Showing papers on "Filter (video) published in 1969"

Adaptive filtering

Abstract: Applications of the Kalman filter in orbit determination problems have sometimes encountered a difficulty which has been referred to as divergence. The phenomenon is a growth in the residuals; the state and its estimate diverge. This problem can often be traced to insufficient accuracy in modeling the dynamics used in the filter. Although more accurate modeling is an obvious solution, it is often an impractical, and sometimes an impossible, one. Model errors are here approximated by a white, Gaussian noise input, and its covariance (Q) is determined so as to produce consistency between residuals and their statistics. In this way, realtime feedback is provided from the residuals to the filter gain. Onset of divergence produces an increase in the filter gain and the adaptive filter is able to continue tracking. This scheme has a probabilistic interpretation. Under certain conditions the estimate of Q produces the most probable finite sequence of residuals.

Acousto-Optic Tunable Filter

Abstract: Electronically tunable lithium niobate optical filter utilizing collinear acousto-optic diffraction in anisotropic medium

Overflow oscillations in digital filters

Abstract: The cascade and parallel realizations of an arbitrary digital filter are both formed using second order sections as building blocks This simple recursive filter is commonly implemented using 2's complement arithmetic for the addition operation Overflow can then occur at the adder and the resulting nonlinearity causes self-oscillations in the filter The character of the resulting oscillations for the second order section are here analyzed in some detail A simple necessary and sufficient condition on the feedback tap gains to insure stability, even with the presence of the nonlinearity, is given although for many desired designs this will be too restrictive A second question studied is the effect of modifying the “arithmetic” in order to quench the oscillations In particular it is proven that if the 2's complement adder is modified so that it “saturates” when overflow occurs, then no self-oscillations will be present

A step-by-step active-filter design

Abstract: This article presents, in a simplified manner, a design method for active filters intended for those who are not filter specialists. By following the described five-step approach, a circuit designer who has some knowledge of passive filters will (without having to learn a whole new technology) be able to design active filters just as easily as he now handles conventional passive filters. Starting with the filter specification, it is shown sequentially how to realize a network that meets the prescribed requirements. Configurations and element values are given for the low-pass (LP), bandpass (BP), high-pass (HP), all-pass (AP), and band-elimination (BE), second-order active filter building blocks.

Electronically tunable acousto‐optic filter

Abstract: Experimental results on a new type of electronically tunable optical filter are described. Tuning from 7000 to 5500 A has been obtained by changing an acoustic driving frequency from 750 to 1050 MHz. A band pass of less than 2 A, a corrected peak transmission of 50%, and an average skirt rejection ratio of about 45 dB have been obtained.

A comparison of roundoff noise in floating point and fixed point digital filter realizations

Abstract: A statistical model for roundoff noise in floating point digital filters, proposed by Kaneko and Liu, is tested experimentally for first- and second-order digital filters. Good agreement between theory and experiment is obtained. The model is used to specify a comparison between floating point and fixed point digital filter realizations on the basis of their output noise-to-signal ratio, and curves representing this comparison are presented. One can find values of the filter parameters at which the fixed and the floating point curves will cross, for equal total register lengths.

Anti-laser optical filter assembly

Abstract: A filter assembly for selectively removing preselected individual emission lines of laser energy from the visible spectrum comprising at least one pair of Fabry-Perot type filters which transmit laser energy emissions for dissipation in the filter assembly and reflect harmless radiation for transmission through the assembly. A plurality of these filter assemblies parallelly juxtaposed are also used to provide a filter screen for protection against laser energy emissions.

On a deterministic theory of estimation and control

Abstract: A feedback control system can be structured for linear nonstationary process and measurement systems comprising a deterministic filter whose output is the independent variable of a linear control law. Subject to uniform controllability and observability, the filter and control gains can be specified to provide arbitrary and separable stability properties. If the filter gain is selected to produce a stabilizing effect on the state estimate, and the control gain is selected to produce a stabilizing effect on the process, the filter and control gains are shown to satisfy matrix Riccati differential equations. This suggests the use of stochastic optimal control theory when there is no quantitative measure of optimality, but it is desirable to assure the qualitative property that feedback be stabilizing. A concise derivation of the Kalman-Bucy filter is included in an appendix to illustrate the facility of approaching optimal estimation problems with the methods of stability theory.

Periodic-switching filter networks-a means of amplifying and varying transfer functions

Abstract: A technique of periodically switching filter networks makes continuously variable filter parameters possible; at the same time capacitor or time-constant multiplication is obtained. With this method the time constants are multiplied by the switching period to switch aperture-time ration. Because the aperture time is usually small compared to the switching period, the active elements can be shared. A typical first-order system is analyzed for its step and sine response by the difference equation method. Phase and gain error expressions are established as a function of the various parameters. Limiting cases are then investigated to give a measure of a pulse- switched system performance. Finally an application of a multiplexed system is presented where three independent transfer functions are realized using one operational amplifier.

Digital modified discrete fourier transform doppler radar processor

Abstract: A system for processing data from Doppler radar returns including a sample and hold circuit, an A/D converter and scratchpad memory which holds the binary data for insertion, on a return-by-return basis, into a main MOS memory. The data is orthogonally extracted from the main memory on a range-by-range basis, each range group or cell being delivered to a digital filter. The binary data is converted to binary logarithm form for addition to a log coefficient weighting function to perform a multiplication in the filter. The filter is a modified discrete Fourier transform filter which acts as a bandpass and eliminates images and clutter. The filtered data is again stored and then converted to analog form for video displays.

Means for audible detection of the activation of a filter for smoking devices

Abstract: The present invention provides means for creating audible evidence of the activation of a filter by the rupture of crisp or brittle material included in a filter having rupturable fluidcontaining bodies therein.

Ventilated smoking article

Abstract: The admission of outside air to a tobacco smoke filter is enhanced by providing a corrugated wrapper around the filter plug, thereby to define a multiplicity of passages for conducting air admitted through the tipping paper over a relatively large portion of the surface of the filter plug.

Combination dual-flow and two-stage filter

Abstract: An oil filter for internal combustion engines has filter elements of two different flow rates arranged in parallel so that in general the high flow rate material acts as a full flow filter and filters oil going to the bearings and the low flow rate material acts as a bypass filter and filters oil that is returned to the crankcase. Automatic modification of this general dualflow arrangement and control of flow through the low flow rate material is provided by orifice means that connects the outlet sides of the two filter elements. This means includes a hole that is controlled by a one-way valve which prevents flow from the high-flow outlet side to the low-flow outlet side but permits it in the reverse direction and may also include an open bleed hole.

The Determination of Optimum Gate Lengths for Time-Varying Wiener Filtering

Abstract: The response function of a time-varying filter changes with the output signal, or observation time. Most existing time-varying filter techniques involve the empirical division of a seismic trace into a number of gates (or time windows) of given length, and a time-invariant filter is determined for each such gate. Few treatments have dealt with analytical methods to establish the gate lengths according to some optimum criterion.This paper describes a technique for the determination of optimum gate lengths. It is based on the work of Berndt and Cooper, which is here applied to the calculation of time-varying Wiener filters. The Berndt and Cooper technique produces an upper bound for the mean-square error between the true and a given approximated time-varying correlation function. The minimization of this upper bound leads to a relation which enables one to establish gate lengths directly from the input trace. Thereafter, ordinary time-invariant Wiener filters can be computed for each gate. The overall filtered trace is obtained in the form of a suitably combined version of the individually filtered gates.Experimentally it is shown that, with the Berndt and Cooper technique to determine optimum gate lengths, time-varying Wiener filters can be better than a time-invariant filter.

Filter having direct and cross-coupled resonators

Abstract: A band-pass filter is constructed from arrays of resonant elements which are coupled in a manner enabling control to be simultaneously effected over the filter''s amplitude and group delay characteristics. In each array the resonators are directly coupled in consecutive order and the resonators in one array are cross coupled to resonators in the other array. The direct and cross-coupled arrangement of resonators is in accordance with a mathematical relationship which permits selection of the filter''s group delay characteristic and the filter''s amplitude characteristic. In accordance with that relationship, multiple paths of different lengths are provided for the wave energy travelling from the input to the output.

Sharp-cutoff low-pass filters using floating gyrators

Abstract: The practical realization in gyrator-C form of a seventh-order Cauer-parameter low-pass filter with 40-dB stopband attenuation is described. The three floating coils of the equivalent LC filter were replaced by capacitor-loaded semi-floating gyrators. The gyrators were realized in hybrid form using thick-film resistors. The performance of the filter over a temperature range from -40/spl deg/ to +61/spl deg/C was very satisfactory, without any attempt at temperature compensation being made. This, together with the wider allowable element tolerances (compared with other active RC filter methods) shows the inherent suitability of gyrator-C filters for integration. Also in this paper some of the special problems and characteristics of gyrator-C filters are theoretically discussed, in particular the realization of gyrators with floating ports, gyrator Q-enhancement, and component tolerances in gyrator-C filters.

Filter for smoker's article

Abstract: A cigarette or cigar filter assembly having a large entry surface area in respect to its volume and characterized by low pressure drop, high effectiveness, and a simple configuration which is adapted to economical mass production. The body of the filter assembly is made from a bed of filter material, preferably aggregate particles which are bound by a minor proportion of resinous binder material into a fixed relation to one another. The body, in spite of having significant structural rigidity, and a density substantially equal to the density of the active aggregate material alone in its loose bed or uncompacted form, characterized by a low pressure drop thereacross, and the aggregate material, in a preferred embodiment, is bound so as to have substantially none of its activity impaired by the binder. Smoke flow through the axial ends of the filter body itself is blocked off so that smoke enters the filter body around the large entry surface presented by the outer surface of the filter body, passes radially through the filter body, and is drawn through the opening lying at one end of the core and facing to the rear of the body. Preferably, the filter assembly comprises an outer cylinder forming the mouthpiece and an inner filter body in the form of a hollow body. An annular smoke chamber is defined between the outer surface of the body, the entry portion of the body, and inner surface of the mouthpiece, and the center or core of the body opens to the rear of the body. The method of manufacture of the filter body is easily adapted to extrusion or like continuous manufacture, as well as batch method manufacture. Preferred filter materials include activated charcoal and ion exchange resins in finely divided form. The entire filter assembly is preferably of the same cross-sectional area and configuration as the end of the cigarette, while the filter body itself is of reduced diameter in respect to the cigarette diameter. In some embodiments, the advantage of effective filtration and low pressure drop are achieved with the use of filter materials which need not be surface, or otherwise, active provided they are arranged to provide a flow pattern in accordance with this invention.

N-path filter using digital filter as time invariant part

Abstract: A time division multiplexed digital filter is used as the timeinvariant part of an N-path filter. The use of a multiplexed digital filter alleviates the problem of closely matching the transmission characteristics of each of the N-paths.

Automatic infusion brew maker

Abstract: An automatic infusion brew maker comprising a pair of reservoirs and a pair of heat pumps connected thereto. The two heat pumps are driven by a common electrical heating means. Water from the first reservoir is pumped into a removable steeping basket, passes through a filter and exits through an outlet below the steeping basket. Water from the second reservoir is heated and pumped directly to the steeping basket outlet, thus bypassing the material to be steeped.

Cleaning arrangement for bag filter

Abstract: A cleaning arrangement for a bag filter whereby a jet of compressed air is directed from a nozzle into the bag filter and on to a novel deflector which divides the air into a portion that passes axially and a portion that is deflected radially. The portion passing axially thereof increases the pressure within the bag to cause the walls of the bag to flex outwardly and dislodge the dust cake on the outer surface thereof. The portion of the cleaning air from the nozzle that strikes the deflector is deflected radially on to walls of the filter bag also causing the flexing action which is propagated down the length of the bag to reinforce the action of the air which passes centrally therethrough.

A digital filter for biological data.

Abstract: Low pass digital filters are very suitable for use on stored biological data. This paper discusses the characteristics of the ideal data filter and the digital approximation to such a filter. The use of this filter with biological data is shown.

The Design of Optimal Convolutional Filters via Linear Programming

Abstract: Computational algorithms are given for the design of optimal, finite-length, convolutional filters with finite-length input sequences. Design techniques are developed for minimum-weighted-mean-square-error filters (MWMSE), for minimum-weighted-absolute-error filters (MWAE), and for filters which minimize the maximum output error (minimax). It is shown that the coefficients of the MWAE and minimax filters can be obtained by using standard linear programming methods. Next, the problem of developing a filter whose function is to "sharpen" a particular input waveform is considered. The filter input sequence is assumed to be derived from a Ricker wavelet of the velocity type and the desired output is the Dirac delta function. Convolutional filters are developed for this problem using each of the three performance criteria described above. The output sequences of each of the three optimal filters are discussed. It is shown that the minimax filter gives significantly better discrimination than can be obtained from either the MWAE or MWMSE filters.

Controllable magnetooptical devices employing magnetically ordered materials

Abstract: A MAGNETICALLY TUNABLE INTERFERENCE FILTER INCLUDING MAGNETICALLY ORDERED MATERIAL AND MULTIPLE LAYERS FOR EFFECTING OPTICAL INTERFERENCE. TUNING IS ACHIEVED BY CAUSING A CHANGE IN THE INDEX OF REFRACTION IN THE MAGNETICALLY ORDERED MATERIAL. IN ONE EMBODIMENTS, A MAGNETICALLY ORDERED FILM IS SANDWICHED BETWEEN TWO HIGH REFLECTANCE MIRRORS EACH CONSISTING OF ALTERNATE FILMS OF HIGH AND LOW INDICES OF REFRACTION. THENET MACROSCOPIC MAGNETIZATION OF THE MAGNETIC LAYER IS VARIED TO TUNE THE FILTER SO THAT IT TRANSMITS DIFFERENT WAVELENGTHS OF LIGHT IN ACCORDANCE WITH THE MAGNETIZATION OF THE FILM. THE MAGNETO OPTICAL EFFECT MAY BE VARIED BY MEANS OF AN EXTERNAL MAGNETIC FIELD WHICH MAY ALSO BE SUPPLEMENTED BY AN ELECTRIC FIELD FOR FURTHER CONTROL OF THE MAGNETOOPTICAL EFFECT. (THIS EMBODIMENT MAY BE USED AS A BIDIRECTIONAL LIGHT DIRECTOR.) IN A SECOND EMBODIMENT, A TUNABLE REFLECTANE FILTER IS FORMED BY ALTERNATE FILMS OF MAGNETICALLY ORDERED AND DIELECTRIC. IN A VARIATION OF THE SECOND EMBODIMENT, THE ALTERNATE FILMS ARE BOTH OF ORDERED MAGNETIC NATURE BUT HAVE DIFFERENT MAGNETIC PROPERTIES. AN EXTERNAL MAGNETIC FIELD IS APPLIED TO THE FILTER TO TUNE IT SO THAT DIFFERENT WAVELENGTHS OF LIGHT ARE REFLECTED FROM THE FILTER. TWO OR MORE OF THE FILTERS OF THE FIRST OR SECOND EMBODIMENT MAY BE COMBINED IN TANDEM TO EXPAND THE DYNAMIC RANGE OF TUNING. IN A THIRD EMBODIMENT, A DIELECTRIC LAYER IS SANDWICHED BETWEEN TWO MIRRORS OF THE TYPE USED IN THE SECOND EMBODIMENT. WHEN THE NET MACROSCOPIC MAGNETIZATION OF SUCH A FILTER IS CHANGED, THE FILTER ACTS AS A VARIABLE BAND PASS FILTER. ANOTHER EMBODIMENT IS A LIGHT BEAM SCAANNING OR DEFLECTING DEVICE INCORPORATING A MAGNETICALLY ORDERED MEDIUM RESPONSIVE TO A CONTROLLABLE MAGNETIC FIELD.

Interference filter with alternately designed pairs of dielectric layers

Abstract: This filter comprises a plurality of superimposed layers in which layers of a first material having a first index of refraction alternate with layers of a second material having a second index of refraction, thereby defining a plurality of high-index-low-index pairs of layers, and at least some high-index-low-index pairs of layers having a first optical thickness alternate with at least some high-index-low-index pairs of layers having a second optical thickness. Also described is an optimized design derived from this filter. Such filters can be formed by deposition of the layers on a substrate by calculating in advance the slope of the reflectance versus thickness curve that should be observed when each layer has its desired thickness and then, when forming the layers, by terminating the deposition of each layer when the slope of the reflectance versus thickness curve for the layer being deposited equals the calculated slope.