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Beneficial effect of diffraction on the frequency response of a 250-MHz SAW mobile IF resonator-filter with long IDTs and triple longitudinal modes on quartz

Beneficial effect of diffraction on the frequency response o...

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IEEE Symposium (IUS) Ultrasonics

作者： C.K. Campbell Department of Electrical& Computer Engineering McMaster University Hamilton ONT Canada

Diffraction theory is applied to model the frequency response of a low-loss (/spl sim/2 dB) 250-MHz SAW mobile IF resonator-filter (BW /spl sim/0.2%) with long-pair IDTs and triple longitudinal modes on ST-quartz, as applicable to circuitry such as for the Japanese Personal Handy Phone (PHP). In a simplified approach, a parabolic diffraction approximation is applied, with the IDT acoustic aperture conceptually sub-divided into parallel channel strips of equal widths. An anisotropy parameter value A/sub d/=-0.22 for ST-quartz is used in the parabolic approximation. Frequency responses of individual segments are summed, using quadratically-shifted wave vector values in the parabolic diffraction approximation, together with Fraunhofer and phase corrections. Excellent agreement is obtained between theory and reported experimental frequency responses.

关键词： Frequency response Surface acoustic waves Acoustic diffraction Resonator filters Resonance Bandwidth Optical reflection Fingers Apertures Anisotropic magnetoresistance

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Observer design for non-integrable systems

Observer design for non-integrable systems

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American Control Conference (ACC)

作者： A.F. Lynch S.A. Bortoff Department of Electrical& Computer Engineering University of Toronto Toronto ONT Canada

Systems for which no observer with linear error dynamics exists are termed nonintegrable. Generically, nonlinear systems are nonintegrable. Using results developed for approximate feedback linearization, we propose two approaches to observer design for nonintegrable, unforced, single-output systems. An example illustrates the design procedure.

关键词： Observers Feedback Linear approximation Nonlinear systems Control systems Ear Systems engineering and theory Councils Distributed computing State estimation

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Direction finding via joint diagonalization

Direction finding via joint diagonalization

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IEEE Workshop on Statistical Signal and Array Processing

作者： A.J. Weiss B. Friedlander Department Electrical Engineering Systems Tel-Aviv University Tel-Aviv Israel Department Electrical& Computer Engineering University of California Davis CA USA

An approach to array processing (i.e., direction finding, signal separation and reconstruction, and calibration) based on the analytical constant modulus algorithm is considered. The main advantage of this approach is that the multidimensional search associated with maximum likelihood based estimators or the single dimensional search associated with MUSIC type methods are eliminated. The sensor array elements are assumed to have the same, up to a multiplicative constant, angle dependent, unknown gain pattern. We show that under this assumption it is possible to estimate the array response matrix and then use the result for direction finding, if the nominal array manifold is known, at least approximately. It is also possible to use the estimated array response matrix in order to separate and reconstruct the signals, or calibrate the array shape or response.

关键词： Sensor arrays Array signal processing Source separation Calibration Signal analysis Algorithm design and analysis Multidimensional systems Maximum likelihood estimation Multiple signal classification Shape

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Performance of antenna arrays with fading signals

Performance of antenna arrays with fading signals

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Asilomar Conference on Signals, Systems & computers

作者： A.J. Weiss B. Friedlander Department Electrical Engineering -Systems Tel-Aviv University Tel-Aviv Israel Department Electrical& Computer Engineering University of California Davis CA USA

We study the effect of fading on estimating the antenna array response, and subsequently separating and estimating the unknown data streams. The results are presented in the form of output signal to interference ratio (SIR) and output signal to noise ratio (SNR). We obtain closed form expressions for the average output SNR and SIR for Rayleigh, Rician and Nagakami fading. It is shown that in the presence of slowly fading channels, the diversity advantage of the array decreases as the number of signals increases.

关键词： Antenna arrays Fading Rayleigh channels Signal to noise ratio Interference Signal processing Sensor arrays Mobile communication Frequency Tracking

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An investigation of an adaptive modeling algorithm for magnetic resonance image reconstruction

An investigation of an adaptive modeling algorithm for magne...

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IEEE Pacific Rim Conference on Communications, computers and Signal Processing

作者： J. Yang M.R. Smith S.T. Nichols Department of Electrical& Computer Engineering University of Calgary AB Canada Department of Electrical &Computer Engineering University of Calgary AB Canada Department of Electrical & Computer Engineering University of Calgary AB Canada

For estimating the AR (autoregressive) parameters from nonstationary MR (magnetic resonance) data, the authors introduce an algorithm with an adaptive mechanism, which attempts to follow the statistical variation of the data. Medical and material MR images reconstructed using the LSL (least-squares lattice) algorithm were more stable than the original nonadaptive TERA (transient error reconstruction algorithm) ARMA (autoregressive moving average) modeling algorithm. Stability with that algorithm was obtained by using several ad-hoc methods which did not make best use of the available resolution achieved by using modeling. Stability with the LSL algorithm was obtained by its adaptive characteristics to allow it to follow the varying properties.< >

关键词： Magnetic resonance Image reconstruction Autoregressive processes Magnetic resonance imaging Discrete Fourier transforms Least squares methods Image resolution Diseases Reconstruction algorithms Error correction

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Including anisotropy in electrical impedance tomography using anatomical constraints

Including anisotropy in electrical impedance tomography usin...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： M.E. Glidewell K.T. Ng Electrical& Computer Engineering Department New Mexico State University Las Cruces NM USA

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A microprocessor controlled drive for 3-phase permanent magnet brushless DC motor

A microprocessor controlled drive for 3-phase permanent magn...

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Power Conversion Conference

作者： G. Maani M.A. Rahman W.J. Bonwick G.L. Seet Department of Electrical& Electrical Engineering Nanyang Technological University Singapore Department of Electrical Engineering Memorial University of Newfoundland Saint John's NEW Canada Department of Electrical & Computer System Engineering Monash University Clayton VIC Australia

This paper deals with various PWM switching techniques for driving a 3-phase brushless DC motor. The analog based natural and microprocessor based regular PWM sampling schemes are presented. The 3-level PWM scheme is considered since it offers an improved quality supply and reduced harmonic spectra. The response of the PM motor to these various driving schemes is assessed.< >

关键词： Microprocessors Brushless DC motors Pulse width modulation Space vector pulse width modulation Voltage DC motors Sampling methods Pulse width modulation inverters Bridge circuits Stators

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Inverter topologies and control techniques for sinusoidal output power supplies

Inverter topologies and control techniques for sinusoidal ou...

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Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC)

作者： D.M. Divan Department of Electrical& Computer Engineering University of Wisconsin Madison Madison WI USA

The author reviews the state of the art in terms of power converter topologies and control techniques for realizing sinusoidal output systems. In terms of control strategy, the use of a variety of pulsewidth modulation (PWM) techniques have been proposed for realizing small filter size and good spectral performance. Some of the more popular techniques prevalent in industry are of potential importance and are reviewed. Alternatives for single and polyphase systems are examined. A variety of topologies are seen to be suitable, including conventional PWM inverters, soft switching resonant link inverters, and high-frequency AC link converters. Control strategies which yield output waveforms with good spectral purity, particularly in the presence of nonlinear loads, are examined. Both voltage and current regulator based controllers are seen to be viable alternatives.< >

关键词： Topology Pulse width modulation Pulse width modulation inverters Control systems Size control Space vector pulse width modulation Filters electrical equipment industry Resonance Switching converters

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3-DIMENSIONAL RAY THEORY OF ASTIGMATIC BRAGG-DIFFRACTION IMAGE-FORMATION WITH ANASTIGMATIC ILLUMINATION

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APPLIED OPTICS 1989年第20期28卷 4353-4359页

作者： KORPEL, A MEHRL, DJ The authors are with University of Iowa Department of Electrical& Computer Engineering Iowa City Iowa 52242

We analyze and demonstrate Bragg diffraction imaging with convenient anastigmatic(e.g., spherical) illumination and find that this technique results inseparately located horizontal and vertical images of the sound field withdifferent magnification and resolution. Results of physical experiments showgood agreement with theory and demonstrate that the insertion of one relativelyweak cylinder lens makes the images coincide.

关键词： Acoustooptic modulators Cylindrical lenses Diffraction Image processing Light propagation Ray tracing

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Optically tuned patch antenna for phased array applications

Optically tuned patch antenna for phased array applications

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Antennas and Propagation Society International Symposium

作者： A. Daryoush K. Bontzos P. Herczfeld Department Electrical& Computer Engineering Drexel University Philadelphia PA USA

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