacAulay Brown Inc. |
Gorham L.A.,Air Force Research Lab |
Rigling B.D.,Wright State University
IEEE Transactions on Aerospace and Electronic Systems | Year: 2013
The polar format algorithm (PFA) for synthetic aperture radar (SAR) image formation utilizes a first-order Taylor approximation of the differential range to improve computational efficiency, leading to image distortion and defocus. Limiting scene size by bounding the second-order Taylor series terms can restrict the impact of these errors, or alternatively, one may correct for these errors through spatially-variant filtering in post processing. In this letter we analyze the increase in allowable scene size that is realized through such processing. © 1965-2011 IEEE.
He H.,University of Nebraska - Lincoln |
Yang J.,University of Nebraska - Lincoln |
Kosinski J.A.,MacAulay Brown Inc.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2015
We perform a theoretical analysis of the secondorder in-plane acceleration sensitivity of a Y-cut quartz thickness-shear mode resonator. The second-order nonlinear theory of elasticity for anisotropic crystals is used to determine the biasing fields in the resonator under in-plane acceleration. The acceleration-induced frequency shift is determined from a perturbation analysis based on the plate equations for small-amplitude vibrations superposed on a finite bias. We show that, whereas the first-order acceleration-induced frequency shift is zero for a structurally symmetric resonator under in-plane acceleration, the second-order frequency shift is nonzero and is quadratic in the acceleration. As the fourth-order nonlinear elastic constants of quartz have never been measured, we can only estimate the magnitude of the second-order frequency shift. For a particular case of interest, we find Δω/ω0~10-18, 10-16, and 10-14 when the acceleration is 1, 10, and 100 g, respectively. © 1986-2012 IEEE.
Riasati V.,MacAulay Brown Inc. |
Srinivas U.,Pennsylvania State University |
Monga V.,Pennsylvania State University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012
The set of orthogonal eigen-vectors built via principal component analysis (PCA), while very effective for com- pression, can often lead to loss of crucial discriminative information in signals. In this work, we build a new basis set using synthetic aperture radar (SAR) target images via non-negative matrix approximations (NNMAs). Owing to the underlying physics, we expect a non-negative basis and an accompanying non-negative coecient set to be a more accurate generative model for SAR proles than the PCA basis which lacks direct physical interpretation. The NNMA basis vectors while not orthogonal capture discriminative local components of SAR target images. We test the merits of the NNMA basis representation for the problem of automatic target recognition using SAR images with a support vector machine (SVM) classier. Experiments on the benchmark MSTAR database reveal the merits of basis selection techniques that can model imaging physics more closely and can capture inter-class variability, in addition to identifying a trade-off between classication performance and availability of training. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Rigling B.D.,Wright State University |
Roush C.,MacAulay Brown Inc.
IEEE National Radar Conference - Proceedings | Year: 2010
Classification of radar waveform phase modulation based on a sequence of observations is a simple problem complicated by a number of nuisance parameters. Without prior knowledge of waveform carrier frequency, time offset, amplitude, initial phase, and bandwidth, application of a matched filter classifier is not achievable. One must instead rely on waveform features that are invariant to these parameters. This paper presents an invariant feature set for waveform classification. Testing of these features on simulated radar waveforms has illustrated the desired invariance properties and robustness to low signal-to-noise ratio. © 2010 IEEE.
Hall D.C.,MacAulay Brown Inc.
Systems Engineering | Year: 2011
Many of the objections to implementing Risk Management and acting upon risk results hinge on the subjectivity of the risk assessment system. This subjectivity makes it difficult to make risk assessments justifiable, repeatable, and comparable over an entire project, program, or organization. One cannot easily justify assigning a 30% likelihood to a risk occurring when others with more, the same, or less experience are ascribing a 60% likelihood of occurrence to a similar risk. How to get all (or most) risk assessments, regardless of type (software, hardware, integration, programmatic, external, etc.), justifiable, repeatable, and comparable has been one of the holy grails of Risk Management for years. The methodology outlined in this paper meets at least some of this requirement. The methodology requires incorporating the Likelihood of Occurrence into a set of specifically defined sublevels under each risk category rather than using it as a separate multiplication factor. Basically, the assumption behind this methodology is that the more mature the process, the more experience available, the more detailed the design, etc., the lower the likelihood of occurrence of a specific risk becomes. Making this assumption, incorporating the likelihood into each specific sublevel and requiring justification for each choice then allows the establishment of more representative scores for project risks and allows risk information to be presented in a justifiable, repeatable, and comparable fashion. Copyright © 2010 Wiley Periodicals, Inc.
MacAulay Brown Inc. | Date: 2013-10-10
According to one embodiment, the present invention includes a method for numerically encoding and representing data that includes providing a representation of data and separating the representation into a scale header and an additional precision packet. Separating the representation includes identifying the location of the highest-order non-zero bit and encoding the location of the highest-order non-zero bit to form the scale header. The balance of the bits following the highest-order non-zero bit, or a truncated set of these bits, is encoded to form the additional precision packet, and a matched representation space (MRS) representation is composed of the paired data structures of a scale header and a corresponding additional precision packet, if any.
MacAulay Brown Inc. | Date: 2014-11-21
A method and apparatus for low voltage conversion and energy storage uses a charge pump array including a first set of capacitors in parallel with a second set of capacitors and switches for selectively coupling the first and second set of capacitors to a variable input DC voltage. A data processor programmably controls one or more of the switches to couple the first and second set of capacitors to the variable input DC voltage for a variable first time period during which the input DC voltage charges the first and second set of capacitors to a DC voltage level. An energy storage device is switchably coupled to an output of the charge pump array. The data processor programmably controls one or more of the switches to couple the charge pump array output to the energy storage device for a variable second time period during which a voltage stored across each of the capacitors during the first time period is combined to produce a higher voltage significantly higher than the input DC voltage, the higher voltage being provided to the energy storage device.