Orthogonal detection to reduce common channel interference.
Demonstration that two DSB signals with overlapping spectra may be separated by finite linear demodulation procedure
SIGNAL DISTORTION↗
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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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Ionosphere Investigations
Review of ionospheric research studies and impact of studies on understanding radio communications and solar terrestrial relationships
Alpert, Ya. L.↗
Closed loop ranging system Patent
Closed loop radio communication ranging system to determine distance between moving airborne vehicle and fixed ground station
Bunce, R. C.↗
Investigation of line-of-sight propagation in dense atmosphere, phase 2 Final report, Jun. 1970 - Feb. 1971
Effect of microwave absorption and decimetric radio noise in Jovian atmospheres on radio communication in 1 to 10 GHz frequency band
Davenport, J. W.↗
Electromagnetic interference of power conditioners for solar electric propulsion
Electrical, multikilowatt power conditioning (PC) equipment needed on board a spacecraft utilizing solar electric propulsion creates an electromagnetic environment that is potentially deterimental to the science, navigation, and radio communication hardware. Within the scope of the solar electric propulsion system technology program, three lightweight, 2.5-kW PCs were evaluated in terms of their electromagnetic characteristics. It was found that the levels of radiated and conducted interference exceeded the levels anticipated for a solar electric propulsion mission. These noise emissions, however, were the result of deficient interference design in these models, rather than a basic inability to control interference in this type of PC.
Whittlesey, A. C.↗
Digital single-sideband modulation.
This paper considers digitized Weaver modulators for single-sideband modulation that can be used in radio communications and telemetering. A system of 12 such modulators to process 12 analog signals digitally is replaced by six multiplex modulators at the cost of additional computation at the input but with an overall reduction in computation time and a higher degree of accuracy. A unique digital filter is developed that can interpolate and output samples at multiples of the input sampling rate and exhibits a passband that occurs above the Nyquist frequency with no apparent distortion effects. A discussion of the Fortran simulation of a combined modulator-demodulator structure is included to verify the effectiveness of this scheme.
Singh, S.↗
An adaptive array for interference rejection.
An experimental adaptive array based on the feedback concept discussed by Widrow et al. (1967) is considered. The processing procedure described makes it possible to discriminate between 'desired' and 'undesired' signals by means of a reference signal. The application of this approach to the problem of interference rejection in radio communications is investigated. The reference signal in this case can only approximate the desired signal. A description is given of a number of experiments in which the desired signal is a modulated signal and the reference signal is a CW signal at the desired signal carrier frequency.
Riegler, R. L.↗
Intermediate memory devices
Several methods of transfer and processing of data whose practical implementation requires operational memory devices are described. Devices incorporating multistable elements are proposed and their main parameters are given. The possibility of using the proposed devices for storing information for transmission in space radio communications channels is examined.
Basalayev, G. V.↗
Precision frequency sources
The development of precision oscillators for time and frequency standards is discussed. The applications of the oscillators to radio communication, research projects, navigation systems, and calibration sources are reported. The status of a cesium beam stabilized oscillator is examined. Photographs of the components are provided. The performance of quartz and rubidium oscillators is compared with the performance of cesium resonators.
Mccoubrey, A. O.↗
Langley Research Center entry aerothermodynamic technology development in support of Pioneer Venus multiprobe mission studies
A program of entry aerothermodynamics has been conducted to support the Pioneer Venus multiprobe mission. Aspects of the study include radiative property data, radiative blockage effectiveness measurements, heating calculations, aerodynamic and convective heating studies, and radio communications blackout models. Some of the historical background for the investigation is reviewed, and recommendations are made concerning the use of the developed technology in probe design and the continuation of certain elements of the program.
Olstad, W. B.↗
Implementing OQASK by using MSK
Concept simplifies implementation of offset quadrature amplitude-shift-keyed signal when encoding digital information for transmission. Although originally developed for deep-space radio transmission, concept can find applications in various band-width constrained systems and in digital radio communications. Also is particularly useful in high volume data transmission as means of encoding and decoding.
Simon, M. K.↗
Improved LANDSAT to give better view of earth resources
The launch data of LANDSAT 3 is announced. The improved capability of the spacecrafts' remote sensors (the return beam vidicon and the multispectral scanner) and application of LANDSAT data to the study of energy supplies, food production, and global large-scale environmental monitoring are discussed along with the piggyback amateur radio communication satellite-OSCAR-D, the plasma Interaction Experiment, and the data collection system onboard LANDSAT 3. An assessment of the utility of LANDSAT multispectral data is given based on the research results to data from studies of LANDSAT 1 and 2 data. Areas studied include agriculture, rangelands, forestry, water resources, environmental and marine resources, environmental and marine resources, cartography, land use, demography, and geological surveys and mineral/petroleum exploration.
Source record↗
Extraterrestrial intelligence - An observational approach
The article surveys present and proposed search techniques for extraterrestrial intelligence in terms of technological requirements. It is proposed that computer systems used along with existing antennas may be utilized to search for radio signals over a broad frequency range. A general search within the electromagnetic spectrum would explore frequency, received power flux, spatial locations, and modulation. Previous SETI projects (beginning in 1960) are briefly described. An observation project is proposed in which the earth's rotational motion would scan the antenna beam along one declination circle in 24 hours. The 15 degree beam width would yield a mapping of 75% of the sky in an 8-day period if the beam were shifted 15 degrees per day. With the proposed instrument parameters, a sensitivity of about 10 to the -21 watt/sq m is achieved at a 0 degree declination and 1.5 GHz. In a second phase, a 26 m antenna would yield an HPBW of 0.8 degrees at 1 GHz and 0.03 degrees at 25 GHz. It is noted that the described technology would provide secondary benefits for radio astronomy, radio communications, and other fields.
Murray, B.↗
NASA technology for large space antennas
Technology developed by NASA in conjunction with industry for potential large, deployable space antennas with applications in communication, radio astronomy and earth observation is reviewed. Concepts for deployable antennas that have been developed to the point of detail design are summarized, including the advanced sunflower precision antenna, the radial rib antenna, the maypole (hoop/column) antenna and the parabolic erectable truss antenna. The assessment of state-of-the-art deployable antenna technology is discussed, and the approach taken by the NASA Large Space Systems Technology (LSST) Program to the development of technology for large space antenna systems is outlined. Finally, the further development of the wrap-rib antenna and the maypole (hoop/column) concept, which meet mission model requirements, to satisfy LSST size and frequency requirements is discussed.
Russell, R. A.↗
Radio propagation prediction services in Japan
Japanese prediction services for HF radio communications are outlined in relation to prediction method, performance and evaluation. The current prediction is based on the CCIR interim method with some modifications matching to a computer system. The principal service is the monthly median prediction issued regularly three months in advance for various communication circuits. A daily prediction for short distance circuits is being prepared by using real time ionospheric sounding data. An evaluation theory and practice is expected to be introduced in the future prediction service.
Maeda, R.↗
Techniques for prediction of large nonanalytic reflector antenna performance
Projected spacecraft missions for communications, radio astronomy and earth observations indicate a need for very large (on the order of 100 meters) space deployable or erectable antennas. This paper discusses a numerical method of analyzing reflector characteristics which is applicable to large reflector antennas whose surfaces are subject to mechanical and thermal distortions as well as fabrication and deployment errors. A technique of describing nonanalytic surface configurations by a finite number of known (measured) points was successfully applied in a computer model to predict the RF radiation pattern of a reflector using aperture plane integration techniques. The accuracy of the results is shown to be both a function of the number of measured points used and of their distribution.
Moskowitz, S. M.↗
Speed-dependent collision effects on radar back-scattering from the ionosphere
A computer code to accurately compute the fluctuation spectrum for linearly speed dependent collision frequencies was developed. The effect of ignoring the speed dependence on the estimates of ionospheric parameters was determined. It is shown that disagreements between the rocket and the incoherent scatter estimates could be partially resolved if the correct speed dependence of the i-n collision frequency is not ignored. This problem is also relevant to the study of ionospheric irregularities in the auroral E-region and their effects on the radio communication with satellites.
Theimer, O.↗
Real-Time Reed-Solomon Decoder
RS decoder uses dedicated hardware and data pipelining for high-speed operation. Parallel processing techniques provide equivalent of over one billion operations per second at one step in decoding. Decoder finds commercial application in data encoding/decoding, telemetry, and radio communications.
Lahmeyer, C. R.↗