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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.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

A Wideband Satcom Based Avionics Network with CDMA Uplink and TDM Downlink

The purpose of this paper is to describe some key technical ideas behind our vision of a future satcom based digital communication network for avionics applications The key features of our design are as follows: (a) Packetized transmission to permit efficient use of system resources for multimedia traffic; (b) A time division multiplexed (TDM) satellite downlink whose physical layer is designed to operate the satellite link at maximum power efficiency. We show how powerful turbo codes (invented originally for linear modulation) can be used with nonlinear constant envelope modulation, thus permitting the satellite amplifier to operate in a power efficient nonlinear regime; (c) A code division multiple access (CDMA) satellite uplink, which permits efficient access to the satellite from multiple asynchronous users. Closed loop power control is difficult for bursty packetized traffic, especially given the large round trip delay to the satellite. We show how adaptive interference suppression techniques can be used to deal with the ensuing near-far problem; (d) Joint source-channel coding techniques are required both at the physical and the data transport layer to optimize the end-to-end performance. We describe a novel approach to multiple description image encoding at the data transport layer in this paper.

Agrawal, D.↗
NASA NTRS2012

Design and Performance of a Wideband Radio Telescope

The Goldstone Apple Valley Radio Telescope (GAVRT) is an outreach project, a partnership involving NASA's Jet Propulsion Laboratory (JPL), the Lewis Center for Educational Research (LCER), and the Apple Valley Unified School District near the NASA Goldstone deep space communication complex. This educational program currently uses a 34-meter antenna, DSS12, at Goldstone for classroom radio astronomy observations via the Internet. The current program utilizes DSS12 in two narrow frequency bands around S-band (2.3 GHz) and X-band (8.45 GHz), and is used by a training program involving a large number of secondary school teachers and their classrooms. To expand the program, a joint JPL/LCER project was started in mid-2006 to retrofit an additional existing 34-meter beam-waveguide antenna, DSS28, with wideband feeds and receivers to cover the 0.5-to- 14-GHz frequency bands. The DSS28 antenna has a 34-meter diameter main reflector, a 2.54-meter subreflector, and a set of beam waveguide mirrors surrounded by a 2.43-meter tube. The antenna was designed for high power and a narrow frequency band around 7.2 GHz. The performance at the low end of the frequency band desired for the educational program would be extremely poor if the beam waveguide system was used as part of the feed system. Consequently, the 34-meter antenna was retrofitted with a tertiary offset mirror placed at the vertex of the main reflector. The tertiary mirror can be rotated to use two wideband feeds that cover the 0.5-to-14-GHz band. The earlier designs for both GAVRT and the DSN only used narrow band feeds and consequently, only covered a small part of the S- and X-band frequencies. By using both a wideband feed and wideband amplifiers, the entire band from 0.5 to 14 GHz is covered, expanding significantly the science activities that can be studied using this system.

Weinreb, Sander↗
NASA NTRS2017

Wideband Reconfigurable Harmonically Tuned GaN SSPA for Cognitive Radios

The paper presents the architecture of a wideband reconfigurable harmonically-tuned Gallium Nitrate (GaN) Solid State Power Amplifier (SSPA) for cognitive radios. When interfaced with the physical layer of a cognitive communication system, this amplifier topology offers broadband high efficiency through the use of multiple tuned input/output matching networks. This feature enables the cognitive radio to reconfigure the operating frequency without sacrificing efficiency. This paper additionally presents as a proof-of-concept the design, fabrication, and test results for a GaN inverse class-F type amplifier operating at X-band (8.4 GHz) that achieves a maximum output power of 5.14-W, Power Added Efficiency (PAE) of 38.6, and Drain Efficiency (DE) of 48.9 under continuous wave (CW) operation.

Cognitive↗
NASA NTRS2017

Multiband Reconfigurable Harmonically Tuned Gallium Nitride (GaN) Solid-State Power Amplifier (SSPA) for Cognitive Radios

The paper presents the architecture of a wideband reconfigurable harmonically-tuned Gallium Nitride (GaN) Solid State Power Amplifier (SSPA) for cognitive radios. When interfaced with the physical layer of a cognitive communication system, this amplifier topology offers broadband high efficiency through the use of multiple tuned input/output matching networks. This feature enables the cognitive radio to reconfigure the operating frequency without sacrificing efficiency. This paper additionally presents as a proof-of-concept the design, fabrication, and test results for a GaN inverse Class-F type amplifier operating at X-band (8.4 GHz) that achieves a maximum output power of 5.14-W, Power Added Efficiency (PAE) of 38.6 percent, and Drain Efficiency (DE) of 48.9 percent under continuous wave (CW) operation.

Cognitive↗
NASA NTRS1980

A new phase for NASA's communications satellite program

NASA's research in communications satellite technology is discussed, including orbit-efficient techniques and applications by the commercial sector. Attention is given to expanding the capacities of the C-band (6-4 GHz) and the Ku-band (14-11 GHz), opening the Ka-band (30/20 GHz), broadly applied 're-use' of the spectrum, and developing multibeam spacecraft antennas with on-board switching. Increasing wideband services in video, high-speed data, and voice trunking is considered, as are narrow-band systems that may be used for data collection or public safety, with possible expansion to a thin-route satellite system. In particular, communication for medical, disaster, or search-and-rescue emergencies may be met by the integration of a satellite service with land mobile communications via terrestrial radio links. Also considered is a large geostationary platform providing electrical power, thermal rejection, and orbital station-keeping for many communications payloads.

Dement, D. K.↗
NASA NTRS1975

Data handling for the modular observatory

The current paper summarizes work undertaken at TRW for the EOS satellite and related missions, and it presents conclusions that lead to a flexible and low-cost overall system implementation. It shows how the usual communication and data handling functions must be altered to meet the modularization ground rules, and it demonstrates the modularization that is possible in the handling of wideband payload data both on board and on the ground.

Taber, J. E.↗
NASA NTRS1976

Orbiter KU-band transmitter

The design, build, and test of an engineering breadboard Ku band quadraphase shift keyed and wideband frequency modulated transmitter are described. This orbiter Ku band transmitter drawer is to simulate the orbiter transmitter and meet the functional requirements of the orbiter communication link.

Halterman, R.↗
NASA NTRS1982

Provision of 9.6-kbps wideband data rate capability in the DSN

The new 9.6-kbps wideband data rate capability in the DSN is reviewed. A functional description of the completed implementation is presented, together with a plan to upgrade the central communications terminal for additional 9.6 s operational flexibility.

Brunder, G. J.↗
NASA NTRS2012

Ka-Band Waveguide Three-Way Serial Combiner for MMIC Amplifiers

In this innovation, the three-way combiner consists internally of two branch-line hybrids that are connected in series by a short length of waveguide. Each branch-line hybrid is designed to combine input signals that are in phase with an amplitude ratio of two. The combiner is constructed in an E-plane split-block arrangement and is precision machined from blocks of aluminum with standard WR-28 waveguide ports. The port impedances of the combiner are matched to that of a standard WR-28 waveguide. The component parts include the power combiner and the MMIC (monolithic microwave integrated circuit) power amplifiers (PAs). The three-way series power combiner is a six-port device. For basic operation, power that enters ports 3, 5, and 6 is combined in phase and appears at port 1. Ports 2 and 4 are isolated ports. The application of the three-way combiner for combining three PAs with unequal output powers was demonstrated. NASA requires narrow-band solid-state power amplifiers (SSPAs) at Ka-band frequencies with output power in the range of 3 to 5 W for radio or gravity science experiments. In addition, NASA also requires wideband, high-efficiency SSPAs at Ka-band frequencies with output power in the range of 5 to 15 W for high-data-rate communications from deep space to Earth. The three-way power combiner is designed to operate over the frequency band of 31.8 to 32.3 GHz, which is NASA s deep-space frequency band.

Wintucky, Edwin G.↗
NASA NTRS1989

30 GHz Commercial Satellite Receivers

NASA's research and development work in satellite communications for the past 10 years has included a major technology thrust aimed at opening the Ka frequency band to commercial exploitation. This has included the development and testing of advanced system network architectures, on-board switching and processing, multibeam and phased array antennas, and satellite and ground terminal RF and digital hardware. Development work in system hardware has focused on critical components including power amplifiers, satellite IF switch matrices, low noise receivers, baseband processors, and high data rate bandwidth efficient modems. This paper describes NASA's work in developing and testing 30 GHz low noise satellite receivers for commercial space communications uplink applications. Frequencies allotted for fixed service commercial satellite communications in the Ka band are 27.5 - 30.0 GHz for uplink transmission and 17.7 - 20.2 GHz for downlink transmission. The relatively large 2.5 GHz bandwidth lends itself to wideband, high data rate digital transmission applications.

Kerczewski, Robert J.↗
NASA NTRS2019

Haystack Ultra-Wideband Satellite Imaging Radar Measurements of the Orbital Debris Environment: 2014-2017

Since the founding of the NASA Orbital Debris Program Office (ODPO) in 1979, the knowledge that orbital debris poses a risk to operational satellites and human spaceflight has been publically available. Services that rely on satellite-based technology such as communications, internet, navigation, and weather forecasting, to name a few, are ubiquitous in modern society. The International Space Station (ISS) has been continuously inhabited by a crew of up to six astronauts since November 2000 and makes, on average, approximately one debris avoidance maneuver per year to avoid objects that are large enough to be tracked by ground-based radars. This places an increased need for understanding the current status of the debris environment (measurements), for the ability to predict the future environment (modeling), and for understanding risk factors for debris creating events (mitigation). For NASA, the measurements, modeling, and mitigation aspects of orbital debris are led by the NASA ODPO at the Johnson Space Center (JSC) in Houston, Texas.This report summarizes radar measurement data from the Haystack Ultra-wideband Satellite Imaging Radar (HUSIR) operated by the Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL) and provided to the NASA ODPO. The time period covered by this report includes data collected during the U.S. government fiscal year (FY) 2014 through FY2017. The U.S. government FY begins on 1 October and lasts through 30 September of a given year (i.e., FY2014 lasts from 1 October 1 2013 through 30 September 30 2014). At this report’s release, processed data was unavailable from the Haystack Auxiliary Radar (HAX) due to errors in the calibration data for the radar and limited transmit power; a decision was made by NASA not to collect low-power HAX radar data. This is being resolved by NASA and MIT/LL and data collected during this time period will be released in a separate report.

DRADIS↗
NASA NTRS1982

Single-mode fiber systems for deep space communication network

The present investigation is concerned with the development of single-mode optical fiber distribution systems. It is pointed out that single-mode fibers represent potentially a superior medium for the distribution of frequency and timing reference signals and wideband (400 MHz) IF signals. In this connection, single-mode fibers have the potential to improve the capability and precision of NASA's Deep Space Network (DSN). Attention is given to problems related to precise time synchronization throughout the DSN, questions regarding the selection of a transmission medium, and the function of the distribution systems, taking into account specific improvements possible by an employment of single-mode fibers.

Lutes, G.↗
NASA NTRS1979

Miniature Ku-Band down converter

Hybrid circuit serves as receiver front end for 13.75- to 14.0-GHz communications and radar systems. Complete microwave integrated circuit (MIC) assembly is packaged in small hermetically welded, nitrogen-filled aluminum case. Simplicity and size proves useful for lower-frequency wideband applications.

Norbury, D. A.↗
NASA NTRS2013

Multimode Directional Coupler for Utilization of Harmonic Frequencies from TWTAs

A novel waveguide multimode directional coupler (MDC) intended for the measurement and potential utilization of the second and higher order harmonic frequencies from high-power traveling wave tube amplifiers (TWTAs) has been successfully designed, fabricated, and tested. The design is based on the characteristic multiple propagation modes of the electrical and magnetic field components of electromagnetic waves in a rectangular waveguide. The purpose was to create a rugged, easily constructed, more efficient waveguide- based MDC for extraction and exploitation of the second harmonic signal from the RF output of high-power TWTs used for space communications. The application would be a satellitebased beacon source needed for Qband and V/W-band atmospheric propagation studies. The MDC could function as a CW narrow-band source or as a wideband source for study of atmospheric group delay effects on highdata- rate links. The MDC is fabricated from two sections of waveguide - a primary one for the fundamental frequency and a secondary waveguide for the second harmonic - that are joined together such that the second harmonic higher order modes are selectively coupled via precision- machined slots for propagation in the secondary waveguide. In the TWTA output waveguide port, both the fundamental and the second harmonic signals are present. These signals propagate in the output waveguide as the dominant and higher order modes, respectively. By including an appropriate mode selective waveguide directional coupler, such as the MDC presented here at the output of the TWTA, the power at the second harmonic can be sampled and amplified to the power level needed for atmospheric propagation studies. The important conclusions from the preliminary test results for the multimode directional coupler are: (1) the second harmonic (Ka-band) can be measured and effectively separated from the fundamental (Ku-band) with no coupling of the latter, (2) power losses in the fundamental frequency are negligible, and (3) the power level of the extracted second harmonic is sufficient for further amplification to power levels needed for practical applications. It was also demonstrated that third order and potentially higher order harmonics are measurable with this device. The design is frequency agnostic, and with the appropriate choice of waveguides, is easily scaled to higher frequency TWTs. The MDC has the same function but with a number of important advantages over the conventional diplexer.

Simmons, Rainee N.↗
NASA NTRSDate not supplied

Flat-Panel Wideband Dual-Circularly Polarized 8X8 Phased Array Antenna for SATCOM Applications

A wideband, dual-circularly polarized (CP) 8×8 phased array is designed for operation at K-/Ka-band, which exhibits wide impedance and axial ratio (AR) bandwidths that encompass both of the desired satellite communication (SATCOM) bands of 22.55–23.55 GHz and 25.5–27.5 GHz. The array has a scan range of ±50° and ±36° at 23.05 GHz and 26.5 GHz, which are the center frequencies of the two aforementioned bands. The array has been integrated with a beamforming network utilizing 5G silicon RFICs, and the measurement results will be presented during the conference.

phased array antenna↗
NASA NTRS1983

V-band integrated quadriphase modulator

A V-band integrated circuit quadriphase shift keyed modulator/exciter for space communications systems was developed. Intersatellite communications systems require direct modulation at 60 GHz to enhance signal processing capability. For most systems, particularly space applications, small and lightweight components are essential to alleviate severe system design constraints. Thus to achieve wideband, high data rate systems, direct modulation techniques at millimeter waves using solid state integrated circuit technology are an integral part of the overall technology developments.

Grote, A.↗
NASA NTRS1972

10-micrometer band communication terminals in space.

Ten-micrometer band communication systems using CO2 lasers for space to space links are discussed. Particular emphasis is on low earth orbiting earth observation satellites to geosynchronous satellites at high data rate. Four key technology areas are discussed: wideband mixers for Doppler tracking; tunable laser local oscillators; high data rate modulators; and laser transmitters.

Mcavoy, N.↗
NASA NTRS1990

An implementation of a reference symbol approach to generic modulation in fading channels

As mobile satellite communications systems evolve over the next decade, they will have to adapt to a changing tradeoff between bandwidth and power. This paper presents a flexible approach to digital modulation and coding that will accommodate both wideband and narrowband schemes. This architecture could be the basis for a family of modems, each satisfying a specific power and bandwidth constraint, yet all having a large number of common signal processing blocks. The implementation of this generic approach, with general purpose digital processors for transmission of 4.8 kilobits per sec. digitally encoded speech, is described.

Young, R. J.↗