Showing papers on "Filter (video) published in 1971"

New automatic equaliser employing modulo arithmetic

Abstract: The limitations of present automatic and adaptive equalisers stem from the use of feedforward transversal filters. These drawbacks may be obviated by using a feedback transversal filter, the inverse filter, but this is only suitable for limited use since it can be an unstable circuit. It is shown that modulo arithmetic may be used in the inverse filter to eliminate completely the possibility of instability, and a very simple automatic or adaptive equalisation system is presented. Some interesting properties of the modulo inverse filter are included.

Effect of finite word length on the accuracy of digital filters--a review

Abstract: The accuracy of a digital filter is limited by the finite word length used in its implementation. Techniques have been developed to analyze this problem. Good agreement between the theoretical and experimental results has been reported. This paper discusses some of these accuracy problems and reviews some of the approaches used in investigating them. The calculation of the statistical mean-squared error at the output of the filter is discussed in detail.

Digital filter for pcm encoded signals

Abstract: A digital filter either of a recursive or transversal type responsive to successive digitally encoded analog signal samples of m bits each. The filter comprises an accumulator for multiplying and summing a weighted hybrid value obtained from a memory medium addressed by a selected one of the m bits of each of N digitally encoded signal samples. If the bits of the N samples used for addressing the memory are derived from successive input signals only, then the filter is of the transversal type. If V of the N signals whose bits are used for addressing are from the input samples and R of the N signals whose bits also are used for addressing are obtained from filter output signals, then the filter is recursive. By addressing the memory with the binary value of like bit positions of the signal samples, then a hybrid value may be stored, which hybrid value need only be multiplied and combined by the accumulator. This permits the use of a substantially smaller memory than that required if the digits of the signals looked up the completed weighted function.

The Design of Multistage Separable Planar Filters

Abstract: A two-dimensional, or planar, digital filter can be described in terms of its planar response function, which is in the form of a matrix of weighting coefficients, or filter array. In many instances the dimensions of these matrices are so large that their implementation as ordinary planar convolutional filters becomes computationally inefficient. It is possible to expand the given coefficient matrix into a finite and convergent sum of matrix-valued stages. Each stage can be separated with no error into the product of an m-length column vector multiplied into an n-length row vector, where m is the number of rows and n is the number of columns of the original filter array. Substantial savings in computer storage and speed result if the given filter array can be represented with a tolerably small error by the first few stages of the expansion. Since each constituent stage consists of two vector-valued factors, further computational economies accrue if the one-dimensional sequences described by these vectors are in turn approximated by one-dimensional recursive filters. Two geophysical examples have been selected to illustrate how the present design techniques may be reduced to practice.

Real-Time Tracking Filter Evaluation and Selection for Tactical Applications

Abstract: Five important tracking filters that are often candidates for implementation in systems that must track maneuvering vehicles are compared in terms of tracking accuracy and computer requirements for tactical applications. A rationale for selecting among these filters, which include a Kalman filter, a simplified Kalman filter, an ?-s filter, a Wiener filter, and a two-point extrapolator, is illustrated by two examples taken from the authors' recent experience.

The Use of Linear Filtering as a Parameterization of Atmospheric Diffusion

Abstract: A simple linear filter is adapted for use in numerical models of the large-scale circulation to act in place of an explicit horizontal diffusion term in the equations. The filter can be shown to be ideally suited for this purpose in the sense that it can be made increasingly scale-dependent as the order of the filter is increased. The one-dimensional filter of order n is constructed from n three-point symmetrical operators and involves 2n/1 grid points. It is capable of eliminating two-grid-interval waves completely, yet allowing little or no damping of longer waves. In one space dimension, the use of the n = 1 order filter can be shown to be equivalent to the incorporation of a one-dimensional Fickian diffusion term in the differential equation. For any order n, the use of the one-dimensional filter is equivalent to the incorporation of a one-dimensional linear diffusion of order 2n. It is therefore apparent that as n increases, the ability of the filter to discriminate in its response to short-...

Optical low-pass filter

Abstract: An optical low-pass filter so formed that a rectangular wave phase grating including a plurality of sets of laminae for introducing phase retardation, in which laminae in each set being arranged in parallel with each other and the laminae of different sets being arranged to cross with an angle to each other is inserted in an optical system of the type having a color-encoding filter means disposed in the light path of the optical system for, such as, a single tube color television camera, and high frequency components of an objective image on the color-encoding filter means are attenuated less than a predetermined level, to the image focused on the color-encoding filter means, a degree of blur always larger than the value calculated from the grating period of the color-encoding filter means is given and another image focused on a position distant from said image as far as a predetermined distance brings about no interference to produce another color striped pattern with said color-encoding filter means, regardless of f-number of the objective lens and the diaphragm value so as to remove the influence effected by interference between the luminance and chrominance signal.

Electronic Tuning of a Dye Laser Using the Acousto‐Optic Filter

Abstract: Dye laser electronic tuning by inserting calcium-molybdenum oxide acousto-optic filter into cavity

An optimal tracking filter for processing sensor data of imprecisely determined origin in surveillance systems

Abstract: This paper develops a new optimal tracking filter that accounts for and minimizes the effects of correlation uncertainties in surveillance systems. This filter reduces to the Kalman filter in the limiting case of no correlation errors and infinite gate sizes, and provides substantially improved performance in environments wherein correlation uncertainties cannot be ignored.

Method for inspecting filters

Abstract: Method and apparatus are described for washing hollow cylindrical engine air cleaners or filter elements on inside and outside surfaces. After the washing operation and before drying the filters are inspected by directing a forceful flow of water heavily aerated with entrained bubbles of air against the filter surface. Visual observation of bubbles passing through the filter element provides rapid and reliable detection of leaks through the filter.

Optical low pass filter

Abstract: An optical low-pass filter which is inserted in an image forming optical system in order to attain the response to zero in a frequency over the cut-off frequency and which is adapted so that the response in said optical system may not undergo a change depending upon the variation of F-number of the optical system The filter gives a blur to all images formed by said image forming optical system, and is composed of phase elements provided on a transparent base plate The phase elements are disposed systematically on a base plate for giving the phase difference to the wave front of light ray incident upon said transparent base plate

Gain-sensitivity product-a figure of merit for hybrid-integrated filters using single operational amplifiers

Abstract: It is shown that a different measure of performance must be used to evaluate hybrid-integrated active filters from that used to evaluate active filters in discrete form. Where sensitivity was previously found to be an adequate and useful measure for Q stability of discrete active filters, the gain-sensitivity product gives an accurate measure of Q stability for hybrid-integrated circuits. Where negative feedback filter schemes were found to be preferable with respect to Q stability when realized in discrete form, positive feedback schemes with their very much lower gain- sensitivity product may be preferable in hybrid-integrated filter circuits. In addition, they require low-gain amplifiers than can be used up to higher frequencies. Q-stability measurements of hybrid- integrated positive feedback, or Sallen-Key-type circuits, which were realized with tantalum thin-film resistors and capacitors combined with beam-leaded operational amplifier chips agree very accurately with the predictions derived from gain-sensitivity calculations.

Electrically conducting filter media for fluids

Abstract: Conductive filter elements are made by treating nonconductive fibrous materials such as inorganic or organic fibers with resins containing finely divided carbon The treated fibers are then fabricated into filter elements which are electrically conductive throughout Strands of roving or yarn which are nonconductive may be joined by twisting together with strands of conductive roving or yarn to give conductivity to the finished multiple strand Conductive filter elements are also made from extruded fibers which are filled with carbonaceous material during extrusion These elements permit grounding of static electrical potential which would otherwise accumulate in a nonconductive element If desired, a controlled low potential direct or alternating electrical charge can be maintained on the filter element to enhance the separation of particles of opposite charge Particulate filter media, such as that used in filter beds, may also be treated with carbon to form an electrically conductive filter mass

Electrostatic air filter

Abstract: An air cleaner is provided comprising a filter assembly, an electrical power pack, and interconnecting high-voltage transmission means. The filter assembly is constructed of a filter unit having a prefilter and two layers of a dielectric filter media between which is sandwiched a positively charged grid. The filter assembly further includes a pair of negatively charged plates between which the filter unit is placed, and a header assembly molded of a rigid plastic and which is also provided with the male high-voltage receptacle and high-voltage contacts to the anode grid.

Optimal mismatched filter design for radar ranging, detection, and resolution

Abstract: In a multiple-target environment a radar signal processor often uses weighting filters that are not matched to the transmitted waveform. In this paper the mean-square range-estimation error, the detection Signal-to-noise ratio (SNR), and the effects of sidelobes are expressed in terms of the impulse response of an arbitrary mismatched filter. It is desired to find that impulse response that results in the minimum range-estimate variance subject to preassigned constraints on the side-lobes and the detection SNR. It is shown that for detecting the radar target and estimating its range, the form of the optimum filter is a modified transversal equalizer. If only detection is required, the optimum filter reduces to the transversal equalizer. Certain parameters upon which the solution depends can be found by solving a nonlinear programming problem. Numerical results are given for an interesting class of transmitted waveforms.

Structure of optimum receiving filters in data transmission systems (Corresp.)

Abstract: It has been observed by several authors that a number of different optimum receiving filters (corresponding to different criteria of goodness) for sampled-data transmission systems can be factored as a product of a matched filter and a periodic filter with the period equal to the sampling frequency. By a simple argument it is shown in this correspondence that any reasonable criterion of goodness will lead to an optimum filter that has this form.

Sintered filter having straight holes therethrough

Abstract: A sintered metal, or ceramic filter having parallel, straight holes of uniform diameter and with smooth inner surfaces passing therethrough is formed by sintering a green compact about a large number of straight wires arranged parallel to one another Upon application of heat at a sintering temperature above the melting point of the wire material and less than the melting point of the sintering powders, the wires are absorbed into the pores of the sintering powders and leave holes of the same shape and size as the original wires in the resulting sintered filter

Filter anti-drainback and relief valves

Abstract: A single molded rubber element provides both the relief valve and the anti-drainback valve in an automotive-type oil filter.

Plural-sample filter device

Abstract: A plural-sample filter device comprises a base plate, a filter plate, a cover plate, and a holding clamp for clamping the parts together with the filter plate interposed between the base and cover plates. The cover plate is formed with a plurality of openings for introducing the samples to be filtered, and the filter plate is provided with a corresponding plurality of aligned perforated areas each adapted to hold a filter disc. The base plate is formed with a plurality of receptacles aligned with the filteres, and is further formed with an outlet adapted to be connected to a pump, and a channel connecting the receptacles to the outlet.

Training adaptive linear filters

Abstract: Adaptive linear transversal filter is trained with a periodic training sequence having period exactly equal to the number of variable parameters of the filter to be set in the training mode. After training, tap coefficients may be cycled in a closed loop to a preferred position.

Random Processes for Earthquake Simulation

Abstract: Criteria presented for the evaluation of earthquake simulation processes relate to the autocovariance function, maximum acceleration response spectra, and nonstationarity of the process. Two previously used and two new processes are examined with respect to these criteria by means of theoretical and simulated results. The previous processes develop a nonstationary white noise for input to a linear filter and take the filter output as the simulated ground acceleration. They are identical except for filter properties. Neither of these processes complies with all the criteria. One fails to provide reasonable response spectra; the other produces an unrealistic ground-velocity variance function that does not disappear with time. The new processes incorporate weighting functions that produce correlated, nonwhite filter inputs. One of these produces response spectra with undesirable irregularities. The other, which employs an exponential decay-type weighting function, complies with all criteria and is recommended as a suitable model for earthquake simulation. Additional relationships are examined for rms and maximum oscillator response spectra.

Compressible disposable filter press for blood

Abstract: An open cell, compressed, elastic plastic foam filter medium, having average diameter cell pore openings selected values ranging from 25 to 150 microns, is disposed as a planar volume in a an adjustable disposable filter press. The filter medium is disposed between a pair of rigid filter press plates, which are in turn disposed in the filter press structure. The press can provide an adjustable control means suitable for varying the average diameter of the pore openings, by varying the compression of the filter medium. A flexible, filter press case provide means of assisting blood circulation through the filter medium, and of separating air entrained in the blood in the filter press.

Some design aspects concerning input filters for DC-DC converters

Abstract: Various DC-DC converter input filter requirements as applied in spacecraft power processing equipment, are reviewed with respect to the spacecraft, its power source and filter loads. The conflicting implications arising from the requirements are noted. A filter configuration capable of providing a satisfactory overall compromise is presented. Various design aspects for converter input filters are analyzed. These include minimum weight toroid inductor design, the possibility of non-linear oscillation developing through the interaction of an input filter and a negative impedance regulator and problems in using paralleled capacitors to supply switching regulator loads.

The Kalman-Bucy Filter as a True Time-Varying Wiener Filter

Abstract: The notion is exploded that to build a Kalman-Bucy filter, one needs to know the whole structure of the signal generating process. It is shown that the filter is constructible knowing precisely those covariances required to construct a Wiener filter, and no more, and that the filter is independent of the particular models of the processes generating these covariances. Performance of the Kalman-Bucy filter does depend on the models, however. Results are also obtained for the smoothing problem.

Prestressed filter media

Abstract: An improved fluid treating filter having a support frame disposed between at least two layers of filter media. The support frame is of unitary construction and bowed in a direction opposing the flow of a fluid. One layer of media is in communicative relation with the surface of the frame facing the flow of the fluid whereas the second layer is in communicative relation with the edges of the downstream surface of the frame and is in spaced relationship with the downstream surface. The filter may include a cover adaptable for outerfitting the filter wherein the cover has perforations for allowing the passage of the fluid therethrough.

Method of making an electromechanical filter

Abstract: A method of making an electromechanical filter of the type having a plate-shaped crystal and a plurality of metal coatings arranged on portions of the major surfaces of the crystal. The metal coatings are produced by applying first layers of metal, having accurately determined boundaries, to the major surfaces of the crystal and then applying additional overlays of metal to the surface or surfaces of the first layers in such quantity that the resonant frequency of the filter will equal a desired frequency.

Liquid crystal optical processor

Abstract: The optical processor employs a photoconductor-activated liquid crystal as a spatial filter to control transmissivity of coherent light through the processor. The liquid crystal filter pattern determines the pattern input to Fourier transform and can optionally also define the transmissivity of a Fourier processing filter. This permits near real time transform.

Air sampling device

Abstract: This disclosure relates to an air sampling device operated solely by compressed air which is conducted through a venturi tube thereby creating a region of reduced pressure for drawing ambient air into the device where particles or gases carried therein are trapped in a filter type device for analysis. The device includes a manifold having a plurality of fittings each adapted to receive individual sample-collecting chambers whereby several samples may be taken consecutively.

Make up mirror

Abstract: An electric make-up mirror having light sources which provide substantially uniform energy output through most of the visible region, which when used in conjunction with light filters will simulate specific lighting conditions such as daylight, office light (fluorescent), home light and evening light (incandescent). The light sources are comprised of special lamps which provide a unique degree of flexibility in that various lighting conditions may be simulated with a minimal loss of energy. The mirror is provided with two matching light sources, and two matching filter assemblies disposed on opposite sides of the mirror. The filter assemblies are adjusted by a single control mounted for the synchronous selection of a matching filter from each of the filter assemblies. The light filters of each filter assembly, when interposed between the light sources and the user, selectively vary the spectral energy distribution of the light transmitted from the light sources so as to simulate daylight, ordinary fluorescent light and incandescent light. The mirror allows the user to select the illumination approximating the type of light under which the user expects to be seen.