Showing papers on "Filter (video) published in 1994"

Linear minimum mean square error estimation for discrete-time Markovian jump linear systems

Abstract: The linear minimum mean square error estimator (LMMSE) for discrete-time linear systems subject to abrupt changes in the parameters modeled by a Markov chain /spl theta/(k)/spl epsiv/{1...,N} is considered. The filter equations are derived from geometric arguments in a recursive form, resulting in an on-line algorithm suitable for computer implementation. The author's approach is based on estimating x(k)1/sub {/spl theta/(k/=i}) instead of estimating directly x(k). The uncertainty introduced by the Markovian jumps increases the dimension of the filter to N(n+1), where n is the dimension of the state variable. An example where the dimension of the filter can be reduced to n is presented, as well as a numerical comparison with the IMM filter. >

Vena cava filter

Abstract: A vascular filter comprises an emboli-capturing portion having a set of helical filter-wires joined at a central region and extending in a given direction along the blood vessel in a diverging relationship to the axis of the filter, the wires terminating in free ends constructed to engage the walls of said vessel. A major mid-portion of the length of the free ended wires are of generally helical form, cooperatively related to form an effective emboli capturing array. Anchoring is accomplished by a separate assembly formed of struts and anchoring devices. A parallelogram supporting strut assembly and other means for providing linear engagement with the wall of the vena cava are shown. The parallelogram structure is shown to have filter capability by itself as well.

Video scaling method and device

Abstract: A linear interpolator and decimating FIR filter with constant coefficients may be used in various configurations to scale a still or moving color video image horizontally (changing the number of pixels per row) or vertically (changing the number of pixels per column). For downscaling, the input pixel stream is initially upscaled with an interpolator by an upscaling factor of between one and two chosen so that the result can be subsequently downscaled with a decimation-by-power-of-two finite impulse response (FIR) filter to provide the desired final scaling. Upscaling is a special case accomplished by means of linear interpolation. Vertical and horizontal scaling may be performed with different, independent scaling factors.

Multirate Digital Signal Processing: Multirate Systems, Filter Banks, Wavelets

Abstract: From the Publisher: Illustrates the properties of various filter banks, enabling readers to distinguish between their diverse types. Provides design methodologies for multirate filters and filter banks. Since much of the material is quite advanced, the text features many figures and examples to aid understanding. Includes an international bibliography containing approximately 150 references to encourage readers to learn more about this fascinating and complex subject.

Fingerprint controlled public key cryptographic system

Abstract: A public key cryptographic system is implemented as follows. In an enrolment apparatus, the unique number for use in generating the public key and private key of the system is generated by manipulation of fingerprint information of a subscriber. A filter is then generated which is a function both of the Fourier transform of the subscriber's fingerprint(s) and of the unique number. This filter is stored on a subscriber card. When the subscriber wishes to generate his public or private key, he inputs his card to a card reader of an apparatus and places his finger(s) on a fingerprint input. The apparatus generates an optical Fourier transform from the fingerprint input. The Fourier transform signal is incident on to a spatial light modulator programmed with the filter information from the card. An inverse transform is generated from the filtered signal and this is used to regenerate the unique number. The apparatus also has a subsystem for utilizing the private key to decrypt an input encrypted message.

Federated Kalman filter simulation results

Abstract: This paper describes federated filter applications to integrated, fault-tolerant navigation systems, with emphasis on real-time implementation issues and numerical simulation results. The federated filter is a near-optimal estimator for decentralized, multi-sensor data fusion. Its decentralized estimation archi- tecture is based on theoretically sound information-sharing principles. A federated filter consists of one or more sensor- dedicated local filters, generally operating in parallel, plus a master combining filter. The master filter periodically com- bines (fuses) the local filter solutions to form the best total solution. Fusion generally occurs at a reduced rate, relative to the local measurement rates. The method can provide sig- nificant improvements in data throughput, fault tolerance, and system modularity. Numerical simulation results are pre- sented for an example multi-sensor navigation system. These results demonstrate federated filter performance characteristics in terms of estimation accuracy, fault-tolerance, and computation speed. This work was supported by the Defense Small Business Innovation

Method and apparatus for analyzing a neural network within desired operating parameter constraints

Abstract: A distributed control system (14) receives on the input thereof the control inputs and then outputs control signals to a plant (10) for the operation thereof. The measured variables of the plant and the control inputs are input to a predictive model (34) that operates in conjunction with an inverse model (36) to generate predicted control inputs. The predicted control inputs are processed through a filter (46) to apply hard constraints, the values of which are received from a control parameter block (22). During operation, predetermined criterion stored in the control parameter block (22) are utilized by a cost minimization block (42) to generate an error control signal which is minimized by the inverse model (36) to generate the control signals. The system works in two modes, an analyze mode and a runtime mode. In the analyze mode, the predictive model (34) and the inverse model (36) are connected to either training data or simulated data from the analyzer (30) and the operation of the plant (10) evaluated. The values of the hard constraints in filter (46) and the criterion utilized for the cost minimization (42) can then be varied to change the constraints on the control signals input to the control network, the predicted output of the predictive model (34) and the hard constraints stored in the filter (46). Cost coefficients can be utilized as the criterion to set the input values in accordance with predetermined cost constraints.

Efficient packet demultiplexing for multiple endpoints and large messages

Abstract: This paper describes a new packet filter mechanism that efficiently dispatches incoming network packets to one of multiple endpoints, for example address spaces. Earlier packet filter systems iteratively applied each installed filter against every incoming packet, resulting in high processing overhead whenever multiple filters existed. Our new packet filter provides an associative match function that enables similar but not identical filters to be combined together into a single filter. The filter mechanism, which we call the Mach Packet Filter (MPF), has been implemented for the Mach 3.0 operating system and is being used to support endpoint-based protocol processing, whereby each address space implements its own suite of network protocols. With large numbers of registered endpoints, MPF outperforms the earlier BSD Packet Filter (BPF) by over a factor of four. MPF also allows a filter program to dispatch fragmented packets, which was quite difficult with previous filter mechanisms.

Direct sequence code division multiple access (DS-CDMA) communication system and a receiver for use in such a system

Abstract: A DS-CDMA system comprises at least one transmitter and at least one receiver operating on a dedicated signal channel which is used by other DS-CDMA operators in a non-synchronous way. A receiver for use in such a DS-CDMA system includes a data aided multiuser interference canceller (38) comprising a feedforward filter (48) connected to a subtracting stage (50). A decision stage (52) is connected to an output of the subtracting stage (50). Decisions from the decision stage (52) are stored in a memory which also stores preliminary decisions made on the signal applied to the feedforward filter (48) by a simple receiver (46). These decisions are applied to a feedback filter (58) the output of which is connected to the subtracting stage (50) thereby removing the effects of pre-cursive and post-cursive interference. The input to, and output from, the decision stage 52 are compared and the difference is used for adjusting the tap weights of the feedforward and feedback filters (48,58). In the case of a single input, single output, the feedforward filter (48) comprises a fractionally spaced equalizer which despreads and filters the DS-CDMA signal. In the case of multiple input, multiple output, the received signal is despread in a bank of code matched filters and the output is applied to the canceller (38) in which the feedforward filter (48) comprises a linear synchronous equalizer.

Orthogonal time-varying filter banks and wavelet packets

Abstract: Considers the construction of orthogonal time-varying filter banks. By examining the time domain description of the two-channel orthogonal filter bank the authors find it possible to construct a set of orthogonal boundary filters, which allows to apply the filter bank to one-sided or finite-length signals, without redundancy or distortion. The method is constructive and complete. There is a whole space of orthogonal boundary solutions, and there is considerable freedom for optimization. This may be used to generate subband tree structures where the tree varies over time, and to change between different filter sets. The authors also show that the iteration of discrete-time time-varying filter banks gives continuous-time bases, just as in the stationary case. This gives rise to wavelet, or wavelet packet, bases for half-line and interval regions. >

Optimum loop filter in hybrid coders

Abstract: Examines the role of the loop/interpolation filter in the motion compensation loop of hybrid coders. Using the Wiener filtering concept and the statistical model developed by Chen and Pang (1992), the optimum filter that minimises the prediction error has been found. The result is expressed in an explicit form in terms of a correlation parameter, /spl rho/ and an inaccuracy parameter, /spl alpha/. It explains many current practices in MPEG and H.261 coders, as well as the leakage predictor, 3-tap versus 8-tap filters and other related issues. The analysis shows that minimum bit rate can only be achieved if the loop filter matches the statistical characteristic of the motion-compensated signal. Furthermore, since the motion noise characteristic could be very different in the horizontal and vertical direction for many sequences, the decision to deploy the optimum filter should be made separately in the two directions. The paper also derives the scalar loop filter in DCT domain. The scalar filter is sub-optimal, but it requires less computational load than the spatial domain filter (64 versus 484 multiplications per 8/spl times/8 block). Experiments show that it performs almost as efficiently as the optimum 3-tap spatial domain filter, thus ascertaining that its performance has not been significantly compromised by the scalar requirement. Experimental simulations on test sequences confirm the theoretical optimum results, and indirectly show that the simple statistical model used in the derivation is adequate. >

A 3D State Space Formulation of a Navigation Kalman Filter for Autonomous Vehicles

Abstract: : The Kalman Filter has many applications in mobile robotics ranging from perception, to position estimation, to control. This report formulates a navigation Kalman Filter. That is, one which estimates the position of autonomous vehicles. The filter is developed according-to the state space formulation of Kalman's original papers. The state space formulation is particularly appropriate for the problem of vehicle position estimation. This filter formulation is fairly general. This generality is possible because the problem has been addressed

Filter module with degassing feature

Abstract: There is disclosed a pressurizable filter module for aqueous media having a degassing feature, the improvement comprising the use of a hydrophobic membrane between the inlet plenum of the filter module and the pressure relief valve.

A low-power, area-efficient digital filter for decimation and interpolation

Abstract: The area and power consumption of oversampled data converters are governed largely by the associated digital decimation and interpolation filters. This paper presents a low-power, area-efficient, mask-programmable digital filter for decimation and interpolation in digital-audio applications. Several architectural and implementation features reduce the complexity of the filter and allow its realization in a die area of only 3670 mils/sup 2/ (2.37 mm/sup 2/) in a 1-/spl mu/m CMOS technology. The use of simple multiplier-free arithmetic logic and a new memory addressing scheme for multi rate digital filters results in a power consumption of only 18.8 mW from a 5-V supply and 6.5 mW from a 3-V supply. The memory addressing scheme and the programmable functionality of the filter are general enough to implement a wide class of FIR and IIR single-rate and multi-rate digital filters. >

Direct sequence spread spectrum matched filter acquisition in frequency-selective Rayleigh fading channels

Abstract: This paper presents the performance of a matched filter acquisition scheme in nonselective and frequency-selective Rayleigh fading channels. This acquisition scheme employs a reference filter to estimate the variance of the interference at the output of the detecting matched filter. Expressions for probability of detection and probability of false alarm are derived and the mean acquisition time is evaluated for various channel and system parameters. The results presented show the relationship between channel and system parameters and the system performance. >

Design of filters to detect a noisy target in nonoverlapping background noise

Abstract: Two types of filter are proposed to detect a noisy target embedded in nonoverlapping background noise by optimization of two proposed criteria that are used in the assessment of filter design and performance. Criterion 1 is defined as the ratio of the square of the expected value of the correlation-peak amplitude to the expected value of the output-signal energy. Criterion 2 is defined as the ratio of the square of the expected value of the correlation-peak amplitude to the average output-signal variance. It is shown that, for the nonoverlapping target and scene noise models, the target window and the scene noise window affect the filter functions significantly. Computer-simulation tests of the generalized optimum filter for various kinds of noisy input image are provided to investigate filter performance in terms of peak-to-output-energy ratio, discrimination against undesired objects, and tolerance to target distortion (for example, target rotation and scaling). We compare the results with those of other filters to verify the performance of the optimum filters.

Digital receiver for variable data rate communications

Abstract: A digital receiver includes a tuner and a demodulator that obtains a modulated signal carried in a received analog signal. A digital-to-analog converter operates at a preselected fixed sampling rate on the modulated signal to produce a first sequence of digitized samples. The first sequence of digitized samples is processed by a digital rotator to frequency-and phase-correct the first sequence of digitized samples. A controllable digital filter processes the first sequence to produce a filter output including a second sequence of digitized samples at a symbol rate. The second sequence is processed to ascertain a symbol rate of the modulated signal. The controllable filter coefficients are automatically varied to accommodate changes in the symbol rate of the modulated signal, so that the sampling rate of the digital-to-analog converter need not change. The second sequence is processed by post detection automatic gain control to produce a receiver output including a sequence of scaled and leveled digitized samples at the symbol rate.

Simple CAD procedure for microwave filters and multiplexers

Abstract: The design of microwave filters and multiplexers requires a common step before actual hardware implementation, namely, the identification of a number of specific ideal electrical components with actual waveguide discontinuities. In the past, this step was accomplished semi-analytically using approximate single-mode discontinuity models. The complete filter or multiplexer could then be assembled, but additional final tuning or optimization with a large number of parameters was generally required. In this paper, we propose an alternative technique for the design of microwave filters or multiplexers that directly uses a full-wave electromagnetic simulator and that effectively decomposes the complex design task into a series of simple sub-tasks with clearly identified objectives. The procedure described only involves a limited number of actual physical parameters at each step so that it is computationally very efficient and rapidly convergent. >

Method and apparatus for enhancing sharpness of a sequence of images subject to continuous zoom

Abstract: A bandpass enhancement filter (10) has a pass-band that tracks changes in spatial frequency due to the use of a zooming process upon a digital image signal The primary pass-band of the enhancement filter is derived from a combination of a plurality of secondary bandpass filter sections (30a-30d), each having a different frequency response and each responsive to a gain adjustment (34a-34d) A control signal (26) reflecting a particular zoom ratio is used in the adjustment of the gain applied to the filter sections, thereby proportioning the output of each filter section so that the combined output tracks the zooming process

Layered air filter medium having improved efficiency and pleatability

Abstract: A filter and method for making the filter. The filter has a first filter layer of high efficiency melt blown filter medium having an efficiency of pre-HEPA to HEPA, and a second filter layer of cellulose support medium by which the first filter layer is supported. The filter is pleated, and a plurality of dimples for separating a plurality of pleats can be fabricated on the pleat tips.

High-return-loss narrowband all-fiber bandpass Bragg transmission filter

Abstract: An all-fiber narrowband transmission filter (FWHM=0.25 nm) that is compact and exhibits high return loss (30 dB or better) is demonstrated using simultaneously written matched-pair, side-by-side Bragg gratings in a Michelson interferometer configuration. >

Multiple adaptive filter active noise canceller

Abstract: An active adaptive noise canceller (100) that does not require a training mode and operates over an extended noise bandwidth. The canceller partitions the noise bandwidth into frequency sub-bands, and multiple adaptive filter channels (120, 140) are employed, one for each sub-band, to cancel noise energy in the respective sub-bands. Each channel includes bandpass filters (121, 130) to restrict the channel to operation over only the particular sub-band, and delays are inserted in the operation of the filter weight updating. Because each channel is stable over its sub-band, the canceller operates over the extended noise bandwidth of all the sub-bands.

Voltage-mode notch, lowpass and bandpass filter using current-feedback amplifiers

Abstract: A voltage-mode filter employing three current-feedback amplifiers, two grounded capacitors and three floating resistors is presented. The proposed circuit offers the following advantages: realisation of notch, lowpass and bandpass signals from the same configuration, no requirements for component matching conditions, orthogonal control of ωo and Q, and the use of two grounded capacitors ideal for IC implementation, and low active and passive sensitivities and cascadability.

Linear periodic systems and multirate filter design

Abstract: We present a systematic procedure for the design of filters intended for multirate systems. This procedure Is motivated by viewing the equiripple design of filters in linear time-invariant systems as a process of obtaining optimum minimax filters for a class of bounded energy input signals. The philosophy of designing optimum minimax filters for classes of input signals is extended to multirate systems, which are not time-invariant. We develop a generalized Fourier analysis appropriate for linear periodic systems and use it to derive new error criteria for multirate filter design. Using such criteria yields optimum minimax multirate filters for the input signal class. The utility of our method is demonstrated by using it to analyze several multirate systems. We give numerical results on the design of a multirate implementation of a narrowband filter and compare our work to previous work on multirate filter design. Our numerical analysis is based upon a new formulation of the design as a semi-infinite linear programming problem. >

Curb inlet gravel sediment filter

Abstract: A portable curb inlet sediment filter which has a box filter frame and a primary baffle panel defining a filter chamber, to be filled with a particulate filter medium, such as gravel, for sediment removal, and an overflow chamber. The overflow chamber has at least one overflow baffle panel in order to provide a hydraulic opening and a peripheral end cap chamber. The end cap chamber is gravel filled in order to clarify water escaping around the front of the frame and into the hydraulic opening through the side panel. The filter frame and baffle panels are a mesh construction having apertures smaller in size than the particles of gravel to be contained.

An oil- and water-repellent gas-permeable filter

Abstract: A oil and water-repellent filter which contains a porous filter material that has its internal and external surfaces coated with a compound formed by combining a fluroropolymer having a fluorine-containing aliphatic cydic structure in the main chain and a fluoropolymer containing polyfluroalkyl groups. The coating imparts superior oil- and water-repellency without impaimnent to the flow of air or other gases through the filter.

Adaptive, global, extended Kalman filters for training feedforward neural networks

Abstract: Finding methods for the optimization of weights in feedforward neural networks has become an ongoing developmental process in connectionist research. The current focus on finding new methods for the optimization of weights is mostly the result of the slow and unreliable convergence properties of the gradient descent optimization used in the original back-propagation algorithm. More accurate and computationally expensive second-order gradient methods have displaced earlier first-order gradient optimization of the network connection weights. The global, extended Kalman filter is among the most accurate and computationally expensive of these second-order weight optimization methods. The iterative, second-order nature of the filter results in a large number of calculations for each sweep of the training set. This can increase the training time dramatically when training is conducted with data sets that contain large numbers of training patterns. In this paper an adaptive variant of the global, extended Kalman filter that exhibits substantially improved convergence properties is presented and discussed. The adaptive mechanism permits more rapid convergence of network training by identifying data that contain redundant information and avoiding calculations based on this redundant information.

Counterfeit document detection apparatus

Abstract: A document processing apparatus (10) incorporates a counterfeit detection system for identifying counterfeit suspect documents (22) on the basis of the magnetic characteristics of the documents (22). Each document (22) is transported within the vicinity of a magnet read head (86), which produces an electronic signal (210) in response thereto. The signal (210) from read head (86) is conditioned by a conditioning circuit (110) to be compatible with an analog-to-digital converter (304). The conditioning circuit (110) includes one or more amplifiers (130), a filter (140), a rectifier (160) and an integrator (180). The conditioned signal (220) from the integrator (180) is provided to the analog-to-digital converter (304) and is optionally limited to a compatible voltage level. As each document (22) is detected, a plurality of sampled values are obtained by the analog-to-digital converter (304). The sampled values are accumulated to produce one or more cumulative values (242, 274, 292, 404, 412) representative of the document (22). The cumulative values are compared with one or more predetermined reference values (263, 264, 276, 280, 282, 288, 402, 406, 410, 414) associated with a genuine document (22) in order to determine whether the detected document (22) is a counterfeit suspect document (22).