Search NASA⌕ Search

SEARCH · Search NASA

Results for “bits”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A 32-bit Ultrafast Parallel Correlator using Resonant Tunneling Devices

An ultrafast 32-bit pipeline correlator has been implemented using resonant tunneling diodes (RTD) and hetero-junction bipolar transistors (HBT). The negative differential resistance (NDR) characteristics of RTD's is the basis of logic gates with the self-latching property that eliminates pipeline area and delay overheads which limit throughput in conventional technologies. The circuit topology also allows threshold logic functions such as minority/majority to be implemented in a compact manner resulting in reduction of the overall complexity and delay of arbitrary logic circuits. The parallel correlator is an essential component in code division multi-access (CDMA) transceivers used for the continuous calculation of correlation between an incoming data stream and a PN sequence. Simulation results show that a nano-pipelined correlator can provide and effective throughput of one 32-bit correlation every 100 picoseconds, using minimal hardware, with a power dissipation of 1.5 watts. RTD plus HBT based logic gates have been fabricated and the RTD plus HBT based correlator is compared with state of the art complementary metal oxide semiconductor (CMOS) implementations.

Kulkarni, Shriram↗
NASA NTRS2001

A novel bit-wise adaptable entropy coding technique

We present a novel entropy coding technique which is adaptable in that each bit to be encoded may have an associated probability esitmate which depends on previously encoded bits. The technique may have advantages over arithmetic coding. The technique can achieve arbitrarily small redundancy and admits a simple and fast decoder.

data compression entopy coding↗
NASA NTRS2007

How Many Bits? Radiometric Resolution as a Factor in Obtaining Forest Information with Remotely Sensed Measurements

This viewgraph presentation reviews the findings of a study that asks is 8 bits enough to obtain forest information via remote sensing with radiometric resolution. It was concluded that while there were differences in the varying resolution datasets, there was no clear evidence that increasing the quantization above 8 bits was a benefit for forestry monitoring.

Franks, Shannon↗
NASA NTRS2010

Efficient Bit-to-Symbol Likelihood Mappings

This innovation is an efficient algorithm designed to perform bit-to-symbol and symbol-to-bit likelihood mappings that represent a significant portion of the complexity of an error-correction code decoder for high-order constellations. Recent implementation of the algorithm in hardware has yielded an 8- percent reduction in overall area relative to the prior design.

Moision, Bruce E.↗
NASA NTRS2007

Lessons Learned in the Specification, Purchase, Validation and Final Installation Process of a Replacement PCM Bit Synchronizer

This paper intends to describe the lessons learned while specifying validating and installing a bit sync to replace the 30 year old Aydin Model 335a PCM bit sync used in the Space Shuttle Launch Control Center. The engineer had to analyze the original requirements and specifications and then create new requirements documentation that more correctly described our needs. One issue to consider was the removal of unnecessary requirements such as various data formats when only one format is used. The conversion to a system that no longer has an assortment of analog rotary switches required retraining of the operators. Finally, post-procurement corrections for undisclosed user requirements and missed design requirements required close contact with a manufacturer who was willing to accommodate the changes.

Price, Richard N.↗
NASA NTRS2016

NASA Glenn Steady-State Heat Pipe Code GLENHP: Compilation for 64- and 32-Bit Windows Platforms

A new version of the NASA Glenn Steady State Heat Pipe Code, designated "GLENHP," is introduced here. This represents an update to the disk operating system (DOS) version LERCHP reported in NASA/TM-2000-209807. The new code operates on 32- and 64-bit Windows-based platforms from within the 32-bit command prompt window. An additional evaporator boundary condition and other features are provided.

Fortran 77↗
NASA NTRS2016

Performance of the JPEG Estimated Spectrum Adaptive Postfilter (JPEG-ESAP) for Low Bit Rates

Frequency-based, pixel-adaptive filtering using the JPEG-ESAP algorithm for low bit rate JPEG formatted color images may allow for more compressed images while maintaining equivalent quality at a smaller file size or bitrate. For RGB, an image is decomposed into three color bands--red, green, and blue. The JPEG-ESAP algorithm is then applied to each band (e.g., once for red, once for green, and once for blue) and the output of each application of the algorithm is rebuilt as a single color image. The ESAP algorithm may be repeatedly applied to MPEG-2 video frames to reduce their bit rate by a factor of 2 or 3, while maintaining equivalent video quality, both perceptually, and objectively, as recorded in the computed PSNR values.

Linares, Irving↗
NASA NTRS2017

Analog Correlator Based on One Bit Digital Correlator

A two input time domain correlator may perform analog correlation. In order to achieve high throughput rates with reduced or minimal computational overhead, the input data streams may be hard limited through adaptive thresholding to yield two binary bit streams. Correlation may be achieved through the use of a Hamming distance calculation, where the distance between the two bit streams approximates the time delay that separates them. The resulting Hamming distance approximates the correlation time delay with high accuracy.

Prokop, Norman↗
NASA NTRS2016

A Micro Newton Impulse-Bit Hydrazine Thruster - Design, Test and Mission Applications

Recent and numerous failures of reaction wheels have cut short and/or limited the mission functions of several spacecraft including DAWN, Mars Odyssey, and Kepler among others. A micro Newton impulse-bit hydrazine thruster has the potential to backup or even replace reaction wheels on most missions, thereby extending mission life. This paper will discuss the development and test of a plug-and-play hydrazine thruster with 30 – 130 milliNewton thrust levels, and impulse bits < 50 microNewton-sec. In addition, this paper will address mission applications that include backup for, or even replacement of reaction wheels, delta-V thrust for CubeSats, and primary attitude control for the 20 – 50 kg class of spacecraft.

Parker, J. Morgan↗
NASA NTRS2024

COLUTA: Custom 8-Channel 15-bit 40-MSPS ADC for the ATLAS Liquid Argon Calorimeter Readout

The stringent radiation-tolerance, quantization requirements, and the need for seamless integration of the on-detector readout electronics chain require the design of a full-custom analog-to-digital converter (ADC) for the 182,468 channels in the ATLAS Liquid Argon (LAr) calorimeter at the Large Hadron Collider (LHC) at CERN, as part of the High-Luminosity LHC (HL-LHC) upgrade. Each of the 8 channels in the prototype 65 nm CMOS ADC with 15-bit resolution and >68 dB signal-to-noise-and-distortion ratio (SNDR), or equivalently >11 effective number of bits (ENOB), consists of a Multiplying-DAC (MDAC) and a successive-approximation (SAR) ADC. A digital data processing unit (DDPU) calibrates and serially transmits the quantized data. Initial lab characterization of 18 chips shows a minimum SNDR of 69.5 dB at full-scale at about 5 MHz and a maximum power consumption of 1.17 W; differential non-linearity (DNL) measurements show no missing codes. Additional validation of the ADC is ongoing before approximately 70k chips can be mass-produced for the upgrade.

Rui Xu↗
NASA NTRS1997

Experimental Verification of the Pulse Shepherding Concept in Dispersion-Shifted Single-Mode Fiber for Bit-Parallel Wavelength Links

A new way to dynamically control in-flight pulses by a co-propagating shepherd pulse in a wavelength divsion multiplexed (WDM) single-mode fiber system was proposed at the MPPOI '96 Conference. That system functionally resembles an optical fiber ribbon cable, except that all the bits pass on one fiber optic waveguide.

Pulse Shepherding Bit-Parallel Wavelength Links↗
NASA NTRS2018

Bit Error Rate Performance on Passive Alignment in Free Space Optical Links Using Large Core Fibers

A 20-meter free-space optical link (FSOL) is proposed for data transmission between external ISS payload sites and the main cabin at a target rate of 10 Gbps (gigabits per second). Motion between a payload site and the main cabin is predicted to cause up to 5 cm in lateral misalignment and 0.2 degrees of angular misalignment. Due to the harsh environment of space it is advantageous to locate the optical transceivers inside the spacecraft or in a controlled environment. With the optical components and transceivers in separate locations, a fiber optic cable will be required to carry light between the two. In our past work we found that the use of large-core fibers provide an increased misalignment tolerance for such systems and could eliminate the need for active control of the optics. In that work, it was shown that a 105 m core diameter fiber optic cable offered a viable low SWaP (size, weight, and power) solution for the ISS application; however, the effects of modal dispersion were not investigated. This paper will present bit error rate performance of the FSOL using these large-core fibers.

Free Space Optical Link↗