Showing papers on "Filter (video) published in 2002"

Multirate Systems and Filter Banks

Abstract: The outline of this chapter is as follows. Section 2 reviews various types of existing finite impulse response (FIR) and infinite impulse response (IIR) two-channel filter banks. The basic operations of these filter banks are considered and the requirements are stated for alias-free, perfect-reconstruction (PR), and nearly perfect-reconstruction (NPR) filter banks. Also some efficient synthesis techniques are referred to. Furthermore, examples are included to compare various two-channel filter banks with each other. Section 3 concentrates on the design of multi-channel (M-channel) uniform filter banks. The main emphasis is laid on designing these banks using tree-structured filter banks with the aid of two-channel filter banks and on generating the overall bank with the aid of a single prototype filter and a proper cosine-modulation or MDFT technique. In Section 4, it is shown how octave filter banks can be generated using a single two-channel filter bank as the basic building block. Also, the relations between the frequency-selective octave filter banks and discrete-time wavelet banks are briefly discussed. Finally, concluding remarks are given in Section 5.

A new impulse detector for switching median filters

Abstract: A new impulse noise detection technique for switching median filters is presented, which is based on the minimum absolute value of four convolutions obtained using one-dimensional Laplacian operators. Extensive simulations show that the proposed filter provides better performance than many of the existing switching median filters with comparable computational complexity. In particular, the proposed filter is directed toward improved line preservation.

A sequential particle filter method for static models

Abstract: SUMMARY Particle filter methods are complex inference procedures, which combine importance sampling and Monte Carlo schemes in order to explore consistently a sequence of multiple distributions of interest. We show that such methods can also offer an efficient estimation

Grid current regulation of a three-phase voltage source inverter with an LCL input filter

Abstract: Many grid connected power electronic systems, such as STATCOMs, UPFCs and distributed generation system interfaces, use a voltage source inverter (VSI) connected to the supply network through a filter. This filter, typically a series inductance, acts to reduce the switching harmonics entering the distribution network. An alternative filter is a LCL network, which can achieve reduced levels of harmonic distortion at lower switching frequencies and with less inductance, and therefore has potential benefits for higher power applications. However, systems incorporating LCL filters require more complex control strategies and are not commonly presented in literature. This paper proposes a robust strategy for regulating the grid current entering a distribution network from a three-phase VSI system connected via an LCL filter. The strategy integrates an outer loop grid current regulator with inner capacitor current regulation to stabilise the system. A synchronous frame PI current regulation strategy is used for the outer grid current control loop. Linear analysis, simulation and experimental results are used to verify the stability of the control algorithm across a range of operating conditions. Finally, expressions for "harmonic impedance" of the system are derived to study the effects of supply voltage distortion on the harmonic performance of the system.

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 mm filter set similar to the long-used JHKLM filter set derived from that of Johnson. The new Mauna Kea Observatories Near-Infrared 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.

Method for detecting transverse mode vibrations in an ultrasonic hand piece/blade

Abstract: A method for detecting transverse mode vibrations in an ultrasonic hand piece/blade for determining the existence of unwanted vibration in the hand piece/blade. A tracking filter centered at the drive frequency of the generator, is used to monitor the drive frequency of the ultrasonic generator and attenuate the drive signal when it exceeds a predetermined level. The tracking filter has a wide pass band. Alternatively, a tracking filter having a pass band which is divided into several regions is used to avoid other longitudinal resonances, such as a resonance at a second harmonic, or other spectral features that would otherwise detract from the tracking accuracy of the filter.

Speed estimation of an induction motor drive using an optimized extended Kalman filter

Abstract: This paper presents a novel method to achieve good performance of an extended Kalman filter (EKF) for speed estimation of an induction motor drive. A real-coded genetic algorithm (GA) is used to optimize the noise covariance and weight matrices of the EKF, thereby ensuring filter stability and accuracy in speed estimation. Simulation studies on a constant V/Hz controller and a field-oriented controller (FOC) under various operating conditions demonstrate the efficacy of the proposed method. The experimental system consists of a prototype digital-signal-processor-based FOC induction motor drive with hardware facilities for acquiring the speed, voltage, and current signals to a PC. Experiments comprising offline GA training and verification phases are presented to validate the performance of the optimized EKF.

Methods, systems, and devices for providing embolic protection and removing embolic material

Abstract: A filter device is adapted to function as a guidewire, an exchange guidewire, and provide embolic protection during a procedure. The filter device (10) includes a filter assembly (42) that is either integral with or coupled to a guide member (12). The filter assembly (42) includes a plurality of struts (52) that expand outwardly to deploy a filter (50) that collects or captures material flowing along the blood vessel within which the filter device (10) is deployed. The plurality of struts (52) is constrained by a restraining member or mechanism (24) that prevents the plurality of struts from expanding or extending outwardly to deploy the filter. Cooperating with the restraining member or mechanism is an actuating assembly (20) that is adapted to release the restraining member (24) or mechanism and enable the filter to be deployed from the guide member (12). A capture catheter (90) that cooperates with the filter device (10) and substantially surrounds the filter (50) during the removal of the filter device (10).

Intravascular filter system

Abstract: A removable intravascular filter system traps emboli and other solid materials in connection with intravascular medical procedures such as the placement of a stent or a catheter balloon. The system involves a hollow guidewire and an actuating wire movable within the guidewire to actuate the filter membrane. Embodiments of the filter system include biased closed and biased open filter configurations, and are easily routed through a patient's artery and deployed. Optionally, the actuating wire can be removed and a substitute wire can be inserted into the hollow guidewire. Control mechanisms can help the operator limit movement of the actuating wire during deployment and/or collapse of the filter membrane. Preferred filter membranes are configured to maximize both blood flow and emboli capture.

A design of the novel coupled-line bandpass filter using defected ground structure with wide stopband performance

Abstract: In this paper, a novel three-pole coupled-line bandpass filter with a microstrip configuration is presented. Presented bandpass filters use defected ground structure (DGS) sections to simultaneously realize a resonator and an inverter. The proposed coupled-line bandpass filter provides compact size with low insertion-loss characteristic. Furthermore, a DGS shape for a microstrip line is newly proposed. The proposed DGS unit structure has a resonance characteristic in some frequency band. The proposed coupled-line filter can provide attenuation poles for wide stopband characteristic due to resonance characteristic of DGS. The equivalent circuit for the proposed DGS unit section is described. The equivalent-circuit parameters for DGS are extracted by using a three-dimensional finite-element-method calculation and simple circuit analysis method. A design method for the proposed coupled-line filter is derived based on coupled-line filter theory and the equivalent circuit of the DGS. The experimental results show excellent agreements with theoretical simulation results.

Land data assimilation and estimation of soil moisture using measurements from the Southern Great Plains 1997 Field Experiment

Abstract: [1] Remotely sensed microwave measurements provide useful but indirect observations of surface soil moisture. Ground-based measurements are more direct but are very localized and limited in coverage. Model predictions provide a more regional perspective but rely on many simplifications and approximations and depend on inputs that are difficult to obtain over extensive areas. The only effective way to achieve soil moisture estimates with the accuracy and coverage required for hydrologic and meteorological applications is to merge information from satellites, ground-based stations, and models. In this paper we describe a convenient data merging (or data assimilation) procedure based on an ensemble Kalman filter. This procedure is illustrated with an application to the Southern Great Plains 1997 (SGP97) field experiment. It uses land surface and radiative transfer models to derive soil moisture estimates from airborne L band microwave observations and ground-based measurements of micrometeorological variables, soil texture, and vegetation type. The ensemble filter approach is appealing because (1) it can accommodate a wide range of models, (2) it can account for input and measurement uncertainties, (3) it provides information on the accuracy of its estimates, and (4) it is relatively efficient, making large-scale applications feasible. Results from our SGP97 application of the ensemble Kalman filter include large-scale maps (∼10,000 km2) of soil moisture estimates and estimation error standard deviations for the entire month long experiment and comparisons of filter soil moisture and latent heat estimates to ground truth measurements (gravimetric and flux tower observations). The ground truth comparisons show that the filter is able to track soil moisture fluctuations. The filter estimates are significantly better than those from an “open loop” simulation that includes the same ground-based data but does not incorporate radio brightness measurements. Overall, the results from this field test indicate that the ensemble Kalman filter is an accurate, efficient, and flexible data assimilation procedure that is able to extract useful information from remote sensing measurements.

Adaptive Kalman Filtering for Low Cost INS/GPS

Abstract: GPS and low cost INS sensors are widely used for positioning and attitude determination applications. Low cost inertial sen- sors exhibit large errors which are compensated using position and velocity updates from GPS. Combining both sensors using a Kalman filter provides high accuracy real time navigation. The Kalman filter relies on the definition of the correct mea- surement and process noise matrices which are generally de- fined a priori and remain fixed throughout the processing run. Adaptive Kalman filtering techniques use the residual sequences to adapt the stochastic properties of the filter on- line to correspond to the temporal dependence of the errors involved. This paper examines the use of three adaptive fil- tering techniques. These are artificially scaling the predicted Kalman filter covariance, the Adaptive Kalman Filter and Mul- tiple Model Adaptive Estimation. The algorithms are tested with the IESSG's GPS and inertial data simulation software. A trajectory taken from a real marine trial is used to test the dynamic alignment of the inertial sensor errors. Results show that on-line estimation of the stochastic properties of the inertial system can significantly improve the speed of the dynamic alignment and potentially improve the overall navigation accuracy and integrity.

Transmit Wiener filter for the downlink of TDDDS-CDMA systems

Abstract: We derive the transmit Wiener filter for DS-CDMA systems which depends upon the noise power at the receivers. We show that the transmit Wiener filter converges to the transmit matched filter and the transmit zero-forcing filter for low and high signal-to-noise-ratio, respectively. Simulation results show the superiority of the transmit Wiener filter compared to the other two transmit filters. Moreover, we observe that the application of the three transmit filters and the respective receive filters lead to similar results.

Method and apparatus for controlling data provided to a mobile device

Abstract: Techniques are provided for communicating data to a mobile device. A system receives a request for data from a mobile device. The system identifies filter criteria associated with the mobile device. The filter criteria is applied to a set of data to identify particular data elements that satisfy the filter criteria. The identified data elements are then transmitted to the mobile device.

A laser-based people tracker

Abstract: Describes a method for real-time tracking of people in everyday environments, using multiple planar laser range-finders. People tracking is a well-studied problem in machine vision; we adapt some of those methods to laser range-finders. We group range measurements into entities such as blobs and objects, and use a Kalman filter to estimate trajectories for these objects. The filter is able to generate smooth trajectories, even when objects are occluded. The paper presents our evaluation of the tracker's performance in a series of four experiments.

Stationary frame harmonic reference generation for active filter systems

Abstract: Harmonic reference generators for active filter systems are commonly implemented in the synchronous reference frame, so that simple low- or high-pass filter functions can be used depending on the requirements of a particular application. High-pass filters in particular are used when the reference generator is required to produce an "everything but the fundamental" target waveform. This paper presents a stationary frame notch filter equivalent to a high-pass synchronous frame harmonic reference generator for such systems. The use of the stationary frame allows for quicker calculation of the reference generation in a discrete digital implementation, and also allows classical control techniques to be used to analyze the active filter system without requiring synchronous frame transformations of the outside system model. Both simulation (continuous and discrete) and experimental results showing the equivalency of the stationary and synchronous frame reference generation process are presented using both shift and delta-operator-based infinite-impulse response digital filters.

Design and implementation of an inverter output LC filter used for dv/dt reduction

Abstract: This paper presents the design and analysis of a LC output filter for use with IGBT-based motor drive inverters. The LC filter is used to limit the rate of rise of the inverter output voltage and reduce common mode noise to the motor. In typical applications where dv/dt is limited to 100-500 V//spl mu/s, the resonant frequency of the filter is above the switching frequency. A diode bridge must therefore be used to clamp the resonant voltage. Resistors are also used to help dissipate the energy stored in the resonant circuit. Crucial to the design of the filter is the handling of the additional losses in the filter. The paper describes the design considerations for such a filter for use in a 460 V induction motor drive. The losses in the circuit are estimated to show the limitations of the filter. Experimental results illustrate the control of dv/dt at the inverter terminals, and the reduced peak voltage at the motor end of a long cable.

Program guide data selection device

Abstract: A television has a programming guide data selection device for selecting data corresponding to programming content. A processor (2) filters programming guide data according to different filter categories such as time, channel and content type, and also individual filter ranges, and provides a display on the television by means of a graphical user interface process (27). The interface provides horizontal and vertical scroll bars (V,H) which each comprise a plurality of scroll bar elements signifying individual filter ranges of the filter categories, so that when selected individually, the scroll bar elements of the vertical scroll bar signify individual program content items from the program data that fall within the filter category and range of the selected horizontal scroll bar element, at least one of the scroll bar elements of the horizontal scroll bar comprising a multiple depiction of more than one of said individual filter ranges of filter categories, whereby an individual one of the filter ranges may be selected from the multiple depiction.

Security enabled network access control

Abstract: An access control system including a network device having a plurality of network interfaces for receiving and transmitting packets of data, the network device including a forwarding element to apply filter rules to the packets, and a filter rule constructor engine associated with said forwarding element to receive access control rules and decryption information for a security protocol, derive from the access control rules and security information a set of filter rules to be applied to packet headers encrypted with the security protocol, and transmit the set of filter rules to the at least one forwarding element.

Learning Sparse Topographic Representations with Products of Student-t Distributions

Abstract: We propose a model for natural images in which the probability of an image is proportional to the product of the probabilities of some filter outputs. We encourage the system to find sparse features by using a Student-t distribution to model each filter output. If the t-distribution is used to model the combined outputs of sets of neurally adjacent filters, the system learns a topographic map in which the orientation, spatial frequency and location of the filters change smoothly across the map. Even though maximum likelihood learning is intractable in our model, the product form allows a relatively efficient learning procedure that works well even for highly overcomplete sets of filters. Once the model has been learned it can be used as a prior to derive the "iterated Wiener filter" for the purpose of denoising images.

Stationary filter for linear minimum mean square error estimator of discrete-time Markovian jump systems

Abstract: We derive in this paper a stationary filter for the linear minimum mean square error estimator (LMMSE) of discrete-time Markovian jump linear systems (MJLSs). We obtain the convergence of the error covariance matrix of the LMMSE to a stationary value under the assumption of mean square stability of the MJLS and ergodicity of the associated Markov chain. It is shown that there exists a unique solution for the stationary Riccati filter equation and, moreover, this solution is the limit of the error covariance matrix of the LMMSE. The advantage of this scheme is that it is very easy to implement and all calculations can be performed off-line, leading to a linear time-invariant filter.

Markov chain Monte Carlo, Sufficient Statistics, and Particle Filters

Abstract: This article considers how to implement Markov chain Monte Carlo (MCMC) moves within a particle filter. Previous, similar, attempts have required the complete history (“trajectory”) of each particle to be stored. Here, it is shown how certain MCMC moves can be introduced within a particle filter when only summaries of each particles' trajectory are stored. These summaries are based on sufficient statistics. Using this idea, the storage requirement of the particle filter can be substantially reduced, and MCMC moves can be implemented more efficiently. We illustrate how this idea can be used for both the bearingsonly tracking problem and a model of stochastic volatility. We give a detailed comparison of the performance of different particle filters for the bearings-only tracking problem. MCMC, combined with a sensible initialization of the filter and stratified resampling, produces substantial gains in the efficiency of the particle filter.

A Control Method to Damp Oscillation in the Input LC Filter of AC-DC PWM Converters

Abstract: A control method to damp oscillation in the input LC filter of AC-DC PWM converters is proposed in this paper. The oscillation in the input LC filter of AC-DC PWM converters is damped by using a virtual resistor that can be connected either in series to or parallel with filter inductor or capacitor. Because no real resistor is used, the efficiency of the converters is not sacrificed. The required additional sensor and implementation of the virtual resistor in the control algorithm is strongly influenced on how the virtual resistor is connected to the LC filter. We need an additional current sensor if the virtual resistor is connected in series to the filter inductor or capacitor and an additional voltage sensor if connected in parallel. Simulated and experimental results are included to verify the proposed method.

Method and system for a role-based access control model with active roles

Abstract: A method, system, apparatus, and computer program product are presented for managing access to resources with a role-based access control model that includes dynamic update functionality using role filters and capability filters. Rather than directly connecting individual users to a role, a role filter is defined for a role. The role filter is evaluated to determine which users should be matched to a given role, and matching users are then automatically associated with the given role. In addition to its role filter, each named role contains a set of capabilities. Each capability contains a set of access conditions and a capability filter. Each access condition has a set of rights. Rather than directly connecting individual resources to a capability, the administrator can define a capability filter for each capability. As target instances are added, deleted, or changed, capability filters are re-evaluated to maintain the appropriate set of relationships.

Method and system for filter based message processing in a unified messaging system

Abstract: A method and system for processing messages in a unified messaging system. In particular, the system enables legacy e-mail, voice mail and facsimile systems to be integrated with a unified messaging system. The system includes a filter or mechanism which enables the user to filter certain message attributes such as the identification of the sender, recipient or the subject header or the message type to enable messages to be processed in accordance with the recipients wishes.

Temporary intraluminal filter guidewire and methods of use

Abstract: The present invention is a temporary intraluminal filter guidewire for use during interventional procedures, such as angioplasty or stent deployment. A braided filter is mounted near the distal end of a steerable guidewire, which guides a therapeutic catheter. An actuator rod slides over the guidewire and is removably connected to the filter. The rod controls relative displacement of the filter ends, causing transformation of the filter between a deployed configuration and a collapsed configuration. Wire having enhanced radiopacity is included in the filter to provide visualization under fluoroscopy.

Endovascular guidewire filter and methods of use

Abstract: A filter device for temporary placement of a filter in an artery or vein is disclosed. The devices include (1) an elongate tubular member having a single or double side-wire loop, (2) an elongate member having a filter bonded to a circular rim joined by a plurality of tethers and an independently moveable tether, and (3) an elongate member having a parachute filter joined by a plurality of flexible struts. The filter conforms to the interior of a vessel wall when expanded and contracts to a consistent diameter without bunching when stowed. The filter devices may act as guidewires for guiding a therapeutic catheter to a region of interest within a vessel. Methods of using the filter device to entrap and remove embolic material from a vessel during endovascular procedures are also disclosed.