Abstract: A comparator circuit, for a switched resistive network which may be combined with a transconductance amplifier, simultaneously and independently compares a plurality of input voltages to a reference voltage. The circuit comprises a current splitter having a current input, a plurality of comparator outputs, and a corresponding plurality of voltage inputs that control the fraction of the input current available at each comparator output. A reference output of the current splitter is provided as an input to a current mirror, and each of the comparator outputs of the current splitter is connected to a corresponding output of the current mirror. The current available at each of the current mirror outputs is a function of the reference input provided from the current splitter. The comparator circuit needs only one bias input and one reference input. The inclusion of a second biasing device with an associated mirror device produces a transconductance amplifier combined with the comparator circuit.

Abstract: A III-V semiconductor device is provided with a ballasting resistor that may be connected in series with the emitter, collector, or base of an HBT, depending on the function of the device. The semiconductor ballasting resistor is formed in the subcollector epitaxial layer that is in intimate thermal contact with the substrate. The resistor is defined by isolating a rectangular area of the subcollector with ohmic contacts at each end and is fabricated with no processing steps in addition to those required for the HBT. The resistor provides self-limiting current capacity because of its semiconductor nature. Connected in series with the HBT emitter, the semiconductor resistor prevents destruction of the HBT, particularly in multiple cell, high power applications.

Abstract: Conventional Boolean Logic Control is augmented to provide enhanced diagnostics, monitoring, and fail safe operation for dynamic systems having distributed discrete-valued sensors and actuators. A decentralized model of a controlled system defines behavior and timing models for both sensors and actuators, termed Control Elements (CEs). Each CE has a first model for transition from state 0 to 1, and a second model for transition from state 1 to 0. Each behavioral model is defined by an Event Signature comprising a sequence of state changes in neighboring CEs. A continuous evaluation of event signatures is performed to compute a probability that a given CE will change state. An Expectation Function is used to check and enforce the correct behavior of a CE. A statistical temporal model predicts delays in the states of a CE as a function of its previous and current delays.

Abstract: A traffic signal network is controlled by an adaptive, fuzzy logic based, distributed system of microprocessors. The system can control multiple intersections in a network of two-way streets. Traffic signal timing at each intersection is be defined by signal control parameters such as cycle time, phase split, and offset time. Local traffic flow data is input to each microprocessor and characterized by membership functions. Fuzzy logic decision rules are applied to the characterized data and used to adjust the signal control parameters at each intersection as a function of the local traffic conditions and the signal parameters in effect at neighboring intersections. Cycle time is adjusted to maintain a good degree of saturation, and phase split is adjusted to achieve similar degrees of saturation on competing approaches. The offset time at each intersection is coordinated with the neighboring intersections and adjusted gradually to optimize traffic flow in the dominant direction.

Abstract: A low cost, real time vehicle lane position detection system is provided for determining and maintaining the position of the vehicle on a highway. The system comprises an image sensor mounted on the front of an automotive vehicle and an integrated processor for performing real-time lane mark detection. The sensor/processor system identifies highway lane marks on the detector image plane by using a nonlinear resistive network for detecting outliers. A line detection algorithm, such as the Hough transform, is used to determine the lane marks from the outliers on the image plane. Because the expected lane position can be determined in advance, an added degree of signal-to-noise discrimination is achieved by providing feedback to the processor for outlier detection. The position of the vehicle in the lane is determined and tracked from the position of the detected lane marks on the image plane given the sensor position and optical geometry.

Abstract: A swirl flow microwave plasma torch is provided for the growth of diamond films. The swirl flow torch incorporates an injection nozzle that directs reactant gases into a cylindrical flow tube extending through the center of a tuned microwave cavity. The outer surface of the nozzle comprises a contoured, conical shape that causes inert gas, directed tangentially against the outer surface of the nozzle, to swift in a helical path that surrounds and confines the reactant gas emerging from the nozzle. The tuned cavity is coupled to a microwave energy source to generate a highly localized plasma in the reactant gas in the center of the sheathing swirl of inert gas. The swirl of inert gas contains the plasma in a well-defined shape, prevents in-diffusion of undesirable gases, forms a boundary layer to prevent plasma migration, and provides flow tube cooling. The reactant gas flow forces the plasma out of the flow tube to form a plasma flame that can be impinged on a substrate to induce diamond growth.

Abstract: A method is provided for removing residual amounts of oxygen and water vapor from the controlled atmosphere of an enclosed chamber. A small volume of high-purity silicon is heated in a crucible placed inside the chamber. The silicon is typically heated with a power source separate from that used for heating the chamber and its primary contents. The heated silicon functions as an effective oxygen getter for removing residual oxygen and water vapor from the controlled atmosphere before and/or during a process conducted in the chamber. Heating the silicon to a molten state can induce beneficial convective stirring that keeps the silicon surface fresh for effective, efficient, and continuous capturing of oxygen.

Abstract: A high temperature resist process is combined with microlithographic patterning for the production of materials, such as diamond films, that require a high temperature deposition environment. For diamond films, a high temperature silicon nitride resist can be used for microlithographic patterning of a silicon substrate to provide a uniform distribution of diamond nucleation sites and to improve diamond film adhesion to the substrate. A fine-grained nucleation geometry, established at the nucleation sites, is maintained as the diamond film is deposited over the entire substrate after the silicon nitride resist is removed. The process can be extended to form surface relief features, such as "moth eye" surfaces, and microstructures of fine-grained polycrystalline diamond, such as rotatable microgears and surface relief patterns, that have the desirable characteristics of hardness, wear resistance, thermal conductivity, chemical inertness, anti-reflectance, and a low coefficient of friction.

Abstract: A pulsed diode ring laser gyroscope and method of modulation are provided to greatly reduce the occurrence of frequency locking in optical gyroscopes at low rotational rates. One or two optical diodes serve as optical amplifiers for a pair of counterpropagating optical pulses circulating in an optical ring resonator. The amplifiers are driven twice each round trip (once for each pulse) using pulses much shorter than the round trip time. The short optical pulses overlap in regions of the resonator generally isolated from light scattering elements. The pulses are produced by gain switching the optical amplifiers with an electrical current pulse train having a fundamental period synchronous with the optical round trip time in the resonator cavity. With this modulation scheme, the diodes can be thought of as gates that open twice each round trip-once for each of the counterpropagating pulses. During each on time, the diodes amplify only a clockwise or counterclockwise pulse.

Abstract: A solid state joint and a method of making a solid state joint between aluminum or magnesium alloys is provided. The joint consists of a diffusion bond with unmelted pieces of a fragmented foil dispersed along the diffusion bond. The joint is made by placing a friable foil between the parts being joined and pressing the parts together to crack the foil. The assembly is then heated and pressed together for a sufficient time, temperature, and pressure to cause the aluminum or magnesium alloy to flow into the cracks, across the foil, and then to diffusion bond together. The foil is made from a material which is harder than the alloy being joined and which will not melt at the bonding temperature.

Abstract: A monolithic integrated circuit provides RF and DC coupling for a unit cell of a high power quasi-optic grid amplifier. The monolithic chip includes two heterojunction bipolar transistors (HBTs) connected in a differential pair configuration with a common emitter and integrated collector-base and emitter bias resistors. Each of the plurality of unit cells comprising the quasi-optic grid amplifier includes an emitter-coupled HBT differential pair chip at the center, an input antenna that extends horizontally in both directions from the two base leads, an output antenna that extends vertically in both directions from the two collector leads, and high inductance bias lines for the emitter and collectors. The grid amplifier, which functions as a high frequency, high gain, wide bandwidth, free-space beam amplifier, comprises a plurality of unit cells arranged in a repeating pattern of input and output dipole antennas.

Abstract: An apparatus and method are provided for transmitting two-dimensional images through a single mode optical fiber. Light from a broadband source is dispersed into component wavelengths, spatially modulated to contain an image, collected for multiplexing in a single mode optical transmission fiber, transmitted through the single mode fiber, and demultiplexed into its component wavelengths to reproduce the transmitted image. The two-dimensional dispersing and collecting elements may be realized using thin film channel waveguides having arrays of optical gratings. Because the dispersive element at the receiving (output) end of the transmission fiber must reproduce the dispersal pattern used at the source, the information transmitting device may be used for data encryption and decryption.

Abstract: An optical device is provided for detecting the degree of obscuring moisture or precipitation on the windshield of an automotive vehicle. A source of light, such as a light emitting diode (LED) or a laser diode, is positioned to illuminate the windshield. An optical imager and detector array senses light emitted by the source, either transmitted or reflected by the windshield, and imaged on the array. The light source and detector may be positioned in convenient, out-of-the-way locations inside or outside the windshield. When the windshield is free of obscuring precipitation, light from the source is imaged on a sensor of the array aligned with the optical axis of the imager. When obscuring moisture or precipitation is present on the windshield, light is scattered such that significant portions are imaged on sensors off the optical axis of the imager.

Abstract: An electronic circuit is provided for comparing a plurality of input signals and indicating and/or selecting the maximum or minimum signal from the input set. The plurality of input signals are amplified, logarithmically compressed, and buffered by a corresponding plurality of simple transistor circuits, which are substantially identical. The buffered input signals are provided to a high resolution multiple input comparator circuit. The comparator circuit comprises a two-stage emitter-coupled comparator and a single stage inverter-amplifier. In the first comparator stage, strong input signals share the bias current but all the weak signals drop out. The inverter-amplifier stage amplifies the differences between the strong signals that survive the first comparison stage. The second stage comparator determines the strongest of the few remaining signals.

Abstract: A system is provided for regenerating reducing agents used in ancillary chemical or electrochemical processes such as restoring solderability of electronic components. The system includes a cathode, an anode, and an electrolyte system that is separated by a semipermeable ionic barrier into a catholyte and an anolyte. The catholyte includes the reduced member of a redox couple, which can be regenerated electrochemically. The redox couple of the electrolyte system is charged like a battery and discharged during the ancillary process. Regeneration of the reduced member of the redox couple is accomplished at the cathode. The cathode comprises an electrode having a high hydrogen overvoltage so that sufficiently negative potentials can be attained while minimizing hydrogen evolution. Chemical balance is maintained by the semipermeable ionic barrier, which permits proton migration from the anolyte to the catholyte but acts as a barrier against diffusion and migration of cations from the catholyte to the anolyte.

Abstract: A method is provided for fabricating metal matrix composites. Optical or reinforcing fibers, which may be in the form of monofilaments, mats, or tow, are consolidated into a metal matrix alloy. Grooves may be provided in the metal matrix material for holding and positioning the fibers. A transient liquid diffusion bonding agent in the form of a powder may be blended with powdered filler material, such as powdered matrix material, to provide a vehicle for consolidating the fibers into the metal matrix. The fibers and the blended powder are placed between layers of the metal matrix material and the whole structure is heated under minimal pressure to liquefy the bonding agent. The liquid bonding agent wets each fiber and interdiffuses with the matrix material, resulting in rapid isothermal solidification of the alloy and consolidation of the fibers in the matrix.

Abstract: An electrical circuit provides a constant phase shift between two output signals derived from a common input. The output signals are designed to provide a constant phase shift at constant amplitude over a very large frequency range. The common input is provided to both a non-shift channel and a phase-shift channel. The non-shift channel comprises a fixed attenuator circuit that provides a non-shifted output signal. The phase shift channel comprises a low-pass RC filter circuit that provides a phase shifted output signal. The two output channels are connected by a transformer phase detector that generates an error signal. The error signal is input to an operational amplifier that provides a phase-shift control signal to the RC filter circuit of the phase-shift channel.

Abstract: In a Ce-ZrO.sub.2 -based laminar composite having enhanced fracture toughness, alternating barrier layers comprise a ceramic material that undergoes stress-induced phase transformation, if any, less readily than Ce-ZrO.sub.2. Separation of the barrier layers is normally in the range of about 10-200 .mu.m, with optimum individual barrier layer thicknesses at the lower end of the range. Powders of ceramic materials comprising the individual layers of the composite are dispersed in separate slurries. The pH of the slurries is adjusted to form coagulations in which the particles settle without mass segregation and can be consolidated to high density by centrifuging. After centrifuging, the supernatant liquid can be removed and a desired volume of another slurry can be added on top of the first layer of consolidated material. This process can be repeated indefinitely to form a consolidated structure having individual layers as thin as approximately 10 .mu.m.

Abstract: Holographic apparatus and methods are provided for generating high resolution telescopic images using low cost, small aperture lenses. Holographic media, such as photorefractive crystals, are used in conjunction with multiple and/or synthetic aperture techniques. In a multiple aperture system, a thin nonlinear holographic medium is used with a plurality of small optical lenses to compensate for the inherent piston and tilt errors of the lenses, thereby providing higher resolution. In another embodiment, synthetic aperture techniques are accomplished by illuminating a far field object with coherent light, deriving a reference beam from the coherent light, and changing the position of the reference beam in accordance with a computational formula. A hologram is formed from a sequence of image exposures in the holographic media, each made at different positions with respect to the image.

Abstract: A method is provided for joining Be-Al alloy structural members to yield a high shear strength at the interface. Surface oxides are first removed from the Be-Al alloy members. Aluminum is then selectively etched from the bonding surfaces to allow the flow of braze alloy into high aspect ratio capillary sites. A discontinuous ceramic reinforcing material, such as Al.sub.2 O.sub.3 or SiC in particulate or whisker form, is added in small quantities to a braze foil, such as Al-Si, to create a composite at the bond interface. The braze foil and reinforcing material are sandwiched between the Be-Al alloy members, and the joint is heated to above the liquidus temperature of the braze alloy but below the melting point of aluminum. The resulting interface shear strength of the Be-Al alloy bond has been tested to an average of about 60% of the parent alloy shear strength.