Showing papers by "Hewlett-Packard published in 1978"

A Practical Algorithm for Solving Dynamic Membrane Equations

Abstract: Many investigators work with the Hodgkin-Huxley model of membrane behavior or extensions thereof. In these models action potentials are found as solutions of simultaneous non-linear differential equations which must be solved using numerical techniques on a digital computer. Recent membrane models showing pacemaker activity, such as that of McAllister, Noble, and Tsien, involve solutions covering long periods of time, up to fisve seconds, and many ionic currents. Those added requirements make it desirable to have an efficient algorithm to minimize computer costs, and a systematic and simple solution method to keep the program writing and debugging to manageable levels.

Radiation-grafted hydrogels for biomaterial applications as studied by the ESCA technique.

Abstract: Electron spectroscopy for chemical analysis (ESCA) was used to study the surface composition of several radiation-grafted polymers in both the dry and hydrated (frozen at 160°K) states. Poly(2-hydroxyethyl methacrylate) (HEMA) and polyacrylamide, both hydrophilic polymers, were readily detected in the hydrated or dehydrated states when grafted to polyethylene substrates. For silicone rubber substrates, both grafts were observed on the hydrated surface but were significantly decreased in surface concentration upon dehydration. For grafts on a polyester-urethane, acrylamide was not a major constituent of either the dry or hydrated surface, while HEMA appeared to increase in abundance upon drying. The amount of the hydrophobic poly(ethyl methacrylate) found on the graft surface depended upon the substrate polymer used, but the surface abundance of poly(ethyl methacrylate) was not affected by drying. These results were considered in terms of polar group orientation, polymer chain mobility, substrate permeability, and the limitations of the ESCA technique. The implications of these results with respect to the use of radiation-grafted hydrophilic polymers for biomedical applications are also discussed.

Filter characteristics of codirectionally coupled waveguides with weighted coupling

Abstract: Filter-sidelobe suppression of codirectionally coupled optical waveguides with spatially tapered coupling strength is examined. The filter responses for several taper functions with low Fourier transform sidelobes are calculated, and the resulting channel densities when used for wavelength multiplexing are compared. For a 30 dB crosstalk level, all the taper functions considered yield at least a tenfold increase in the number of carrier channels over untapered filters. The filter response for a quantized taper that results from conventional fabrication procedures is also considered.

Breakdown mechanism in short-channel MOS transistors

Abstract: In this paper a new breakdown mechanism in a short channel MOS transistor is proposed based on experimental measurements of substrate currents. We have observed a negative resistance in the substrate current followed by conductivity modulation, similar to the operation of a unijunction transistor during switching. By adding an external substrate resistance, saturation of the substrate current was observed in conjunction with the turn-on of the parasitic NPN (source-substrate-drain) bi-polar transistor. Breakdown of the device will occur when the drain bias reaches BV CEO of this parasitic bipolar transistor. The channel length dependence of the breakdown voltage of the short channel MOS transistor can then be explained by the dependence of BV CEO on the base width.

Optically controlled two channel integrated-optical switch

Abstract: An integrated optical bistable device based on a waveguide directional coupler switch is demonstrated. The device has four optical ports, and the power incident on the two input ports exists from two distinct output ports so that all-optical data processing or remote optical switching can be performed. On/off ratios as high as 12 dB have been observed. A switching time of \sim300 \mu s and switching energy of ∼3 pJ have been achieved.

Resistance neutralizing system for electrochemical devices

Abstract: The net resistance of a circuit for utilizing an electrochemical cell is reduced by inserting negative resistance in the circuit that is slightly less than the inherent resistance of the cell, and means are provided for automatically adjusting the amount of negative resistance in response to the inherent resistance of the cell employed.

Double vernier time interval measurement using triggered phase-locked oscillators

Abstract: Measurement of a time interval between a start and a stop event is made by activating a start oscillator in response to the start event and activating a stop oscillator in response to the stop event. The number of cycles of each respective oscillator signal which occur between the activation of each oscillator and the coincidence of the respective oscillator signal with that of an independent time base is determined. The number of cycles of the time base signal between the coincident points of it and the start and stop oscillator signal is also determined. These numbers, which are always integers, are used along with the values for the time base period and the difference in frequency between the time base oscillator and the start and stop oscillators to calculate the time interval. Resolution of the measurement is dependent on the frequency difference between the time base signal and the start and stop oscillator signals. Two triggered-phase oscillators, which are phase-locked to the reference oscillator, are used to supply the start and stop frequencies. The start trigger and stop signals are used for phase shifting, i.e., restarting of the oscillators rather than starting the oscillators. This allows for pre-trigger frequency control, and essentially eliminates post trigger frequency drift which usually occurs when an oscillator is first started. The coincidence signals are provided by the phase cross-over between the phase locked oscillator and the reference by a digital mixer.

Method and apparatus for programmable and remote numeric control and calibration of electronic instrumentation

Abstract: The present invention provides programmable, remote and automatic numeric control and calibration of analog signal measuring and generating apparatus. Digital values for control signals for control of gain, sensitivity, frequency and the like and for calibration are stored and may be easily modified to follow complex control and calibration functions. Conventional controls are replaced by pushbuttons which initiate calculation of digital control signals for controlling the transfer function of variable elements of the apparatus. Conventional meters and dials are replaced by digital readout devices for indicating operational parameters such as amplitudes, sensitivities, frequencies and the like. Digital values for calibration factors and parameter control settings also may be recorded on suitable recording media for use under recurring conditions and environments.

Method for producing a low defect layer of silicon-on-sapphire wafer

Abstract: A method is provided for producing a low-defect layer of silicon on a sapphire substrate. A silicon-on-sapphire (SOS) wafer is formed by initially epitaxially depositing silicon on the sapphire substrate to form a monocrystalline layer which is substantially free of lattice defects near its surface, but which exhibits a high defect density near the sapphire substrate. The wafer is subsequently subjected to an ion implantation to form an amorphous region in the silicon near the silicon-sapphire interface. The implanted ions are preferably "channeled" through the silicon layer to insure that the amorphous region will be localized in the imperfect region near the substrate, leaving the upper region of the silicon layer undamaged. During a subsequent high temperature anneal cycle, monocrystalline silicon is regrown from the residual upper regions of the silicon down to the silicon-sapphire interface, producing a silicon layer having a greatly reduced defect density throughout the layer.

Optimization of nonplanar power MOS transistors

Abstract: Analysis of fundamental MOSFET parameters predicts device limits in high-voltage high-speed operation that exceed the performance of bipolar devices. The optimization of voltage, speed, and "on" resistance parameters for power MOSFET's suggests a vertical three-terminal device design with short, wide channels; a wide, lightly doped drain region; and field terminator rings at the device perimeter. Utilizing this design philosophy, VMOS transistors have been produced with source-drain breakdown voltage greater than 450 V, and 5.5-Ω "on" resistance for 2.0-mm2active area. With a high channel width packing density design and 2.5-mm2active area, a 30-V transistor has also been produced having only 0.060-Ω "on" resistance. The breakdown voltage and "on" resistance of these devices exceed the performance of other power MOSFET's currently available. Also, the switching speed of these devices (better than 15 ns) far exceeds the performance of high-voltage bipolar transistors. Measurements of drain leakage current at 200-V drain potential show a resistance ratio R_{off}/R_{on} of approximately 1010for a 20-V variation in gate-to-source voltage.

Electrode assembly for sensing heart activity

Abstract: An electrode assembly for sensing heart activity from body tissue includes a flexible guide tube, a spiral retaining coil disposed in one end of the guide tube, a handle disposed at the other end of the guide tube, and twisted wires inside the tube interconnecting the retaining coil and the handle. Rotation of the handle rotates the twisted wires, which in turn rotate the retaining coil to screw it into body tissue. A safety stop releasably disposed on the guide tube limits the rotation of the retaining coil and thus limits its depth of penetration into the body tissue. After the handle is rotated a preselected amount, the handle is automatically disengaged from the twisted wires.

Optical shaft angle encoder

Abstract: An optical comparator has three bifurcated and truncated lenses, each lens having two siamesed and truncated elements having closely spaced optical axes. This results in an optical encoder having a low sensitivity to eccentricity errors.

Fiducial point location

Abstract: Ventricular ectopic heartbeats are detected by comparing the ECG wave for a current heartbeat with the ECG wave of a heartbeat considered to be normal for that patient. The waves are aligned with their fiducial points in time coincidence, and the fiducial points are located at the centroids of the ECG waves.

Pulse generating apparatus

Abstract: A three-channel optical shaft angle encoder has two channels for encoding the incremental angle and the direction of rotation of a shaft. A third channel provides a synchronizing index pulse for encoding the absolute position of the shaft once per revolution. The encoder has an emitter module containing three high irradiance LED emitters and integral truncated collimating lenses for producing three closely spaced collimated light beams, one beam for each channel. These light beams are modulated as a function of the relative angle between a code wheel coupled to the shaft and a phase plate fixedly mounted to the body of the encoder. The modulated light beams are received by a detector module having beam splitting truncated and siamesed lenses positioned to split each of the closely spaced light beams and to focus each of the split beams onto a photo detector pair. The photo diode pairs are coupled to balanced hysteretic optical comparators which provide analog and digital output in response to the position and direction of rotation of the shaft.

Biped stability considerations with vestibular models

Abstract: Recent experimental work has resulted in certain models for the semicircular canals and otoliths. The accuracy and adequacy of these models are analyzed here by incorporating them in stability studies of biped robots-one-degree and two-degree-of-freedom inverted pendulums. It is shown that a variety of feedback signals can stabilize biped models of these types. Additional information could limit the choice of such signals.

Determination of Nematic Liquid Crystal Elastic and Dielectric Properties from the Shape of a Capacitance-Voltage Curve

Abstract: This paper shows how capacitance-voltage curves can be used to determine nematic liquid crystal dielectric and elastic constants and surface tilt angles Careful analysis of the C-V curves reveals that distortion free energy theory is useful up to a V/Vc of about two A detailed curve of tilt angle as a function of SiO deposition angle is also presented along with temperature variation in liquid crystal properties Pentylcyanobiphenyl (5CB) was used throughout the study

Photosensing Arrays with Improved Spatial Resolution

Abstract: The spatial resolution obtainable in a photosensing array used for optical imaging may be limited by the diffusion of photogenerated carriers within a uniformly doped semiconductor even if other components of the optical system are optimized and scattered light is reduced. A technique has been developed to improve the spatial resolution for critical applications by incorporating subsurface electric fields that accelerate the photogenerated carriers toward or away from the surface so that the carriers are prevented from diffusing to distant photosensing elements. The subsurface fields are obtained by incorporating suitable dopant concentration gradients into the structure. In one structure fabricated the subsurface field was formed by using a heavily doped buried layer and a lightly doped epitaxial film over a lightly doped substrate, all of the same conductivity type. This structure is compatible with the incorporation of other semiconductor devices in the same monolithic substrate. The technique has been applied to an array of photodiodes in a silicon integrated circuit, but the principle is directly applicable to other types of photosensing arrays, such as charge-coupled devices (CCD's), and other semiconductor materials.

Apparatus for spectrum analysis of an electrical signal

Abstract: An input signal is mixed with sampling signals from oscillators which vary the frequency of the sampling signal from a first frequency to a second frequency. The resulting Intermediate Frequency (IF) signal is processed and digital values are stored in a memory in response thereto. Waveforms are then displayed which correspond to these frequency and amplitude values. Various input and display circuits facilitate the display and interpretation of these waveforms.

Coupling circuit with driven guard

Abstract: In signal measurement circuits which are referred to a floating ground and which derive their input signals from electrodes attached to a patient's body, the effects of common mode potentials on the patient's body are minimized without requiring any patient electrodes other than those acting as signal sources by using a unity gain amplifier to drive the floating ground toward the common mode potential on the patient's body. This process is accomplished without significantly degrading the isolation impedance between the measurement circuits and true ground. The patient is protected from hazardous electrical shock by referencing the unity gain amplifier to a given point and connecting a large impedance between that point and true ground.

Low-noise microwave bipolar transistor with sub-half-micrometer emitter width

Abstract: This paper presents details of the fabrication process and performance of an n-p-n silicon microwave bipolar transistor with emitter opening widths as small as 0.3 µm. The fabrication process involves local oxidation, ion implantation, and lateral etching techniques for emitter definition. Noise figure as low as 1.0 dB at 1.5 GHz, 2.0 dB at 4 GHz, and 3.3 d B at 6 GHz were achieved. Measured noise figures and S -parameters are shown to be in approximate agreement with modeled performance based on device structure and process parameters. Prospects for further reductions in bipolar transistor noise figures are discussed.

A monolithic integrated 4-GHz amplifier

Abstract: Monolithic GaAs MESFET integrated voltage amplifier stages with 7dB gain from dc to 4GHz, and 12dB gain from dc to 2.5GHz will be reported. A three-stage amplifier with variable frequency peaking shows a maximum of 28dB gain at 2GHz.

Spectrum analyzer having enterable offsets and automatic display zoom

Abstract: An input signal is mixed with sampling signals from oscillators which vary the frequency of the sampling signal from a first frequency to a second frequency. The resulting Intermediate Frequency (IF) signal is processed and digital values are stored in a memory in response thereto. Waveforms are then displayed which correspond to these frequency and amplitude values. Various input and display circuits facilitate the display and interpretation of these waveforms.

Permanent magnetic hold down for steel rule dies

Abstract: Basic steel rule dies are provided which can be combined to produce a variety of die cut patterns. Each basic die contains sufficient magnetic material to hold it in place on a steel chase during the cutting operation.

Oscillator having a quartz resonator cut to compensate for static and dynamic thermal transients

Abstract: A method and apparatus utilizing a quartz crystal resonator with an orientation substantially equal to (yxwl) 21.93°/33.93° vibrating simultaneously in two thickness modes to provide a stable frequency signal source. By combining a quartz crystal resonator of the above type with either digital or analog compensation, the frequency-temperature deviation of one of the crystal mode frequencies is used as an internal thermometer and the second crystal mode frequency as a reference frequency signal. The frequency signal for the thermometer function is utilized by the compensation network to stabilize the frequency of the reference signal. Additionally, the analog or digital compensation is accomplished by means of either a curve-fitting routine or an interpolation look-up table routine.

Optical fiber coating

Abstract: An optical fiber is coated with an inorganic non-metallic coating to form a thin seal. The coating is preferably applied on-line by a process such as chemical vapor deposition.

Coupling circuit with driven guard

Abstract: In signal measurement circuits which are referred to a floating ground and which derive their input signals from electrodes attached to a patient's body, the effects of common mode potentials on the patient's body are minimized without requiring any patient electrodes other than those acting as signal sources, by using an operational amplifier to drive the floating ground toward the common mode potential on the patient's body. This process is accomplished without significantly degrading the isolation impedance between the measurement circuits and true ground. The patient is protected from hazardous electrical shock by incorporating a current limiting impedance in the amplifier circuit.

Photosensing arrays with improved spatial resolution

Abstract: The spatial resolution obtainable in a photosensing array used for optical imaging may be limited by the diffusion of photogenerated carriers within a uniformly doped semiconductor even if other components of the optical system are optimized and scattered light is reduced. A technique has been developed to improve the spatial resolution for critical applications by incorporating subsurface electric fields that accelerate the photogenerated carriers toward or away from the surface so that the carriers are prevented from diffusing to distant photosensing elements. The subsurface fields are obtained by incorporating suitable dopant concentration gradients into the structure. In one structure fabricated the subsurface field was formed by using a heavily doped buried layer and a lightly doped epitaxial film over a lightly doped substrate, all of the same conductivity type. This structure is compatible with the incorporation of other semiconductor devices in the same monolithic substrate. The technique has been applied to an array of photodiodes in a silicon integrated circuit, but the principle is directly applicable to other types of photosensing arrays, such as charge-coupled devices (CCD's), and other semiconductor materials.