Showing papers by "Hewlett-Packard published in 1974"

Bridging and Stuck-At Faults

Abstract: The commonly used stuck-at fault fails to model logic circuit shorts. Bridging faults are defined to model these circuit mal-functions. This model is based on wired logic which is a characteristic of many logic families such as resistor-transistor logic (RTL), diode transistor logic (DTL), emitter-coupled logic (ECL), etc. It does not apply to TTL circuits. The model also limits to fan-out-free leads.

High-speed integrated logic with GaAs MESFET's

Abstract: The feasibility of using GaAs metal-semiconductor field-effect transistors (GaAs MESFET's) in fast switching and high-speed digital integrated circuit applications is demonstrated. GaAs MESFET's with 1-/spl mu/m gate length are shown to have a current-gain-bandwidth product f/SUB T/ equal to 15 GHz. These devices exhibit a 15 ps internal delay in a large-signal switching test. A simple logic circuit consisting of MESFET's and Schottky diodes was monolithically integrated on a semiinsulating GaAs substrate. This logic circuit exhibits a propagation delay of 60 ps with no output load, and 105 ps when its output is loaded by three similar logic gates. A useful bandwidth of approximately 3 GHz is observed.

Miniaturized magnetic card reader/recorder for use in hand-held calculator

Abstract: A miniaturized card reader/recorder is specified which is activated by the thickness of the card itself and in which actuating mechanism the card is simultaneously conformed to the contour of the magnetic read/record head.

In-line reflective lead-pair for light-emitting diodes

Abstract: A plurality of flat, subminiature, reflective in-line lead pairs for light-emitting diodes is contained in a frame. Each lead pair has a flat mounting surface for the diode chip. Although the diode chip is mounted on one of the lead pairs, the deep reflector for side-emitted light is formed from both leads of the pair. The reflector configuration provides for mounting semiconductor chips in addition to the diode chip therein. The reflector also precludes an illuminated light-emitting diode from inadvertently illuminating one or more adjacent light-emitting diodes.

Optimum crystal orientation for acoustically tuned optical filters

Abstract: Theoretical and experimental studies of the acoustically tuned optical filter show that suitable crystal orientations can be divided into two broad classes based on the acoustic properties of the propagation path used. In acoustically isotropic cases, the acoustic phase and group velocities are collinear. All 32 crystalline point groups are examined for acoustically isotropic orientations that may be useful in tunable optical filters. In acoustically anisotropic cases, the phase and group velocities are not collinear. Methods are presented with which the effects caused by acoustic divergence in these cases may be compensated by similar effects due to changes of birefringence. In particular, anisotropic propagation collinear with acoustic group velocity on a path 101.2° from the optic axis in the Y, Z plane of quartz allows operation at a lower acoustic frequency and power level than that required by isotropic orientations for equivalent performance.

Device for synthesizing frequencies which are rational multiples of a fundamental frequency

Abstract: A frequency synthesizer is disclosed which can provide frequencies which are rational multiples of a fundamental reference frequency. The synthesizer includes a voltagecontrolled oscillator in a phase-locked loop with the reference frequency. A modulo-N counter is included to allow synthesis of harmonics of the reference frequency. To obtain rational fractional frequencies between harmonics a ''''cycle swallower'''' is provided to occasionally abruptly shift the phase of the oscillator output. The swallowing rate is determined by the contents of a storage register which is pre-loaded with a representation of the desired frequency. The contents of this storage register are periodically loaded into and accumulated in an accumulator which generates an overflow signal to the cycle swallower whenever the accumulated value exceeds its maximum storage capacity. In response to the average rate of phase shifting by the swallower, the loop stabilizes when the oscillator frequency is equal to the desired rational multiple of the reference frequency.

Dislocations in vapor phase epitaxial GaP

Abstract: Dislocations in VPE GaP grown on (100) oriented LEC GaP substrates have been characterized, and their origins and effects on LED performance have been investigated. In non-nitrogen doped epilayers, the dislocations are found to originate in the substrate and propagate through the epilayers in straight lines in [100] and directions. The dislocation density of the epilayer is found to be nearly equal to that of the substrate. Introduction of nitrogen during growth of the epilayer has been observed to bend these so-called “inclined≓ dislocations propagating through the layer into [0−1 1] directions in the (100) plane and thus produces segments of [0 −1 1] dislocations to relieve the lattice parameter mismatch due to N. The mismatch dislocation density is observed to be proportional to the N doping level. At very high N doping levels, > 1019 cm-3, a large number of new inclined dislocations are observed, which may be in part due to GaN precipitation. The effects of dislocations on LED properties were investigated by measuring dislocation densities in the individual diodes using the electron beam induced current mode of the SEM and comparing this with the spot brightness and luminous flux. The dislocations were observed to produce dark spots in the EL emission in many cases. For a series of runs where all growth and processing parameters were fixed, a good correlation between B/J and dislocation density was observed with B/J decreasing with increasing dislocation density in the range < 1 × 104 cm−2 to 1 × 106 cm−2.

Acoustic surface wave oscillator force-sensing devices

Abstract: An acoustic surface wave oscillator is employed as a force-sensing device. Dual acoustic surface wave oscillators coupled to a single substrate of piezoelectric material which inversely change their respective frequencies in response to a force applied normal to the surface of the substrate comprise a high-sensitivity, temperature-compensated force-sensing device. The outputs of the oscillators are applied to an electronic mixer circuit to produce a difference frequency output signal which is a function of the applied force. Other configurations utilizing the force-sensing properties of acoustic surface wave oscillators are disclosed.

Thermal printing head

Abstract: A high density thermal printing head includes resistive heating elements on a layer of silicon which is epitaxially grown on a sapphire substrate. Isolation diodes are diffused into the silicon layers and in accordance with various embodiments of the invention, transistor decoding circuitry, logic control and other circuitry may also be diffused therein. To facilitate the arrangement of the heater elements in an array without the necessity of numerous layers of metallic interconnections, portions of a layer in the silicon are doped with impurities to serve as highly conductive interconnections between various elements on the head. These interconnections are crossed beneath other metallic interconnections on the surface of the silicon to provide the electrical crossings necessitated by the physical arrangement of elements on the head. In some embodiments, the diodes and/or transistors are diffused into mesa-like regions of the silicon in direct communication with heater elements overlayed on the mesas.

Apparatus and method for testing digital circuits

Abstract: A device is disclosed which converts a digital signal or bit stream into a digital signature repesentative of the digital signal by means of a feedback shift register. The apparatus may be used to identify and characterize digital signals at various test points in an apparatus for testing purposes. Signatures for digital signals from properly operating circuits can be recorded in a variety of fashions for later comparison with signatures of digital signals from circuits under test. The comparison of the signatures enables a person using the apparatus to determine whether the circuit under test is operating properly and, if it is not, to locate the fault in many instances. The apparatus may also be used to examine digital signals to enable identification of transient errors.

Adaptable programmed calculator having provision for plug-in keyboard and memory modules

Abstract: An adaptable calculator is provided by employing five MOS/LSI circuits interconnected by a multiple line bus system. They include (1) a read-only memory circuit group in which subroutines for performing arithmetic and other functions of a basic keyboard input unit are stored; (2) a control and timing circuit for scanning the keyboard, for retaining status information relating to the condition of the calculator or of a particular subroutine, and for generating a next address in read-only memory; (3) an arithmetic and register circuit containing an adder, a group of working registers, a group of data storage registers forming a stack, and a constant storage register; (4) a data storage circuit which provides ten data storage registers, nine of which are employed by the calculator system and one of which is available to the user for storing data; and (5) an input/output (I/O) circuit for enabling the calculator to communicate with various I/O peripheral units such as a typewriter and an X-Y plotter, for performing binary arithmetic by means of a binary arithmetic logic unit contained therein, and for performing various system housekeeping operations. Input and output units include a keyboard input unit having a receptacle for accommodating a 15-key function block to enlarge the capabilities of the calculator and an 18-column output printer unit for printing intermediate results of calculations, entered data, arithmetic operators, and diagnostic notes. An optional 15-digit seven-segment light emitting diode (LED) output display unit may be inserted into the calculator mainframe. All of these input and output units are included within the calculator itself. An X-Y plotter, a typewriter, a marked sense card reader, an extended data storage memory, a magnetic card reading and recording unit, a ASCII bus for enabling the calculator to communicate with data gathering instruments, and many other peripheral input and output units may also be employed with the calculator. The calculator may be operated manually by the user from the keyboard input unit or automatically by a program written in user-level language and stored in a plug-in read-only memory unit (ROM), a plug-in programmable read-only memory unit (PROM) or a read/write memory unit associated with a plug-in magnetic card reading and recording unit.

Recent Approaches To Computer - Generated Holograms

Abstract: Computer holography is a subject of interest to a small but increasing number of researchers. This paper briefly describes the concept and history of computer holography, how it works, and its possible applications. Also presented are the recent approaches to computer holography developed at Stanford University, and a procedure for synthesizing this new class of computer holograms. These new on-axis holograms are very efficient both in their use of reconstruction light and in their use of display resolution elements during synthesis. They keep the advantages of the kinoform, a previous approach by IBM, but do not have its limitations. One approach makes use of color reversal film, such as Kodachrome II. Another approach only requires phase-transmittance material, but preserves both amplitude and phase information. Experimental results are presented.

Stress effects in acoustic surface-wave circuits and applications to pressure and force transducers

Abstract: Delay time changes in a quartz acoustic surface-wave delay line subjected to mechanical stresses have been obtained as variations in frequency of a corresponding ASW delay line oscillator. A simple cantilever structure was found to have the largest sensitivity to stress. Applications to a force and pressure transducer will be described.

A multiminiprocessor system implemented through pipelining

Abstract: Several recent and proposed computer systems have employed parallel and pipelined architectures to increase instruction execution rate, or throughput. These vary from the giant ILLIAC IV1 with its large number of processing elements constrained to perform nearly identical computations in unison (single instruction stream-multiple data stream9) to the Carnegie-Mellon C. mmp system2 employing a number of independent minicomputers with shared memory (multiple instruction stream-multiple data stream). On the other hand, pipelining has been used in numerous' large computers, such as the Control Data 6600, 7600, and STAR, the IBM System 360/91 and 360/195, and the Texas Instruments ASC, to improve throughput. These systems generally employ single instruction stream-single data stream processing, although some machines in this category also have “vector” instructions that operate on multiple data streams.

Chemically Vapor Deposited Polycrystalline-Silicon Films

Abstract: In recent years polycrystalline silicon deposited by chemical vapor deposition has become of importance in many semiconductor applications. The formation and properties of films deposited for different applications are reviewed in this paper, and the use of the films in semiconductor devices is discussed. The deposition temperature, gases, and impurities are found to have the major influence on the properties of the films. These deposition variables significantly affect the crystal

Method and apparatus for enhancing and maintaining character quality in thermal printers

Abstract: The quality of thermally printed characters is enhanced by controlling the time at which and the time for which power is applied to the resistive printing elements in a battery-operated moving-head thermal dot matrix printer. By sequentially strobing the elements in the pattern of the character to be formed as the print head moves across thermal sensitive paper, a high-quality slanted character is printed and parasitic losses are reduced. By inversely varying the time power is supplied to each dot as battery voltage varies, character quality is maintained and useful battery life is extended.

Two channel test instrument with active electronicphase shift means

Abstract: A network analyzer is provided with an electronically variable phase shifter in the IF portion of the reference channel, and the phase shifter is connected to sweeping signal generator (sweeper) driving the device under test. As the output frequency of the sweeper changes, the control signal to the phase shifter changes the phase shift in the IF portion of the reference channel, compensating for phase differences between the test and reference signals due to different line lengths in the two signal paths. The electronically variable phase shifter may comprise a linear phase shifter such as a phase lock loop along with a frequency mulitplier and down converter to multiply the phase shift produced by the phase shifter.

Inverse/complementary function prefix key

Abstract: A hand-held programmable calculator is specified, which has a prefix key for designating the inverse or complement of direct functions having legends on the keyboard thereof, thus expanding the utility of the keys on the keyboard.

Variable-frequency interferometer resonance filter

Abstract: An apparatus for measuring the absorption index of a flowing liquid includes a measuring cell and a reference cell. Each cell is formed in the space between and confined by the reflectors of an interferometer of the spherical Perot-Fabry type. The cells are located in parallel in a common body and by means of a common piezo-electric tuning element the distance and thus the resonance frequency of each pair of reflectors can be uniformly varied in order to establish the resonance condition for each liquid in the cells. The voltage supplied to the piezo-electric tuning element for establishing the resonance condition is indicative of the relative absorption index of the liquid under test. The reference cell serves to compensate for unwanted disturbances by changes in temperature, in the flow rate and the like.

Photon isolator with improved photodetector transistor stage

Abstract: A photon isolator device wherein the photon emitter and photodetector are matched such that the photodetector and transistor unit can be fabricated utilizing standard integrated circuit monolithic isolation techniques resulting in a high efficiency, high speed photon isolator; one preferred emitter utilizes GaAs(1 x)Px with x ranging from .20 to .48. A special technique is employed to provide a buried layer under the photodetector region that increases the collection layer depth. The elements in the integrated circuit transistor gain stage are formed so as to provide temperature compensation to balance the temperature dependence of the emitted light of the photon isolator. A novel plastic film insulation is utilized to mount and space the emitter and the photodetector elements of the photon isolator.

Multiconfiguration ionization source

Abstract: This is an ion-producing source having a distinct chemical ionization configuration and a distinct electron impact configuration. In this source, a hollow chamber including an ion source and a source of sample molecules receives a hollow, slidable cylindrical member having a chemical ionization chamber within it. Orifices in the chamber and the cylindrical member connect the chemical ionization source chamber to the electron source and to the sample molecule source when the cylindrical member is pulled to one position. When the cylindrical member is pulled to another position, the slidable cylindrical member and the inside walls of the chamber define the ionization region to which the electron source and the sample molecule source are directly connected. By moving the cylindrical member, the ionization source can be changed from a chemical ionization source to an electron impact source.

Linked list encoding method and control apparatus for refreshing a cathode ray tube display

Abstract: LINKED LIST DATA ENCODING METHOD & CONTROL APPARATUS FOR REFRESHING A CATHODE RAY TUBE DISPLAY Abstract of the Disclosure Data is configured in 8 bit control characters and 8 bit data characters and stored in a terminal random access memory as a linked list structure. Control apparatus accesses the data stored in the terminal memory in 16 character blocks and identifies the accessed information as representing figures to be displayed, video enhancement features, or program execution path changes. Each two character link provides an address pointer to the next 16 character block of data and control information. The first character block of a line of displayable figures has links to the previous displayable line and the next line of characters to be displayed. The control apparatus combines internal hardware functions and the linked list encoding structure as implemented by program logic to provide display and control character identification, data access address modification, video display enhancement and selection of alternate character sets.

Display apparatus having improved cursor enhancement

Abstract: A non-interlaced raster-type display includes interface circuitry for displaying character patterns indicative of data signals manipulated by a processor under the control of a manually-operable keyboard. The displayed character patterns are enhanced by half-shifting or delaying a raster line of display signals for a given character in order to improve the legibility of displayed alphanumeric character patterns. A blinking pointer or cursor is manually movable via keyboard control to the character spaces desired and the blinking cursor display is inhibited during movement thereof in order to maintain an invariant display of the cursor during repositioning.

Startable phase-locked loop oscillator

Abstract: A startable oscillator is provided whose frequency can be locked to a reference frequency and whose initial phase at the instant of start can be maintained indefinitely with a known precision. More particularly, the frequency of a tunable oscillator is locked to the reference frequency by means of a phase-locked loop. When a start signal is applied to the loop, the tunable oscillator is momentarily stopped and then restarted a fixed time later with a new phase as a result of the interruption. Simultaneously the inputs to a phase detector in the loop are withheld so that the phase detector will not produce any error correction signal to retune the frequency of the oscillator as a result of the change in oscillator phase. Large variations in the frequency of the tunable oscillator which would destroy the initial phase information are therefore avoided. Although the signals to the phase detector input are withheld from the phase detector, they are monitored and adjusted in phase. At an appropriate time at which the phases resemble the conditions prior to the start/restart interruption, the inputs are released to the phase detector. The phase detector thus experiences only locked conditions both before and after the restart. After the restart, however, the loop is locked at the new phase of the oscillator. The phase-locked loop thus behaves as though no interruption had occurred so that the tunable oscillator will continue operating at a frequency locked to the reference frequency but having the new phase preserved indefinitely.

Differential drive rotating disc impact printer

Abstract: A drive system is provided in which a pair of fixedly mounted motors imparts simultaneous and independent rotational and translational motion to a disc such as a print disc containing a character font. By means of a belt and pulley system, different rotations of the two motors produce different combinations of rotational and translational motions of the disc. The system may also drive elements other than a disc, e.g., a bar and pen arrangement such as that typically employed in an X-Y plotter. A related mechanical system is also disclosed in which translational motion of a pair of rack gears provides simultaneous and independent rotation and translation to a pinion gear. The driving translational motion may also be supplied by a pair of independent belt drives moving parallel or antiparallel to each other.

Fabrication of thick film resistors

Abstract: A glass material is deposited upon a ceramic substrate and then fired at an elevated temperature in air. Screen printed resistor elements formed on the glass material are fired, lapped, and annealed.