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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Design of a Low-Light-Level Image Sensor with On-Chip Sigma-Delta Analog-to- Digital Conversion

The design and projected performance of a low-light-level active-pixel-sensor (APS) chip with semi-parallel analog-to-digital (A/D) conversion is presented. The individual elements have been fabricated and tested using MOSIS* 2 micrometer CMOS technology, although the integrated system has not yet been fabricated. The imager consists of a 128 x 128 array of active pixels at a 50 micrometer pitch. Each column of pixels shares a 10-bit A/D converter based on first-order oversampled sigma-delta (Sigma-Delta) modulation. The 10-bit outputs of each converter are multiplexed and read out through a single set of outputs. A semi-parallel architecture is chosen to achieve 30 frames/second operation even at low light levels. The sensor is designed for less than 12 e^- rms noise performance.

Mendis, Sunetra K.↗
NASA NTRS2004

Taking evolutionary circuit design from experimentation to implementation: some useful techniques and a silicon demonstration

Current techniques in evolutionary synthesis of analogue and digital circuits designed at transistor level have focused on achieving the desired functional response, without paying sufficient attention to issues needed for a practical implementation of the resulting solution. No silicon fabrication of circuits with topologies designed by evolution has been done before, leaving open questions on the feasibility of the evolutionary circuit design approach, as well as on how high-performance, robust, or portable such designs could be when implemented in hardware. It is argued that moving from evolutionary 'design-for experimentation' to 'design-for-implementation' requires, beyond inclusion in the fitness function of measures indicative of circuit evaluation factors such as power consumption and robustness to temperature variations, the addition of certain evaluation techniques that are not common in conventional design. Several such techniques that were found to be useful in evolving designs for implementation are presented; some are general, and some are particular to the problem domain of transistor-level logic design, used here as a target application. The example used here is a multifunction NAND/NOR logic gate circuit, for which evolution obtained a creative circuit topology more compact than what has been achieved by multiplexing a NAND and a NOR gate. The circuit was fabricated in a 0.5 mum CMOS technology and silicon tests showed good correspondence with the simulations.

digital circuits designs↗
NASA NTRS2006

Protocol Sensing Across Multiple Space Missions

In this work, we present sensing performance using an architecture for a reconfigurable protocol chip for spacebased applications. Toward utilizing the IP packet architecture, utilizing data link layer framing structures for multiplexed data on a channel are the targeted application considered for demonstration purposes. Specifically, we examine three common framing standards and present the sensing performance of these standards and their relative de-correlation metrics. Some analysis is performed to investigate the impact of lossy links and on the number of packets required to perform a decision with some probability. Finally, we present results on a demonstration platform that integrated reconfigurable sensing technology into the Ground Station Interface Device (GRID) for End-to-End IP demonstrations in space.

Ground Station Interface Device (GRID)↗
NASA NTRS2006

Reconfigurable Protocol Sensing in an End-to-End Demonstration

In this work, we present sensing performance using an architecture for a reconfigurable protocol chip for spacebased applications. Toward utilizing the IP packet architecture, utilizing data link layer framing structures for multiplexed data on a channel are the targeted application considered for demonstration purposes. Specifically, we examine three common framing standards and present the sensing performance of these standards and their relative de-correlation metrics. Some analysis is performed to investigate the impact of lossy links. Finally, we present results on a demonstration platform that integrated reconfigurable sensing technology into the Ground Station Interface Device (GRID) for End-to-End IP demonstrations in space.

space based applications↗
NASA NTRS2007

GISMO

The 2 mm (1 50 GHz) atmospheric window enables unparalleled ground-based observations of the earliest active dusty galaxies in the universe. We have undertaken the development of a bolometer camera, GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), which will obtain large and sensitive sky maps at this wavelength. The instrument will be used at the IRAM 30 m telescope, where we hope to have a trial observing run in Spring of 2007. The innovative element in this camera is its 8x1 6 fully sampled planar array of multiplexed superconducting transition edge sensor bolometers. This array is based on our recently demonstrated Backshort Under Grid architecture, designed to be scaled to kilopixel arrays with high sensitivity (of around 4 * 10 (exp -17)/ W* square root of Hz at T(sub c) approximates 450mK). A compact cryogenic optical system provides a wide field of view, (almost 2'x4') enabling GISMO to be very efficient at detecting sources serendipitously in large sky surveys, while retaining diffraction-limited imaging performance. GISMO will provide significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for the instrument is to detect dust emission from high-z Ultraluminous Infrared Galaxies (ULIRGs) and quasars. The instrument provides an important portion of the spectrum of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Models of galaxy evolution predict that GISMO will serendipitously detect one galaxy in every four hours of observing blank sky, and that one quarter of these galaxies will be at a redshift of z > 6.5.

Benford, Dominic↗
NASA NTRS2007

GISMO, a 2 mm Bolometer Camera Optimized for the Study of High Redshift Galaxies

The 2mm spectral range provides a unique terrestrial window enabling ground based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We present a progress report for our bolometer camera GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), which will obtain large and sensitive sky maps at this wavelength. The instrument will be used at the IRAM 30 m telescope and we expect to install it at the telescope in 2007. The camera uses an 8 x 16 planar array of multiplexed TES bolometers, which incorporates our recently designed Backshort Under Grid (BUG) architecture. GISMO will be very efficient at detecting sources serendipitously in large sky surveys. With the background limited performance of the detectors, the camera provides significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for the instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high-zeta ULI RGs and quasar s, even in the summer season. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Our source count models predict that GISMO will serendipitously detect one galaxy every four hours on the blank sky, and that one quarter of these galaxies will be at a redshift of zeta 6.5.

Staguhn, J.↗
NASA NTRS2005

A New Large-Well 1024x1024 Si:As Detector for the Mid-Infrared

We present a description of a new 1024x1024 Si:As array designed for ground-based use from 5 - 28 microns. With a maximum well depth of 5e6 electrons, this device brings large-format array technology to bear on ground-based mid-infrared programs, allowing entry to the mega-pixel realm previously only accessible to the near-IR. The multiplexer design features switchable gain, a 256x256 windowing mode for extremely bright sources, and it is two-edge buttable. The device is currently in its final design phase at DRS in Cypress, CA. We anticipate completion of the foundry run in October 2005. This new array will enable wide field, high angular resolution ground-based follow up of targets found by space-based missions such as the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE).

astronomy↗
NASA NTRS1994

Conductance measurement circuit with wide dynamic range

A conductance measurement circuit to measure conductance of a solution under test with an output voltage proportional to conductance over a 5-decade range, i.e., 0.01 uS to 1000 uS or from 0.1 uS to 10,000 uS. An increase in conductance indicates growth, or multiplication, of the bacteria in the test solution. Two circuits are used each for an alternate half-cycle time periods of an alternate squarewave in order to cause alternate and opposite currents to be applied to the test solution. The output of one of the two circuits may be scaled for a different range optimum switching frequency dependent upon the solution conductance and to enable uninterrupted measurement over the complete 5-decade range. This circuitry provides two overlapping ranges of conductance which can be read simultaneously without discontinuity thereby eliminating range switching within the basic circuitry. A VCO is used to automatically change the operating frequency according to the particular value of the conductance being measured, and comparators indicate which range is valid and also facilitate computer-controlled data acquisition. A multiplexer may be used to monitor any number of solutions under test continuously.

Mount, Bruce E.↗
NASA NTRS1980

Digital optical recorder-reproducer system

A mass archival optical recording and reproduction system includes a recording light source such as a laser beam focussed and directed upon an acousto-optic linear modulator array (or page composer) that receives parallel blocks of data converted from a serial stream of digital data to be stored. The page composer imparts to the laser beam modulation representative of a plurality of parallel channels of data and through focussing optics downstream of the page composer parallel arrays of optical spots are recorded upon a suitable recording medium such as a photographic film floppy disc. The recording medium may be substantially frictionlessly and stably positioned for recording at a record/read station by an air-bearing platen arrangement which is preferably thermodynamically non-throttling so that the recording film may be positioned in the path of the information-carrying light beam in a static or dynamic mode. During readout, the page composer is bypassed and a readout light beam is focussed directly upon the recording medium containing an array of previously recorded digital spots, a sync bit, data positioning bits, and a tracking band. The readout beam which has been directed through the recording medium is then imaged upon a photodetector array, the output of which may be coupled to suitable electronic processing circuitry, such as a digital multiplexer, whereby the parallel spot array is converted back into the original serial data stream.

Reddersen, Brad R.↗
NASA NTRS1993

Differential temperature stress measurement employing array sensor with local offset

The instrument has a focal plane array of infrared sensors of the integrating type such as a multiplexed device in which a charge is built up on a capacitor which is proportional to the total number of photons which that sensor is exposed to between read-out cycles. The infrared sensors of the array are manufactured as part of an overall array which is part of a micro-electronic device. The sensor achieves greater sensitivity by applying a local offset to the output of each sensor before it is converted into a digital word. The offset which is applied to each sensor will typically be the sensor's average value so that the digital signal which is periodically read from each sensor of the array corresponds to the portion of the signal which is varying in time. With proper synchronization between the cyclical loading of the test object and the frame rate of the infrared array the output of the A/D converted signal will correspond to the stress field induced temperature variations. A digital lock-in operation may be performed on the output of each sensor in the array. This results in a test instrument which can rapidly form a precise image of the thermoelastic stresses in an object.

Lesniak, Jon R.↗
NASA NTRS1992

Fault detection and bypass in a sequence information signal processor

The invention comprises a plurality of scan registers, each such register respectively associated with a processor element; an on-chip comparator, encoder and fault bypass register. Each scan register generates a unitary signal the logic state of which depends on the correctness of the input from the previous processor in the systolic array. These unitary signals are input to a common comparator which generates an output indicating whether or not an error has occurred. These unitary signals are also input to an encoder which identifies the location of any fault detected so that an appropriate multiplexer can be switched to bypass the faulty processor element. Input scan data can be readily programmed to fully exercise all of the processor elements so that no fault can remain undetected.

Peterson, John C.↗
NASA NTRS1992

Method for scrambling satellite communications

A secure communications system multiplexes segments of the information signal for keyed encoding and modulation onto a plurality of different carrier frequencies and/or polarizations, and transmits the encoded carriers to multi-channel signal summing receivers that decode the segments from all channels, to reassemble the information signal for use by authorized stations with a key. The use of the multi-channel link and the summing receiver allows the greatest number of different coding algorithms for accommodating the greatest number of discrete secure channels.

Brockman, Milton H.↗
NASA NTRS1998

Bright field illumination system

A Bright Field Illumination system for inspecting a range of characteristically different kinds of defects, depressions, and ridges in a selected material surface. The system has an illumination source placed near a first focus of an elliptical reflector. In addition, a camera facing the inspected area is placed near the illumination source and the first focus. The second focus of the elliptical reflector is located at a distance approximately twice the elliptical reflector's distance above the inspected surface. The elliptical reflector directs the light from the source onto the inspected surface. Due to the shape of the elliptical reflector, light that is specularly reflected from the inspected surface is directed into the camera is which located at the position of the reflected second focus of the ellipse. This system creates a brightly lighted background field against which damage sites appear as high contrast dark objects which can be easily detected by a person or an automated inspection system. In addition, the Bright Field Illumination system and method can be used in combination with a vision inspection system providing for multiplexed illumination and data handling of multiple kinds of surface characteristics including abrupt and gradual surface variations and differences between measured characteristics of different kinds and prior instruments.

Huber, Edward D.↗
NASA NTRS2001

Bit-serial neuroprocessor architecture

A neuroprocessor architecture employs a combination of bit-serial and serial-parallel techniques for implementing the neurons of the neuroprocessor. The neuroprocessor architecture includes a neural module containing a pool of neurons, a global controller, a sigmoid activation ROM look-up-table, a plurality of neuron state registers, and a synaptic weight RAM. The neuroprocessor reduces the number of neurons required to perform the task by time multiplexing groups of neurons from a fixed pool of neurons to achieve the successive hidden layers of a recurrent network topology.

Tawel, Raoul↗
NASA NTRS2002

Focal plane infrared readout circuit

An infrared imager, such as a spectrometer, includes multiple infrared photodetectors and readout circuits for reading out signals from the photodetectors. Each readout circuit includes a buffered direct injection input circuit including a differential amplifier with active feedback provided through an injection transistor. The differential amplifier includes a pair of input transistors, a pair of cascode transistors and a current mirror load. Photocurrent from a photodetector can be injected onto an integration capacitor in the readout circuit with high injection efficiency at high speed. A high speed, low noise, wide dynamic range linear infrared multiplexer array for reading out infrared detectors with large capacitances can be achieved even when short exposure times are used. The effect of image lag can be reduced.

Pain, Bedabrata↗
NASA NTRS2002

High speed demodulation systems for fiber optic grating sensors

Fiber optic grating sensor demodulation systems are described that offer high speed and multiplexing options for both single and multiple parameter fiber optic grating sensors. To attain very high speeds for single parameter fiber grating sensors ratio techniques are used that allow a series of sensors to be placed in a single fiber while retaining high speed capability. These methods can be extended to multiparameter fiber grating sensors. Optimization of speeds can be obtained by minimizing the number of spectral peaks that must be processed and it is shown that two or three spectral peak measurements may in specific multiparameter applications offer comparable or better performance than processing four spectral peaks. Combining the ratio methods with minimization of peak measurements allows very high speed measurement of such important environmental effects as transverse strain and pressure.

Udd, Eric↗
NASA NTRS1989

Architecture for time or transform domain decoding of reed-solomon codes

Two pipeline (255,233) RS decoders, one a time domain decoder and the other a transform domain decoder, use the same first part to develop an errata locator polynomial .tau.(x), and an errata evaluator polynominal A(x). Both the time domain decoder and transform domain decoder have a modified GCD that uses an input multiplexer and an output demultiplexer to reduce the number of GCD cells required. The time domain decoder uses a Chien search and polynomial evaluator on the GCD outputs .tau.(x) and A(x), for the final decoding steps, while the transform domain decoder uses a transform error pattern algorithm operating on .tau.(x) and the initial syndrome computation S(x), followed by an inverse transform algorithm in sequence for the final decoding steps prior to adding the received RS coded message to produce a decoded output message.

Shao, Howard M.↗