Showing papers on "Offset (computer science) published in 1990"

A low-offset spinning-current hall plate

Abstract: An offset-reduction method for Hall plates has been developed which minimizes the influence of the stress and the temperature on the offset. The new method uses only one single symmetrical Hall plate in which the direction of the current is made to spin by contact commutation with steps of π/6 radians or smaller. The consecutive Hall voltages are averaged over time and the offset cancels out. The residual offset is about a factor of 10 less than that specified for commercially available silicon Hall plates and is limited by inhomogeneities in the plate.

Method and apparatus for high speed object location

Abstract: A method and apparatus for rapidly locating a desired object in a bit-mapped or vector display listed object space, wherein additional information is appended to or stored with the object information. This additional information relates to the relative coordinate position of that object or object element within a larger, more coarsely defined object space grid, such as an 8×8 grid. The apparatus and method of the present invention reduces the processing time necessary to locate the desired object within the object space by comparing the object and display area information relative to the grid for rapid preliminary acceptance or rejection prior to further detail search for the object or object elements. Thus, if no coincidence is found between the elements of the grid having at least a portion of the desired object and a second set of a grid elements corresponding to the desired display area, then the object is not located in the display area and further search in the corresponding grid portion of the object area is avoided. Similarly, signals relating cumulative object grid information are stored in linked memory lists, wherein comparisons between the display area grid information and the cumulative grid information contained in the linked display lists memory will eliminate the need to search that portion of memory should there be no coincidence, thereby enhancing the speed of object search.

CMOS amplifier with offset adaptation

Abstract: An integrated circuit amplifier having a random input offset voltage is adaptable such that the input offset voltage may be cancelled out. An inverting input node is a floating input node and is coupled to a source of input signal by a first capacitor. A second capacitor is connected between the output of the amplifier and the floating node. An ultraviolet window above the second capacitor allows the floating node to be charged, by the application of ultraviolet light, to a voltage which effectively cancels the input offset voltage. The ultraviolet window and capacitor electrodes are arranged such that the ultraviolet light may strike only the desired areas of the structure.

Dual-Hall ferrous-article-proximity sensor

Abstract: A ferrous article proximity sensor package includes a dual Hall element IC chip mounted at the end of a magnet. The axis of the chip, defined as being orthogonal to the chip face and equidistant the two Hall elements, is coaxial with the outer wells of the package but spaced away from the axis of the magnet. That exact position is such that the resulting difference in magnetic field strength at the two Hall elements is just enough to compensate for all the other factors that lead to an unwanted offset voltage in the sensor output. This package is made of two mating parts, one containing the magnet being eccentric with respect to the chip axis and the other containing the chip just above one magnet pole end. To achieve the abovedescribed desired offset condition in manufacturing, the one package part is simply rotated with the magnet relative to and within the other package part until the desired condition is met, and the two parts fastened together in that position.

Tightly coupled, low overhead RAM built-in self-test logic with particular applications for embedded memories

Abstract: RAM Built-In Self-Test logic is presented that utilizes a linear feedback shift register (LFSR) to generate data. Preferably, an LFSR is also utilized for address generation during memory self-testing. More than one cycle is implemented with offset of successive data sequences relative to address sequences to increase fault coverage. Memory storage is utilized in the data generation to enable a reduced area of the data generation circuitry.

Remapping defects in a storage system through the use of a tree structure

Abstract: A method and apparatus are disclosed for mapping a logical address generated by a device seeking access to a storage media into a corresponding physical address to create the appearance that all good addresses consitute a continuous defect free address space in the storage medium. A tree structure is created based upon known defective addresses in the storage medium. The upper levels of the tree are selectively loaded with decisional criteria which are employed to branch downward to an offset value stored in the lowest tree level. The respective offset value is added to the logical address to produce the desired physical address of the storage media for access. The tree is traversed each time an address is presented to map the requested logical address into a physical address corresponding to a location in the storage device for access. The media thus appears to the requesting device to be a continuous defect free address space with defective addresses congregated at the end of the address space, thereby avoiding the need for the requesting device to fragment files due to media defects.

Shaft alignment checking method

Abstract: A method for checking the coaxial alignment of tandem-arranged shafts involving the detection of a coaxial in-line or an offset state of the said shafts. In different angular positions of measurement two independent signals are produced related to any parallel offset and any angular offset of the shafts respectively. In the known methods the angular positions of measurement are bound by a mutual angular spacing of 90°. This leads to problems if there are obstructions in these angular positions of measurement of the device used for measuring. The method in accordance with the invention makes possible alignment checking operations using freely selectable angular positions of measurement.

Algebraic and Numerical Techniques for Offsets and Blends

Abstract: We examine some techniques and results from algebraic geometry, and assess how and to what extent they are of use in computer-aided geometric design (CAGD). Focusing on offset and blending surface construction, we illustrate how to apply and assess algebraic methods. We also examine some numerical techniques for interrogating offsets and blending surfaces constructed using the algebraic approach.

Self-intersection of an offset surface

Abstract: A method is described for obtaining the self-intersection curves of a collapsed offset surface. The method comprises two essential processes. The first is to detect the self-intersection points of a collapsed offset surface by successive unidimensional searches. The second is to calculate self-intersection curves by numerical integration by using some of the points obtained in the first process as initial points. All offset surface data needed is directly generated from the original surface without offset approximation. This method is applied to some collapsed offset surfaces whose original surfaces are defined by a B-spline.

Fifo memory system

Abstract: A FIFO memory system for buffering data between two data buses includes a RAM memory (12), write and read pointer registers (14, 16), an offset generator (16), a programmable offset register (20), and a comparator (22). The write pointer register (14) stores the address of the next data element to be written into the RAM memory (12), and the read pointer register stores (16) the address of the next data element to be read from the RAM memory (12). The offset generator (18) compares the contents of the registers (14, 16), and generates at an output thereof an offset signal representing the amount of memory space occupied. The programmable offset register (20) provides a programmed offset signal. The comparator (22) compares the offset signal and the programmed offset signal, and provides a ready signal when the offset signal is greater than or equal to the programmed offset signal. In one embodiment, the addresses stored in the write and read pointer registers (14, 16) are encoded in a minimum change code such as Gray code.

Optical disk device eliminating offset of actuator and offset eliminating method used thereby

Abstract: An optical disk device for eliminating an offset of an actuator which controls a fine adjustment of a tracking control. In the device, during an offset measuring mode, an electric drive current of the actuator is changed and the drive current is stored and held when a detection output at a neutral position in a position detector of the actuator is obtained. Then, during a usual operation mode, the obtained offset current is constantly supplied as the drive current of the actuator, whereby a spring force is cancelled and an offset of the tracking error signal is eliminated.

Method and apparatus for improved seismic prospecting

Abstract: An improved method and apparatus for conducting seismic prospecting is provided wherein more accurate estimates of the source wavelet can be achieved. Receivers (202) detect pulses at vertically offset locations. The pulses are converted to digital signals in a signal processor (212) and stored on a recorder (210). A processor (108) operates on the stored signals to produce an output wavelet A'(107 ,θ) in accord with the equation ∫(P.G n -G.P n )dx g .

Linearized differential amplifier

Abstract: Disclosed is a linearized differential amplifier, comprising connecting input terminals and output terminals of the differential pairs(16) respectively in parallel; arranging N sets of differential pairs(16)(where N is an integer of 3 or more); an offset voltage(17) generating circuit for supplying different and equivalent offset voltages to the respective differential pairs(16); a circuit(18) for weighting these output currents; and a circuit(19) for adding the output currents. Particularly, the offset voltage generating circuit and the weighting circuit carry out equivalent weighting of the offset voltages and the output currents so that change of the differential output current corresponding to change of the differential input voltage shows an equal ripple characteristic. Moreover, to give equivalent offset voltages to the respective differential pairs(16), a linearized differential amplifier where emitter areas in respective differential pairs(16) are different is disclosed. In this case, the ratio of emitter areas is 1 2: 7.872983 and 1:1 when N is 3, and 1:13.40261 and 1 : 2.030215 when N is 4.

Method and apparatus for analog D.C. offset cancellation

Abstract: The present invention utilizes a decision feedback equalizer (DFE)/finite impulse response filter. A plurality of taps of the equalizer supply coefficients to the input function and are updated in a feedback loop. An additional DC tap is provided, with a constant value as its input source. Within reasonable limits, the constant term (i.e. D.C.) in an analog input signal is subtracted out by the action of the constant value DC tap. The coefficients are updated by a decision feedback means such that phase, amplitude and DC offset may all be corrected. In the preferred embodiment, the filter is a T/2 spaced filter in which two samples per baud are utilized by the filter. The filter outputs a complex word which is coupled to a quantizer. The actual constellation locations are compared to the ideal locations in a difference block so that offset errors may be detected. The difference signal is used to update the coefficient values. One of the coefficients so generated is the DC tap in the filter. The product of the modified tap value and the constant input term is combined with the convolutional sum of the input signal to remove constant terms resulting from DC offset in the input signal.

High resolution absolute encoder for position measurement

Abstract: An encoder comprises a rotatable or longitudinally displaceable body having a plurality of sawtooth-shaped regions which lie one behind the other in the direction of rotation or displacement. Each sawtooth-shaped region is separated by a steep edge that extends transversely to the direction of rotation or displacement. Upon movement of the body due to its sawtooth-shaped configuration, the distance of the surface of the sawtooth-shaped regions changes relative to a distance sensor arrangement. An evaluation circuit receives the output signals of the sensor arrangement and determines the rotation angle or the displacement of the body. The sensor arrangement comprises two distance sensors being offset relative to one another in the direction of movement by less than one sawtooth-shaped region forming distance signals, with the distance signals input to the evaluation circuit. The evaluation circuit evaluates only one of the distance signals in order to determine the angle or displacement of the body. The entire surface of the rotationally or longitudinally displaceable body facing the distance sensors has coinciding sawtooth-shaped regions. A rough measuring system is provided whose signals are fed to the evaluation circuit to characterize the individual sawtooth-shaped regions. An offset signal which characterizes the rotation angle or the displacement is associated with the individual sawtoothshaped regions in the evaluation circuit. The absolute rotation angle or displacement signal is formed in the evaluation circuit from the applicable offset signal and the signal of the presently employed distance sensor.

Optical disk recording and reproducing apparatus

Abstract: An optical disk recording and reproducing apparatus in which during coarse access, an adjustable target speed is obtained using a speed offset value stored in a speed offset memory. The speed offset value being determined between a plurality of reference velocities and a plurality of adjustable offset velocity values. The system also performs fine access within a defined distance from the optical head to the designated track upon completion of the coarse access mode. The speed offset values are continually updated by to improve the accuracy of the coarse access operation saving overall access time.

Offset frequency multipoint modem and communications network

Abstract: In a multipoint data communications system used with analog communications channels that may insert undesirable frequency offsets in a modem carrier frequency, a slave modem that adjusts its transmit carrier frequency compensates for the offset influenced communications channel. A central modem device does not have to train up to slightly offset frequencies when the communications channel is effectively removing the offset added by a slave modem at its transmitter site.

Acquiring a best focus using a focus signal offset

Abstract: A focus acquisition system includes providing a focus offset and changing the offset symmetrically for each measurement cycle. The amplitudes of the readback or tracking error signal are sensed and compared. When the amplitudes of the tracking error or readback signal is different at each of the offsets, then a new measurment cycle is performed after calculating a new offset value. The process is repeated until the temporary measurement offsets result in readback amplitudes that are substantially equal. A best focus is then indicated as being a position in which small defocussing will not substantially degrade the quality of the readback signal.

An Algorithm Producing Balanced Partitionings of Data Arrays

Abstract: We present a new polynomial time algorithm for allocating array elements to the processor memories of parallel computers. The algorithm produces, for sufficiently large arrays, partitionings that are balanced, near-rectangular and near-bulky. Balanced means each allocation is assigned the minimal number of elements. Near-rectangular means that each allocation is at most two off from the optimal aspect ratio in each dimension and has at most two jogs along each edge. A jog is where the boundary deviates from a straight line. Near-bulky means that each allocation has a near maximal ratio of interior/exterior points. For an I x J array of points and a K x K array of processors the algorithm produces balanced nearbulky partitionings when I, J 2 4K and produces balanced, near-bulky and near-rectangular allocations when I, J 2 8K. These bounds are not tight. A variant of the algorithm produces allocations with at most six neighbors per allocation for arbitrary stencils. Using these near-rectangular allocations incurs little additional cost for compilers for distributed memory parallel computers, and the extra run-time cost usually is offset by the advantage of balanced allocations.

Three dimensional cellular communication system with coordinate offset and frequency reuse

Abstract: A three dimensional cellular communication system comprising a plurality of cells arranged in a multi-level environment to reduce interference and improve frequency reuse in both horizontal and vertical directions by offsetting cells stacked on different levels of the multi-level environment.

Analytical computer-aided machining system and method

Abstract: A computer-aided machining system is described which implements a method of geometrically-intersecting offset surfaces and drive surface to automatically generate tool control paths. Preferably, the machine tool is controlled by characterizing the shape of the part to be milled using the mathematical representation, and from that mathematical representation calculating an approximate offset surface for the surface to be milled. The approximate offset surface is compared with the drive surface for the machine tool to define an approximate tool control point curve. The actual tool control point curve is then calculated by comparing the approximate tool control point curve with the mathematical representation of the surface of the part. The actual tool control point curve can then be supplied to a machine tool to enable it to mill the part surface.

Offset frequency stabilization of RF excited waveguide CO/sub 2/ laser arrays

Abstract: A close-packed array of waveguide lasers provides an offset frequency which is inherently more stable than that from independent devices, and permits difference frequency tuning based on the tilting of a common resonator mirror. Examples are given for two- and three-channel arrays. Passive stability of the beat frequencies between channels generated by this tuning method is shown to be good, and for two channel arrays was further enhanced by using an electronic stabilization loop. A simple model of the control loop is formulated to express the relationship between the loop parameters and resultant improvement in frequency stability. The model parameters are compared to experimental results through Allan variance measurements. An Allan variance minimum of 20 Hz has been achieved for the two-channel system and areas for further improvements are considered. >

An adaptive offset cancellation technique for adaptive filters

Abstract: Offset may be introduced in the adaptation process in certain implementations of adaptive filters. The adaptive filters. The adaptive filter still converges with the offset, however, to nonoptimal tap weights with excess mean square error. Here, an offset cancellation technique, also adaptive, is proposed. A set of new taps is introduced to counteract the offset. The convergence of this adaptive cancellation technique is demonstrated analytically and by using computer simulation. >

Roots blower with improved clearance between rotors

Abstract: A Roots blower has two rotors in which each of said rotors, as viewed in plan view thereof in the direction of the rotational axis thereof. The rotor has a center and orthogonal short and long axes and has a final shape of a contour offset from a basic profile curve by an offset distance at every point thereof in the normal line direction thereto. The offset distance is also determined in accordance with a function which assumes a maximum value when the angle between a line connecting the rotor center with the point and either of the short and long axes is 45 degrees, which assumes a minimum value when the line coincides with either of the short and long axes, and the function comprises an exponential power of a sine function.

Head positioning control apparatus for a data storage device

Abstract: In a servo system for a hard disk drive, an integrating circuit for eliminating an offset of a head has its capacitor charged to an extent corresponding to an offset amount, at a time of a track following control operation, before an integral action is done. The integrating circuit performs the integral action through the utilization of the charged capacity to eliminate the offset amount of the head. A CPU retrieves an initially prepared offset table for one of voltage level data corresponding to the offset amount which is determined in accordance with a head's destination track. A D/A converter converts the voltage level data which comes from CPU to a voltage and supplies it to the capacitor in the integrating circuit.

Optical writing device

Abstract: PURPOSE:To perform the fine control of the offset of a belt with simple constitution by providing a control means which fetches signals from a belt offset correcting means, a driving means, and a beam detecting means, detects the displacement in the width direction of a belt-like photosensitive body and controls the belt offset correcting means. CONSTITUTION:Since the quantity of a beam cast to a photosensor 10 is changed according to the position of the belt-like photosensitive body 1, the output current of the photosensor 10 is changed. This current value is changed to a voltage value. When the voltage value is higher than a reference voltage value, it is judged that the photosensitive body 1 is deviated in a direction shown by an arrow I. The control part operates the displacement and drives a motor 13 through a motor driving circuit based on the result of arithmetic operation. When the motor 13 is driven, a screw part 14 is rotated and the parallelism of a belt offset correcting roller 4 with a driving roller 3 is changed, so that the displacement in the axial direction of the photosensitive body 1 is corrected. Thus, the fine control of the offset of the belt is performed with the compact and simple constitution.