Showing papers on "Filter (video) published in 1968"

An approach to the implementation of digital filters

Abstract: An approach to the implementation of digital filters is presented that employs a small set of relatively simple digital circuits in a highly regular and modular configuration, well suited to LSI construction. Using parallel processing and serial, two's-complement arithmetic, the required arithmetic circuits (adders and multipliers) are quite simple, as are the remaining circuits, which consist of shift registers for delay and small read-only memories for coefficient storage. The arithmetic circuits are readily multiplexed to process multiple data inputs or to effect multiple, but different, filters (or both), thus providing for efficient hardware utilization. Up to 100 filter sections can be multiplexed in audio-frequency applications using presently available digital circuits in the medium-speed range. The filters are also easily modified to realize a wide range of filter forms, transfer functions, multiplexing schemes, and round-off noise levels by changing only the contents of the read-only memory and/or the timing signals and the length of the shift-register delays. A simple analog-to-digital converter, which uses delta modulation as an intermediate encoding process is also presented for andio-frequency applications.

Filter Design Using Transformed Variables

Abstract: A concise description is given of some recently developed filter design techniques. The discussion includes equal-ripple and maximally flat passband filters with general stopbands, as well as equal-ripple stopband filters with general passbands. To solve the approximation problem and to improve numerical conditioning, the design is carried out exclusively in terms of one or two transformed frequency variables. A step-by-step description is given for the design of each filter type; the steps are so formulated that the erosion of significant digits is minimized. The design processes given are unique and are directly suitable for automatic computer programs. Experience with such programs, using the algorithms described in the paper, indicates that filters up to about degree 30 may be designed using only single precision in the calculations. A discussion of some practical predistortion techniques, as well as a listing of available tabulated filter design information, is also included.

Composite coupled-mode filter

Abstract: An essentially two-dimensional electric-wave filter is formed by depositing a film of piezoelectric material upon a substrate and by applying input and output electrode pairs to different portions of the film. Each electrode pair together with the film and substrate form a composite resonator. The two composite resonators are located for a desired mechanical coupling between the two composite resonators. The filter may also consist of an array of n coupled composite-resonators having a common film and a common substrate and having the electrode pairs of two resonators of the array serving as input and output electrodes.

A Miniature High-Q Bandpass Filter Employing Dielectric Resonators

Abstract: The miniaturization of high-Q resonant microwave structures is of great importance. This must he done to keep pace with the size reduction of other related components. The need has led to an investigation into the feasibility of using dielectric materials as microwave resonators. This paper deals with the application of the TiO/sub 2/ dielectric resonator in a narrowband bandpass filter operating in the 2200 to 2300 MHz telemetry band. The study confirms the theory that a bandpass filter employing dielectric resonators is practical to build, is compact, and will approach the performance of an equivalent waveguide filter. The design employed five resonators mounted in a cylindrical tube that was 1.4 inches in diameter by 4.3 inches long and weighed 4.6 ounces. An equivalent waveguide filter would be approximately 2.3x4.5x16 inches long and would weigh approximately 64 ounces (WR-430). The thermal sensitivity of the dielectric resonator employing TiO/sub 2/ is an inherent problem and oven regulation for narrowband applications will be required. Small, inexpensive thermal jackets are available that will control the filter stability to a value equal to, or better than, that obtained with a filter utilizing aluminum cavities operating in a typical uncontrolled temperature environment.

Coffee brewing apparatus

Abstract: COFFEE BREWING APPARATUS USING A FILTER BAG WHEREIN MOVABLE PRESSURE PLATE CONFINES THE BAG WITHIN AN OPENTOPPED TRAY TO INSURE THROUGH DISTRIBUTION OF HOT WATER THROUGH THE GROUNDS IN THE FILTER BAG.

Pattern defect sensing using error free blocking spacial filter

Abstract: Defects in microcircuit patterns are sensed by illuminating the pattern with monochromatic collimated light. The illuminated pattern is imaged through a lens to produce substantially a twodimensional optical Fourier transform of the pattern at a plane on the output side of the lens. An optical filter (transparency) which includes substantially the negative of the Fourier transform of a defect-free specimen of the microcircuit is placed at the aforesaid plane to block the optical frequency components corresponding to the defect-free specimen. Light passing through the filter is processed to provide various indications of the pattern defects.

Zero crossings as a means of obtaining spectral information in speech analysis

Abstract: Zero-crossing patterns and spectral analysis using a filter bank are both a possible means in speech recognition for extracting information in the frequency domain that is useful in separating speech sounds. Results obtained from 60 speakers are given that show that the processing of segments of the 11 English vowels using a 13-channel filter bank give vowel separation comparable to that achieved with a 3-channel filter set followed by zero-crossing circuits. With prefiltering into 3 channels, zero-crossing patterns contain misleading and redundant information and it is shown that, by extracting only one zero-crossing distance during each pitch period, improved separation of low first formant vowels can be achieved with an economy in processed information. In vowels with closely spaced formants, both of which lie within the same analog filter band, the zero-crossing measure can give a mean of the two formant positions. The extent of spectral energy spread may be an important clue as well as its mean value, and a method is proposed for measuring it. In total, a much better understanding has been achieved of how filter-bank and zero-crossing analysis relate to each other and how best to extract zero-crossing information.

Filter and method of cleaning the filter

Abstract: A filter apparatus and method for cleaning a filter having at least one filter element with a separate container connected by a feed pipe to the outlet side of the filter apparatus and a stop valve in the feed pipe and means for causing a gaseous medium under excess pressure to displace a cleaning fluid from the container into the filter apparatus.

Apparatus for separating suspended solid particles from a carrier gas

Abstract: A filter chamber is superimposed on the container of a cyclone collector and vertically divided into two compartments by a filter bed of particulate material. A gas stream carrying solid particles is admitted to the cyclone collector, stripped of a portion of the solids, and passed to the upper compartment of the filter chamber by a conduit which passes the top wall of the container, the lower filter compartment, and the filter bed. Residual solid particles are removed from the gas stream passing downward through the filter bed and released from the lower compartment. A rake permits the filter bed to be stirred during regeneration by a scavenging gas passed upwardly through the filter bed.

Replaceable cartridge filter housing

Abstract: A replaceable cartridge is provided for a screw-on-type oil filter useful in automobile engines, or the like. A floating cartridge is provided which is spring loaded against the bottom of a housing and held in place by spider-type clamping arrangement which is easily removable for the changing of the filter therein. There is also provided an antidrainback valve which is constructed of a single piece and prevents oil from draining back into the oil system when oil is not being pumped through the filter. The filter housing is provided with a plurality of coolant fins which permits the oil to be cooled as it is being pumped through the filter system.

Universal digital filter for linear discrete systems

Abstract: A second-order recursive digital filter is disclosed for use as a universal building block in which a first summing means is provided for cyclically computing the function f(n) CX(n)+ 2( Alpha +2)f(n-1)-f(n-2)+ Beta 1(( Alpha +2)f(n-1)-f(n-2)) where X(n) is a sampled input signal in digital form, f(n-1) is the function f(n) delayed one computational cycle by a first unit operator and f(n-2) is the function f(n-1) delayed one computational cycle by a second unit operator. The coefficient C is a scaling parameter controlling the center-band gain of the filter. The coefficients Alpha and 2 together determine the center frequency of the filter passband while the coefficient 1 controls the bandwidth of the filter. The coefficient Alpha is limited to the values +1, 0 and -1 in order that implementation of a multiplier for the coefficient 2 may result in some cost savings. The product Alpha f(n-1) is then added to the product 2f(n-1). A second summing means is provided for cyclically computing the digital filter output in accordance with the following equation: Y(n) Aof(n)+ A1f(n-1)+ A2f(n-2) WHERE Ao, A1 and A2 are coefficients which control the ''''zeroes'''' of the filter response, and are set equal to +1, 0 and -1 respectively for a narrow-band digital filter. The coefficient 1 is set equal to zero for the filter to operate as an oscillator. A first order digital filter may be readily provided by modifying the first and second summing means to cyclically compute the functions f(n) CX(n)+ (n-1)+ Df(n-1) and Y(n) Aof(n)+ A1f(n-1), where D is a coefficient equivalent to Alpha +2+1.

The IBM 1975 optical page reader: part II: video thresholding system

Abstract: An adaptive video thresholding system is used in the Page Reader to minimize recognition failures due to contrast and line width variation. The main threshold operator is a linear function of the average contrast over a specified area. Adjustments to the threshold level are made by circuits that compute the average line widthin a character, and by circuits that filter out spatial noise in the vicinity of the character. The different types of print quality distortions predominant in typewriter printing and business machine printing are handled by switching between different sets of threshold operators.

Mold for making a filter

Abstract: A self supporting filter and a process for making a self supporting filter which process uses a mold arrangement that pinches the filter material adjacent each side of the mold cavity in which the molding material is to be injected to form the frame of the filter. Thus, the molding material flows from the runner around through the elongated cavity and impregnates the filter material inside the mold but the filter material is squeezed so tight adjacent each side of the cavity that the molding material cannot enter the filter material outside the cavity. Therefore, a frame having well defined edges is formed. The clearance between the mold parts that define the sides of the cavity, which pinch the filter material between the parts, can be in the range of an amount where the material is compressed to remove all voids to a point where the material would shear off. This clearance has been found to be sufficient that the molding material will not be pinched off nor damaged and at the same time plastic will not flash out into the form.

Filter cassette and holder therefor

Abstract: Filter cassette which basically includes a base frame composed of a bottom and extending sides from a portion of the perimeter of the bottom to form a chamber for receiving a precut filter. The bottom has means which aids in supporting the filter within the chamber and aids in permitting the fluid to drain from the underside of the filter. The base frame also has means upon it for mounting a resilient retaining frame. The retaining frame has a central opening and is adapted to be resiliently mounted upon the base frame. The base frame and the retaining frame cooperate to retain the filter between them in the chamber while permitting fluid to pass through the filter. A holder is provided to support the cassette during the filtration process.

X-ray fluorescence measuring system employing balanced x-ray filters and circuit means to vary the effective relative transmission thereof

Abstract: An X-ray fluorescence analysis system for measuring the amount of a specific element in a matrix containing variable amounts of other elements. The system employs a pair of balanced filters and a detector and counting apparatus. One filter has an absorption edge above the characteristic X-ray energy of the specific element and the other has its absorption edge below that energy. The apparatus is arranged so that with one filter in place the number of rays received by the detector for a time Tau is accumulated and with the other filter in place the number of rays detected for a fraction F Tau of that time is subtracted from the first number, the difference representing the quantity of specific element present.

Prediction of Filter Performance

Abstract: A method for the prediction of granular filter performance is presented, based on the analogy of filtration to the statistical chi-square distribution. The successful application of the method is illustrated by use of the experimental data of a number of different workers. An apparatus consisting of three thin depth filters is proposed to collect the data necessary for the performance prediction.

Digital MTI radar filters

Abstract: This paper discusses digital filters for moving-target indicator (MTI) radars. The digital MTI filter, implemented with video storage and cancellation, avoids the shortcomings of traditional analog filter systems and offers several important advantages, including freedom in the choice of the interpulse period. Several digital filter systems are described in detail.