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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Antenna beamforming using optical processing

This work concerns itself with the analytical investigation into the feasibility of optical processor based beamforming for microwave array antennas. The primary focus is on systems utilizing the 20 and 30 GHz communications band and a transmit configuration exclusively to serve this band. A mathematical model is developed for computation of candidate design configurations. The model is capable of determination of the necessary design parameters required for both spatial aspects of the microwave footprint (beam) formation as well as transmitted signal quality. Computed example beams transmitted from geosynchronous orbit are presented to demonstrate network capabilities. A comprehensive device/component survey is also conducted in parallel to determine the feasibility of breadboarding a transmit processor. Recommendations are made for the configuration of such a processor and the components which would comprise such a network.

Anderson, L. P., Jr.↗
NASA NTRS1991

Phased array antenna beamforming using optical processor

The feasibility of optical processor based beamforming for microwave array antennas is investigated. The primary focus is on systems utilizing the 20/30 GHz communications band and a transmit configuration exclusively to serve this band. A mathematical model is developed for computation of candidate design configurations. The model is capable of determination of the necessary design parameters required for spatial aspects of the microwave 'footprint' (beam) formation. Computed example beams transmitted from geosynchronous orbit are presented to demonstrate network capabilities. The effect of the processor on the output microwave signal to noise quality at the antenna interface is also considered.

Anderson, L. P.↗
NASA NTRS1988

Strawman Optical Reception Development Antenna (SORDA)

A strawman design of a ground-based station for receiving optical communications from deep space is presented. This strawman will serve as a basis for further study and design refinement. The recommendation to build rather than to use an existing facility is explained. Parameters of the design were selected to postulate a workable system, starting with a 10 m diameter, hexagonally segmented, f/0.5 primary mirror. The effects of variations of design parameters on performance and cost are discussed. Some design formulas are included. An electro-optical functional block diagram is presented and discussed. Cost calculations are based on a previous cost model for the hardware or on typical construction costs per unit area for several types of facilities. Other cost factors are included in the usual way for Construction of Facilities. The ratio of high and low reasonable values was less than a factor of 2, with a best estimate of under $16,000,000.

Kerr, E. L.↗
NASA NTRS2012

Detection Performance of Upgraded "Polished Panel" Optical Receiver Concept on the Deep-Space Network's 34 Meter Research Antenna

Initial optical communications experiments with a Vertex polished aluminum panel have been described. The polished panel was mounted on the main reflector of the DSN's research antenna at DSS-13. The PSF was recorded via remotely controlled digital camera mounted on the subreflector structure. Initial PSF generated by Jupiter showed significant tilt error and some mechanical deformation. After upgrades, the PSF improved significantly, leading to much better concentration of light. Communications performance of the initial and upgraded panel structure were compared. After the upgrades, simulated PPM symbol error probability decreased by six orders of magnitude. Work is continuing to demonstrate closed-loop tracking of sources from zenith to horizon, and better characterize communications performance in realistic daytime background environments.

polished panel optical receiver↗
NASA NTRS1997

Feasibility Study of Optically Transparent Microstrip Patch Antenna

The paper presents a feasibility study on optically transparent patch antennas with microstrip line and probe feeds. The two antennas operate at 2.3 GHz and 19.5 GHz respectively. They are constructed from a thin sheet of clear polyester with an AgHT-8 optically transparent conductive coating. The experimental results show good radiation patterns and input impedance match. The antennas have potential applications in mobile wireless communications.

Simons, Rainee N.↗
NASA NTRS1997

Feasibility Study of Optically Transparent Microstrip Patch Antenna

The paper presents a feasibility study on optically transparent patch antennas with microstrip line and probe feeds. The two antennas operate at 2.3 GHz and 19.5 GHz respectively. They are constructed from a thin sheet of clear polyester with an AgHT-8 optically transparent conductive coating. The experimental results show good radiation patterns and input impedance match. The antennas have potential applications in mobile wireless communications.

Simons, Rainee N.↗
NASA NTRS2007

Optical Phased Array Antennas using Coupled Vertical Cavity Surface Emitting Lasers

High data rate communication links are needed to meet the needs of NASA as well as other organizations to develop space-based optical communication systems. These systems must be robust to high radiation environments, reliable, and operate over a wide temperature range. Highly desirable features include beam steering capability, reconfigurability, low power consumption, and small aperture size. Optical communication links, using coupled vertical cavity surface emitting laser radiating elements are promising candidates for the transmit portion of these communication links. In this talk we describe a mission scenario, and how the antenna requirements are derived from the mission needs. We describe a potential architecture for this type of antenna, and outline the advantages and drawbacks of this approach relative to competing technologies. The technology we are proposing used coupled arrays of 1550 nm vertical cavity surface emitting lasers for transmission. The feasibility of coupling these arrays together, to form coherent high-power beams that can be modulated at data rates exceeding 1 Gbps, will be explored. We will propose an architecture that enables electronic beam steering, thus mitigating the need for ancillary acquisition, tracking and beam pointing equipment such as needed for current optical communicatin systems. The beam-steering capability we are proposing also opens the possibility of using this technology for inter-satellite communicatin links, and satellite-to-surface links.

Mueller, Carl H.↗
NASA NTRS1994

Research and development optical deep space antenna sizing study

Results from this study provide a basis for the selection of an aperture size appropriate for a research and development ground-based receiver for deep space optical communications. Currently achievable or near-term realizable hardware performance capabilities for both a spacecraft optical terminal and a ground terminal were used as input parameters to the analysis. Links were analyzed using OPTI, our optical link analysis program. Near-term planned and current missions were surveyed and categorized by data rate and telecommunications-subsystems prime power consumption. The spacecraft optical-terminal transmitter power was selected by matching these (RF) data rates and prime power requirements and by applying power efficiencies suitable to an optical communications subsystem. The study was baselined on a Mars mission. Results are displayed as required ground aperture size for given spacecraft transmitter aperture size, parametrized by data rate, transmit optical power, and wavelength.

Wonica, D.↗
NASA NTRS2007

Optically Transparent Split-Ring Antennas for 1 to 10 GHz

Split-ring antennas made from optically transparent, electrically conductive films have been invented for applications in which there are requirements for compact antennas capable of operation over much or all of the frequency band from 1 to 10 GHz. Primary examples of such applications include wireless local-area networks and industrial, scientific, and medical (ISM) applications. These antennas can be conveniently located on such surfaces as those of automobile windows and display screens of diverse hand-held electronic units. They are fabricated by conventional printed-circuit techniques and can easily be integrated with solid-state amplifier circuits to enhance gain. The structure of an antenna of this type includes an antenna/feed layer supported on the top or outer face of a dielectric (e.g., glass) and, optionally, a ground layer on the bottom or inner face of the substrate. The ring can be in the form of either a conductive strip or a slot in the antenna/feed layer. The ring can be of rectangular, square, circular, elliptical, or other suitable shape and can be excited by means of a microstrip, slot line, or coplanar waveguide. For example, the antenna shown in the figure features a square conductive-strip split ring with a microstrip feed. In general, an antenna fed at its external boundary in the manner of this invention presents very high impedance, thereby creating an impedance-matching problem. Splitting the ring . that is, cutting a notch through the ring . offers a solution to the problem in that the notch fixes the location of maximum electric field, which location is directly related to the impedance. Thus, an excellent impedance match can be achieved through proper choice of the location of the notch. In geometric layout, such a ring antenna structure is typically between 1.4 and 1.3 the size of a patch antenna capable of operating in the same frequency range. This miniaturization of the antenna is desirable, not only because it contributes to overall miniaturization of equipment, but also because minimization of the extent of the optically transparent, electrically conductive film helps to minimize the electrical loss associated with the surface resistance ( 5 ohms per square) of the transparent, electrically conductive film material. Incidentally, even at 5 ohms per square, this surface resistance is significantly less than that of indium tin oxide film (typically > 25 ohms per square), which, heretofore has been the transparent, electrically conductive film material of choice. At the time of writing this article, information on the composition of the lower-resistance film used in the antennas of this invention was not available.

Lee, Richard Q.↗
NASA NTRS1987

Analysis of a Four-Reflector S/X-Band Antenna

Physical optics accounts for near field, cross polarization, and higher-order modes. Report presents physical-optics analysis of four-reflector, 64-m antennas of Deep Space Network. Analysis thorough and detailed. Report has instructional value as example for designers of large microwave dishes with subreflectors and involving reflector surfaces with hyperboloidal, paraboloidal, ellipsoidal, and more complex shapes.

Cha, Alan G.↗
NASA NTRS1994

Impact of Optical Baffle on Antenna Pattern

One of the major concerns of antenna design for spacecraft applications is the effect of surrounding structures which can reflect and diffract the antenna's radiated energy and cause degradation in the antenna directivity, beam shape, and sidelobe levels.

Earth Observing System (EOS)↗
NASA NTRS1986

Deformable Subreflector Computed by Geometric Optics

Distorted antenna surfaces forced to produce a uniform wave front. SUBFORMING employs geometric optics in determining subreflector coordinates to match main reflector surface with known distortions. Antenna with distorted paraboloidal reflecting surface forced to produce uniform wave front by using a Cassegrainian geometry with path-length-compensating subreflector. Program written in FORTRAN V for batch execution.

Williams, W. F.↗
NASA NTRS1979

Surface accuracy measurement system deployable reflector antennas

Conceptual optical sensor configurations for measuring the surface deformations of large, deployable space antennas are described. These antennas include precision deployable reflectors up to 30 meters diameter and 1000 GHz frequency and mesh deployable reflectors up to 100 meters diameter and 30 GHz frequency. For each representative antenna configuration, the surface deformation sensor provides continuous, real-time measurements at a sufficient number of sample points to be compatible with active surface control. Moreover, the sensor system does not interfere with the mechanical or microwave characteristics of either the antenna surface or the feed. For the applications considered, the sensor system consists of a central receiver ring containing six to ten long focal length, angle measuring instruments, each viewing a dedicated set of bright point targets at the antenna. The targets, either light emitting diodes or illuminated retroreflectors, are modulated to eliminate errors from spurious backgrounds. Very preliminary performance estimates indicate that the sensor system, using commerical grade components, can produce a 20th to a 30th wavelength accuracy (3 sigma).

Neiswander, R. S.↗
NASA NTRS2011

Polished Panel Optical Receiver for Simultaneous RF/Optical Telemetry with Large DSN Antennas

The polished panel optical receiver concept described here makes use of aluminum panels on the main reflector of the Deep Space Network's (DSN's) 34-meter antennas at optical wavelengths by polishing and coating their surface to efficiently reflect near-infrared wavelengths in the 1,064 1,550-nanometer range. Achievable surface smoothness is not a limiting factor for aluminum panels, and initial field experiments indicate that the surface quality of microwave aluminum panels is sufficient to concentrate the light into small, but not diffraction-limited, spots at their primary focus. Preliminary analysis of data from high-quality microwave panels has shown that the light can be concentrated into 200 400 microradian cones, resulting in spot diameters of 2-4 mm at the 10-meter primary focus F(0) shown in the figure, or 2-4 cm spots at F(1) after magnification by the subreflector, which results in an effective focal length of about 100 meters. Three distinct implementation options are possible, with theoretically identical tracking and communications performance: Option 1: The communications assembly could be placed directly behind the subreflector at F(0), but this placement would require replacing the existing all-aluminum subreflector with a new design that transmits optical wavelengths but reflects RF, thus transmitting the optical signal to the primary focus of the parabolic polished aluminum panels at F(0), as shown in the figure. Option 2: Alternately, the optical communications assembly could be located near the first available focal-spot F(1) following reflection by the subreflector (which would have to be polished), next to the input to the beam waveguide on the main reflector as shown in the figure. Option 3: Finally, the optical communications assembly could be placed inside the pedestal room, and separated from the RF signal after the ellipsoid and before the signal reached the microwave receiver via an RF/optical dichroic near F(3).

Vilnrotter, Victor A.↗
NASA NTRS1986

Optically controlled phased array antenna concepts using GaAs monolithic microwave integrated circuits

The desire for rapid beam reconfigurability and steering has led to the exploration of new techniques. Optical techniques have been suggested as potential candidates for implementing these needs. Candidates generally fall into one of two areas: those using fiber optic Beam Forming Networks (BFNs) and those using optically processed BFNs. Both techniques utilize GaAs Monolithic Microwave Integrated Circuits (MMICs) in the BFN, but the role of the MMIC for providing phase and amplitude variations is largely eliminated by some new optical processing techniques. This paper discusses these two types of optical BFN designs and provides conceptual designs of both systems.

Kunath, R. R.↗
NASA NTRS1992

Performance of a 12-GHz fiber-optic system for beam-waveguide antenna stability testing

A 12-GHz fiber-optic system is a critical part of a test configuration that was proposed for measuring the fractional frequency stability of the Deep Space Station (DSS)-13 beam-waveguide (BWG) antenna. This fiber-optic system is used to carry Ku-band (12-GHz) signals from a reference antenna to the DSS-13 BWG pedestal room. Tests performed only on the fiber-optic system portion of the overall test configuration showed that the 12-GHz fiber-optic system (installed at DSS-13) has a frequency stability of about 1.1 x 10(exp -16) for sampling time tau = 1000 sec for a nighttime run. This preliminary result establishes the lowest noise floor that can probably be achieved for the test configuration that will be used to measure the frequency stability of the DSS-13 BWG antenna.

Otoshi, T. Y.↗