Showing papers on "Filter (video) published in 2001"

Design and control of an LCL-filter-based three-phase active rectifier

Abstract: This paper proposes a step-by-step procedure for designing the LCL filter of a front-end three-phase active rectifier. The primary goal is to reduce the switching frequency ripple at a reasonable cost, while at the same time achieving a high-performance front-end rectifier (as characterized by a rapid dynamic response and good stability margin). An example LCL filter design is reported and a filter has been built and tested using the values obtained from this design. The experimental results demonstrate the performance of the design procedure both for the LCL filter and for the rectifier controller. The system is stable and the grid current harmonic content is low both in the lowand high-frequency ranges. Moreover, the good agreement that was obtained between simulation and experimental results validates the proposed approach. Hence, the design procedure and the simulation model provide a powerful tool to design an LCL-filter-based active rectifier while avoiding trial-and-error procedures that can result in having to build several filter prototypes.

A Sequential Ensemble Kalman Filter for Atmospheric Data Assimilation

Abstract: An ensemble Kalman filter may be considered for the 4D assimilation of atmospheric data. In this paper, an efficient implementation of the analysis step of the filter is proposed. It employs a Schur (elementwise) product of the covariances of the background error calculated from the ensemble and a correlation function having local support to filter the small (and noisy) background-error covariances associated with remote observations. To solve the Kalman filter equations, the observations are organized into batches that are assimilated sequentially. For each batch, a Cholesky decomposition method is used to solve the system of linear equations. The ensemble of background fields is updated at each step of the sequential algorithm and, as more and more batches of observations are assimilated, evolves to eventually become the ensemble of analysis fields. A prototype sequential filter has been developed. Experiments are performed with a simulated observational network consisting of 542 radiosonde and 615 satellite-thickness profiles. Experimental results indicate that the quality of the analysis is almost independent of the number of batches (except when the ensemble is very small). This supports the use of a sequential algorithm. A parallel version of the algorithm is described and used to assimilate over 100 000 observations into a pair of 50-member ensembles. Its operation count is proportional to the number of observations, the number of analysis grid points, and the number of ensemble members. In view of the flexibility of the sequential filter and its encouraging performance on a NEC SX-4 computer, an application with a primitive equations model can now be envisioned.

Simple Selection Criteria for Drug-like Chemical Matter

Abstract: A simple pharmacophore point filter has been developed that discriminates between drug-like and nondrug-like chemical matter. It is based on the observation that nondrugs are often underfunctionalized. Therefore, a minimum count of well-defined pharmacophore points is required to pass the filter. The application of the filter results in 66−69% of subsets of the MDDR database to be classified as drug-like. Furthermore, 61−68% of subsets of the CMC database are classified as drug-like. In contrast, only 36% of the ACD are found to be drug-like. While these results are not quite as good as those obtained with recently described neural net approaches, the method used here has clear advantages. In contrast to a neural net approach and also in contrast to decision tree methods described recently, the pharmacophore filter has been developed by using “chemical wisdom” that is unbiased from fitting the structural content of specific drug databases to prediction models. Similar to decision tree methods, the pharmac...

An extended Kalman filter for quaternion-based orientation estimation using MARG sensors

Abstract: Presents an extended Kalman filter for real-time estimation of rigid body orientation using the newly developed MARG (magnetic, angular rate, and gravity) sensors. Each MARG sensor contains a three-axis magnetometer, a three-axis angular rate sensor, and a three-axis accelerometer. The filter represents rotations using quaternions rather than Euler angles, which eliminates the long-standing problem of singularities associated with attitude estimation. A process model for rigid body angular motions and angular rate measurements is defined. The process model converts angular rates into quaternion rates, which are integrated to obtain quaternions. The Gauss-Newton iteration algorithm is utilized to find the best quaternion that relates the measured accelerations and earth magnetic field in the body coordinate frame to calculated values in the earth coordinate frame. The best quaternion is used as part of the measurements for the Kalman filter. As a result of this approach, the measurement equations of the Kalman filter become linear, and the computational requirements are significantly reduced, making it possible to estimate orientation in real time. Extensive testing of the filter with synthetic data and actual sensor data proved it to be satisfactory. Test cases included the presence of large initial errors as well as high noise levels. In all cases the filter was able to converge and accurately track rotational motions.

Specification and design of a prototype filter for filter bank based multicarrier transmission

Abstract: The specifications of filter banks for multicarrier transmission systems with a large number of subchannels are discussed, with application to xDSL and power line communication in mind. The near perfect reconstruction (PR) modulated approach is considered and the importance, for the system, of the prototype filter delay is stressed. An existing design technique known to be particularly relevant to the context is revisited from a frequency sampling perspective. The performance results in terms of subchannel noise floor and delay are given for several filter lengths and an experimental validation is provided. Finally, an improvement to the design technique is proposed, which brings a gain of 3.3 dB in subchannel interference power level.

High-frequency modeling for cable and induction motor overvoltage studies in long cable drives

Abstract: High-frequency simulation models for power cables and motors are key tools to aid a better understanding of the overvoltage problem in pulsewidth modulation drives with long feeders. In this paper, frequency responses of the cable characteristic and the motor input impedances are obtained experimentally and suitable models are developed to match the experimental results. Several lumped segments incorporating a lossy representation of the line are used to model the cable. The cable and induction motor models may be implemented using a computational tool such as MATLAB, thereby providing a convenient method to analyze the overvoltage phenomena. Simulation and experimental results are presented for a typical 3-hp induction motor, showing the suitability of the developed simulation models. The most promising dv/dt filter networks are also investigated through simulation analysis, and a design approach based on a tradeoff between filter losses and motor peak voltage is proposed. Experimental results of an RC filter placed at the motor terminals demonstrate the validity of the simulation models.

The Mauna Kea Observatories Near-Infrared Filter Set. II. Specifications for a New JHKL'M' Filter Set for Infrared Astronomy

Abstract: We present a description of a new 1--5 $\mu$m filter set similar to the long-used JHKLM filter set derived from that of Johnson. The new Mauna Kea Observatories Near-Infrared (MKO-NIR) filter set is designed to reduce background noise, improve photometric transformations from observatory to observatory, provide greater accuracy in extrapolating to zero air mass, and reduce the color dependence in the extinction coefficient in photometric reductions. We have also taken into account the requirements of adaptive optics in setting the flatness specification of the filters. A complete technical description is presented to facilitate the production of similar filters in the future.

Vascular embolism prevention device employing filters

Abstract: A method and system for preventing embolism and optimizing flow to downstream organs in a blood flow circuit incident to performance of a treatment at a location in a blood vessel, by: introducing a first filter element into the blood vessel downstream of the location so that the first filter element obturates the blood vessel; performing the treatment; introducing a second filter element into the blood vessel upstream of the location so that the second filter element obturates the blood vessel; and, after the step of performing a treatment, bringing the first and second filter elements close to one another, radially collapsing the first and second filter elements and withdrawing the first and second filter elements from the blood vessel.

Air filtration arrangements having fluted media constructions and methods

Abstract: Filter arrangements include a barrier media in the form of fluted media treated with a deposit of fine fibers. The media is particularly advantageous in high temperature (greater than 140 to 240° F.) systems. Such systems may include engine systems, gas turbine systems, and fuel cell systems. Filter arrangements may take the form of media packs having a circular cross-section or a racetrack shaped cross-section, or media packs formed in a panel configuration.

Methods for aortic atherectomy

Abstract: A method for removing plaque from the aorta is disclosed. A filter is introduced into a region of interest within the patient's aorta. The filter is deployed downstream of a mobile aortic plaque within the aorta. An atherectomy assembly is operated to excise the plaque from the aorta. Emboli are captured by the filter. The filter and plaque are removed from the region of interest.

A particle filter for track-before-detect

Abstract: A Bayesian track-before-detect particle filter is proposed. The filter provides a sample based approximation to the distribution of the target state directly from pixel array data. The filter also provides a measure of the probability that a target is present.

Stochastic fair blue: a queue management algorithm for enforcing fairness

Abstract: This paper describes and evaluates stochastic fair blue (SFB), a novel technique for enforcing fairness among a large number of rows. SFB scalably detects and rate-limits non-responsive flows through the use of a marking probability derived from the blue queue management algorithm and a Bloom (1970) filter. Using analysis and simulation, SFB is shown to effectively handle non-responsive flows using an extremely small amount of state information.

Force field particle filter, combining ultrasound standing waves and laminar flow

Abstract: A continuous flow microparticle filter that combines megahertz frequency ultrasonic standing waves and laminar flow is described. The filter has a 0.25 mm, single half wavelength, acoustic pathlength at right angles to the flow. Standing wave radiation pressure on suspended particles drives them towards the centre of the acoustic pathlength. Clarified suspending phase from the region closest to the filter wall is drawn away through a downstream outlet. Experimental tests achieved >1000-fold clearance of 5 μm yeast cells, at a sample flow rate of 6 ml min −1 , from which the clarified aliquot is 1 ml min −1 . At this flow rate the average residence time in the sound field was 1 h was less than 1 K. The design criteria considered in the fabrication of this high performance device are discussed. A theoretical model of the filter’s efficiency, which considers the action of primary radiation force and the particle distribution across a laminar flow profile is presented here. The model predicts that totally clarified filtrate (i.e. zero suspended particles) may be drawn from the downstream outlet. The system described offers a generic approach to automated filtration in some applications. It is continuous flow thereby solving many of the problems of automation presented by batch filter methods and centrifuges. It could be developed for both larger scale and microfluidic applications.

Collapsible blood filter with optimal braid geometry

Abstract: The present invention is a collapsible blood filter for use during a vascular procedure, such as angioplasty or stent deployment. A filter made of braided filaments is located on the distal end of a delivery member, and the filter is deployed downstream of the vascular treatment site to capture emboli released during and immediately after the procedure. Optical braid geometry of the filter ensures that captured emboli will be retained during collapse and removal of the filter following the procedure.

Fast impulsive noise removal

Abstract: A generic n-dimensional filter with the primary purpose of eliminating impulsive-like noise is presented. This recursive nonlinear filter is composed of two conditional rules, which are applied independently, in any order, one after the other. It identifies noisy items by inspection of their surrounding neighborhood, and afterwards it replaces their values with the most "conservative" ones out of their neighbors' values. In this way, no new values are introduced and the histogram distribution range is conserved. This n-dimensional filter can be decomposed recursively to a lower dimensional space, each time generating two sets of n(n-1)-dimensional filters. This study, which focuses on the case of two-dimensional signals (gray scale images), explores one possible implementation of this new filter and orients the evaluation of its performance toward the median filter, as this filter is the basis of many more sophisticated filters for impulsive noise reduction. Tests were carried out using both real and artificial images. We found this new filter to be much faster than the median filter while performing comparably in terms of both image information conservation and noise reduction, which suggests that it could replace the median filter for the preliminary processing included in state-of-the-art noise removal filters. This new filter should either eliminate or attenuate most noisy pixels in synthetic and natural images not excessively contaminated. It has a slight smoothing effect on nonnoisy image regions. In addition, it is scalable, easily implemented, and adaptable to specific applications.

The Mauna Kea Observatories Near-Infrared Filter Set. I: Defining Optimal 1-5 $\mu$m Bandpasses

Abstract: A new MKO-NIR infrared filter set is described, including techniques and considerations given to designing a new set of bandpasses that are useful at both mid- and high-altitude sites. These filters offer improved photometric linearity and in many cases reduced background, as well as preserve good throughput within the JHKLM atmospheric windows. MKO-NIR filters have already been deployed with a number of instruments around the world as part of a filter consortium purchase to reduce the unit cost of filters. Through this effort we hope to establish, for the first time, a single standard set of infrared fitlers at as many observatories as possible.

Vascular filter system with guidewire and capture mechanism

Abstract: A removable vascular filter system for blocking micro- and macro-emboli while allowing the continued perfusion of blood comprises a filter membrane positioned on a guidewire, wherein a free end of the membrane sits tightly against the guidewire when the filter membrane is in a collapsed state and wherein the filter has a means for deploying the filter membrane to assume a position substantially normal to the longitudinal axis of the guidewire. The filter membrane is comprised of a fine mesh material which has a pore size capable of blocking emboli while allowing continued blood flow, a preferred embodiment of which comprises regularly spaced, laser-formed holes, and in which the membrane has a scalloped proximal profile. A capture mechanism is similarly described.

Adaptive filtering algorithms with selective partial updates

Abstract: In some applications of adaptive filtering such as active noise reduction, and network and acoustic echo cancellation, the adaptive filter may be required to have a large number of coefficients in order to model the unknown physical medium with sufficient accuracy. The computational complexity of adaptation algorithms is proportional to the number of filter coefficients. This implies that, for long adaptive filters, the adaptation task can become prohibitively expensive, ruling out cost-effective implementation on digital signal processors. The purpose of partial coefficient updates is to reduce the computational complexity of an adaptive filter by adapting a block of the filter coefficients rather than the entire filter at every iteration. In this paper, we develop a selective-partial-update normalized least-mean-square (NLMS) algorithm, and analyze its stability using the traditional independence assumptions and error-energy bounds. Selective partial updating is also extended to the affine projection (AP) algorithm by introducing multiple constraints. The new algorithms appear to have good convergence performance as attested to by computer simulations with real speech signals.

Apparatus and method for replacing aortic valve

Abstract: Apparatus and methods are disclosed for performing beating heart surgery. Apparatus is disclosed comprising a cannula having a proximal end and a distal end; an aortic filter in connection with the cannula, the aortic filter having a proximal side and a distal side; a check valve in connection with the cannula, the check valve disposed on the distal side of the aortic filter; and a coronary artery filter in connection with the cannula, the coronary artery filter having a proximal end and a distal end, and the distal end of the coronary artery filter extending distally away from the distal end of the cannula. A method is disclosed comprising providing apparatus for performing beating heart surgery; deploying the apparatus in an aorta; performing a procedure on the aortic valve; and removing the apparatus from the aorta.

Guided wave spatial filter

Abstract: The invention concerns a guided wave spatial filter (300) for receiving input radiation and outputting corresponding filtered output radiation, the filter comprising first and second waveguide sections (30, L3, L5) connected in series, the sections: (a) mutually matched for transmitting fundamental mode radiation components present in the input radiation therethrough to provide the output radiation; and (b) mutually mismatched for hindering higher-order mode radiation components present in the input radiation from propagating therethrough and contributing to the output radiation. The spatial filter (300) is implemented using rib waveguides (30) for the sections with associated relatively deeply and relatively shallowly etched structures (20, 310, 320) for imparting to the sections their radiation mode filtration characteristics. The spatial filter according to the invention can be incorporated into optical splitters and optical modulators to enhance their performance and desensitise them to higher-order mode radiation injected thereinto.

A new family of all-inductive dual-mode filters

Abstract: In this paper, we describe a new family of dual-mode filters that is based on the use of simple inductive discontinuities in a rectangular waveguide environment. The proposed filter structure can be analyzed and optimized very efficiently using multimode equivalent network representations, thus leading to a simple and rapid development procedure. In addition to theory, the measured performance of a number of filter structures is also presented, thereby fully validating the proposed filter concept.

Vascular filter system

Abstract: A removable vascular filter system for blocking micro- and macro-emboli while allowing the continued perfusion of blood comprises a filter membrane positioned on a guidewire, wherein a free end of the membrane sits tightly against the guidewire when the filter membrane is in a collapsed state and wherein the filter has a means for deploying the filter membrane to assume a position substantially normal to the longitudinal axis of the guidewire. The filter membrane is comprised of a fine mesh material which has a pore size capable of blocking emboli while allowing continued blood flow, a preferred embodiment of which comprises regularly spaced, laser-formed holes, and in which the membrane has a scalloped proximal profile.

The Use of Butterworth Filters for Trend and Cycle Estimation in Economic Time Series

Abstract: Long-term trends and business cycles are usually estimated by applying the Hodrick and Prescott (HP) filter to X-11 seasonally adjusted data. A two-stage procedure is proposed in this article to improve this methodology. The improvement is based on (a) using Butterworth or band-pass filters specifically designed for the problem at hand as an alternative to the HP filter, (b) applying the selected filter to estimated trend cycles instead of to seasonally adjusted series, and (c) using autoregressive integrated moving average models to extend the input series with forecasts and backcasts. It is shown in the article that the HP filter is a Butterworth filter and that, if a model-based method is used for seasonal adjustment, it is possible to give a fully model-based interpretation of the proposed procedure. In this case, one can compute forecasts and mean squared errors of the estimated trends and cycles. The procedure is illustrated with several examples.

Controlled effective coupling coefficients for film bulk acoustic resonators

Abstract: In an array of acoustic resonators, the effective coupling coefficient of first and second filters are individually tailored in order to achieve desired frequency responses. In a duplexer embodiment, the effective coupling coefficient of a transmit band-pass filter is lower than the effective coupling coefficient of a receive band-pass filter of the same duplexer. In one embodiment, the tailoring of the coefficients is achieved by varying the ratio of the thickness of a piezoelectric layer to the total thickness of electrode layers. For example, the total thickness of the electrode layers of the transmit filter may be in the range of 1.2 to 2.8 times the total thickness of the electrode layers of the receive filter. In another embodiment, the coefficient tailoring is achieved by forming a capacitor in parallel with an acoustic resonator within the filter for which the effective coupling coefficient is to be degraded. Preferably, the capacitor is formed of the same materials used to fabricate a film bulk acoustic resonator (FBAR). The capacitor may be mass loaded to change its frequency by depositing a metal layer on the capacitor. Alternatively, the mass loading may be provided by forming the capacitor directly on a substrate.

RF MEMS‐based tunable filters

Abstract: This paper overviews the application of RF MEMS switches in tunable filters as well as circuit developments for bandpass filters covering 110 MHz to 2.8 GHz. RF MEMS have several desirable features, including small size, low power requirements, and low loss. The basic operation of Raytheon's RF MEMS capacitive membrane switch is described. An overview of the technique used to integrate the switch into a variable capacitor structure with sixteen capacitance states is provided. Variable capacitor structures are used to construct multipole lumped bandpass filter designs, each with sixteen states. Finally, measured data from two representative five- and six-pole bandpass filters are presented. Characterization data demonstrates that the insertion loss for the five-pole filter using on-chip inductors was between 6.6 and 7.3 dB, and between 3.7 and 4.2 dB for the six-pole filter using off-chip inductors. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE11: 276-284, 2001.

High-input impedance voltage-mode universal biquadratic filter using three plus-type CCIIs

Abstract: A new three-input single-output voltage-mode universal biquadratic filter with high-input impedance using only three plus-type second-generation current conveyors (CCIIs) is presented. The proposed configuration uses only two capacitors and two resistors and can realize all the standard filter functions, that is, high-pass, bandpass, low-pass, notch, and allpass filters without changing the passive elements. The proposed circuit has no requirements for component matching conditions. The use of only plus-type CCIIs simplifies the configuration.

Soil Suction Measurements by Filter Paper

Abstract: This paper reports on an evaluation of wetting and drying filter paper suction calibration and soil total and matric suction measurement techniques of filter paper method. Calibration of the method was investigated by constructing two calibration curves; one by using the process of wetting the filter papers through vapor flow and the other by using the method of drying the filter papers through fluid flow. The wetting curve was constructed using sodium chloride (NaCl) salt solutions and Schleicher & Schuell No. 589-WH filter papers. It was found that the change in the wetting suction curve is very sensitive to minor changes in filter paper water content below about 1.5 log kPa (2.5 pF) suction. The drying curve was established by employing both pressure plate and pressure membrane devices and the same filter papers. In developing the filter paper calibration curves, the capabilities, pitfalls, and limitations of the method are also discussed.

Piezoelectric resonator structures with a bending element performing a voltage controlled switching function

Abstract: The invention relates to resonator structures of radio communication apparatus. According to the invention, a micromechanical switch and a resonator are realized in a single combined structure. Combination of switch and resonator structures allows the manufacture of very compact filter and resonator structures needed for multi-system mobile communication means.