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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Broadband Uniplanar Microstrip to Slot-Line Transitions

New in line uniplanar microstrip-to-slotline transitions for MIC/MMIC and phased array slotline antenna applications are described. Such transactions are compact and suitable to be used in an open environment or inside a package or a multichip module. The transitions share the concept of using a balun which consists of two microstrip lines connected to a slotline through a pair of coupled microstrips. The transitions are studied theoretically using the finite difference time domain (FDTD) technique and measured experimentally using an HP8510C Network Analyzer. For a back-to-back configuration, an insertion loss of less than 1.3 dB per transition is achieved over a 40% 3-dB bandwidth with a minimum of 0.6 dB at the design frequency.

Dib, Nihad I.↗
NASA NTRS1996

Automatic Phase-Compensation Modules For Antennas

Automatic amplitude-controlling and phase-shifting modules developed in order to adaptively compensate for distortions in reflectors of microwave communication antennas. Antenna of type in question includes phased array of radiating antenna elements in focal plane of off-axis paraboloidal or similar reflector. Module lies on path of radio-frequency feed between each antenna element and radio-frequency transmitting/receiving equipment.

Terry, John D.↗
NASA NTRS2004

On the Fringe Field of Wide Angle LC Optical Phased Array

For free space laser communication, light weighted large deployable optics is a critical component for the transmitter. However, such an optical element will introduce large aberrations due to the fact that the surface figure of the large optics is susceptable to deformation in the space environment. We propose to use a high-resolution liquid crystal spatial light modulator to correct for wavefront aberrations introduced by the primary optical element, and to achieve very fine beam steering and shaping at the same time. A 2-D optical phased array (OPA) antenna based on a Liquid Crystal on Silicon (LCOS) spatial light modulator is described. This device offers a combination of low cost, high resolution, high accuracy, high diffraction efficiency at video speed. To quantitatively understand the influence factor of the different design parameters, a computer simulation of the device is given by the 2-D director simulation and the Finite Difference Time domain (FDTD) simulation. For the 1-D OPA, we define the maximum steering angle to have a grating period of 8 pixel/reset scheme; as for larger steering angles than this criterion, the diffraction efficiency drops dramatically. In this case, the diffraction efficiency of 0.86 and the Strehl ratio of 0.9 are obtained in the simulation. The performance of the device in achieving high resolution wavefront correction and beam steering is also characterized experimentally.

Wang, Xighua↗
NASA NTRS2004

Laser Beam Steering/shaping for Free Space Optical Communication

The 2-D Optical Phased Array (OPA) antenna based on a Liquid Crystal On Silicon (LCoS) device can be considered for use in free space optical communication as an active beam controlling device. Several examples of the functionality of the device include: beam steering in the horizontal and elevation direction; high resolution wavefront compensation in a large telescope; and beam shaping with the computer generated kinoform. Various issues related to the diffraction efficiency, steering range, steering accuracy as well as the magnitude of wavefront compensation are discussed.

Wang, Xinghua↗
NASA NTRS2018

Investigation into New Ground Based Communications Service Offerings in Response to SmallSat Trends

The number of NASA sponsored Small Satellite (SmallSat) missions is expected to continue to grow rapidly in the next decade and beyond. There is a growing trend towards more ambitious SmallSat missions, including formation flying (Constellation, Cluster, Trailing) SmallSats and SmallSats destined for lunar orbit and beyond. This paper will present an overview of new service offerings the NASA Near Earth Network (NEN) is currently investigating and demonstrating. It will describe the benefits that new service offerings such as Multiple Spacecraft Per Aperture (MSPA), Ground-based Phased Array (GBPA) antennas, Ground-based Aperture Arrays, and Ground-based Antenna Arraying could provide to individual or formation flying SmallSats anywhere from low-earth orbit to the Sun-Earth Lagrange point orbits. It will also present potential implementation options for future demonstrations at the NASA Goddard Space Flight Center (GSFC) Wallops Flight Facility (WFF) as well as goals and objectives of such demonstrations.

Schaire, Scott H.↗
NASA NTRS2018

The Multiple Access Testbed for Research in Innovative Communications Systems (MATRICS)

NASA is presently in the planning stages for the next generation earth relay architecture which will transition to Ka-band services in a new, potentially commercially-driven architecture, by 2040. To assess the performance of various technologies and architectures, the Multiple Access Testbed for Research in Innovative Communications Systems (The MATRICS), is being developed to offer a flexible emulation platform for system-level architecture and technology assessments of candidate next generation Ka-band relay and user terminal solutions. In this paper, we describe the architecture and setup of the MATRICS, which is presently housed in GRC’s 25-ft anechoic chamber.

next generation relay↗
NASA NTRSDate not supplied

Self-Healing RF/Microwave Communications Circuits/Systems for NASA Missions—A Review

The success of current and future NASA missions relies in great part on the performance reliability and robustness of the communication circuits and systems of said missions. Some of the manifestations of reliability and robustness are comprised by properties such as graceful degradation, which provide redundancy and potentially longer life to the mission, and the ability to perform efficiently in harsh environments destinations such as Venus and the Jovian and Saturnian moons Europa and Enceladus, respectively. While several approaches have been considered or are currently underway to develop communications circuitry capable of performing in harsh environments, they lack the flexibility to enable reconfigurability to preserve functionality under adverse or contingency scenarios. This paper discusses some examples of self-healing RF/Microwave communications circuits and systems that could provide advantageous options in support of NASA missions.

self-healing↗
NASA NTRSDate not supplied

Self-Healing RF/Microwave Communications Circuits/Systems for NASA Missions - A Review

The success of current and future NASA missions relies in great part on the performance reliability and robustness of the communication circuits and systems of said missions. Some of the manifestations of reliability and robustness are comprised by properties such as graceful degradation, which provide redundancy and potentially longer life to the mission, and the ability to perform efficiently in harsh environments destinations such as Venus and the Jovian and Saturnian moons Europa and Enceladus, respectively. While several approaches have been considered or are currently underway to develop communications circuitry capable of performing in harsh environments, they lack the flexibility to enable reconfigurability to preserve functionality under adverse or contingency scenarios. This paper discusses some examples of self-healing RF/Microwave communications circuits and systems that could provide advantageous options in support of NASA missions.

Self-healing↗
NASA NTRS1977

A review of performance characteristics of satellite antennas and some observations on future directions in satellite antenna design

A general review of the state-of-the-art and new directions in research and development of spacecraft antennas is presented. Three general classes of antennas are discussed: phased arrays, lenses (dielectric and waveguide), and reflector antennas. Presently, the antenna with most applications is the reflector with considerable research being performed to improve its scan and multiple beam characteristics. Future applications for spacecraft antennas and research goals to meet these projected needs also are discussed.

Mittra, R.↗
NASA NTRS2006

The UAVSAR phased array aperture

This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar instrument that is to be flown on an unmanned aerial vehicle.

antenna tile↗
NASA NTRS2007

Calibration Test Set for a Phase-Comparison Digital Tracker

An apparatus that generates four signals at a frequency of 7.1 GHz having precisely controlled relative phases and equal amplitudes has been designed and built. This apparatus is intended mainly for use in computer-controlled automated calibration and testing of a phase-comparison digital tracker (PCDT) that measures the relative phases of replicas of the same X-band signal received by four antenna elements in an array. (The relative direction of incidence of the signal on the array is then computed from the relative phases.) The present apparatus can also be used to generate precisely phased signals for steering a beam transmitted from a phased antenna array. The apparatus (see figure) includes a 7.1-GHz signal generator, the output of which is fed to a four-way splitter. Each of the four splitter outputs is attenuated by 10 dB and fed as input to a vector modulator, wherein DC bias voltages are used to control the in-phase (I) and quadrature (Q) signal components. The bias voltages are generated by digital-to-analog- converter circuits on a control board that receives its digital control input from a computer running a LabVIEW program. The outputs of the vector modulators are further attenuated by 10 dB, then presented at high-grade radio-frequency connectors. The attenuation reduces the effects of changing mismatch and reflections. The apparatus was calibrated in a process in which the bias voltages were first stepped through all possible IQ settings. Then in a reverse interpolation performed by use of MATLAB software, a lookup table containing 3,600 IQ settings, representing equal amplitude and phase increments of 0.1 , was created for each vector modulator. During operation of the apparatus, these lookup tables are used in calibrating the PCDT.

Boas, Amy↗
NASA NTRS1994

Radial microstrip slotline feed network for circular mobile communications array

In mobile and satellite communications there is a need for low cost and low profile antennas which have a toroidal pattern. Antennas that have been developed for mobile communications include a L-Band electronically steered stripline phased array, a Ka-Band mechanically steered elliptical reflector antenna and a Ka-Band printed dipole. In addition, a L-Band mechanically steered microstrip array, a L-Band microstrip phased array tracking antenna for mounting on a car roof and an X-Band radial line slotted waveguide antenna have been demonstrated. In the above electronically scanned printed arrays, the individual element radiates normally to the plane of the array and hence require a phase shifter to scan the beam towards the horizon. Scanning in the azimuth is by mechanical or electronic steering. An alternate approach is to mount microstrip patch radiators on the surface of a cone to achieve the required elevation angle. The array then scans in the azimuth by beam switching.

Simons, Rainee N.↗
NASA NTRS2006

Uplink Array Calibration via Far-Field Power Maximization

Uplink antenna arrays have the potential to greatly increase the Deep Space Network s high-data-rate uplink capabilities as well as useful range, and to provide additional uplink signal power during critical spacecraft emergencies. While techniques for calibrating an array of receive antennas have been addressed previously, proven concepts for uplink array calibration have yet to be demonstrated. This article describes a method of utilizing the Moon as a natural far-field reflector for calibrating a phased array of uplink antennas. Using this calibration technique, the radio frequency carriers transmitted by each antenna of the array are optimally phased to ensure that the uplink power received by the spacecraft is maximized.

Vilnrotter, V.↗