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NASA NTRSDate not supplied

Benefits of Ka-band GaN MMIC High Power Amplifiers With Wide Bandwidth and High Spectral/Power Added Efficiencies for Cognitive Radio Platforms

A cognitive radio on a future NASA near-Earth spacecraft will be capable of sensing its environment and dynamically adapting its operating parameters to provide the desired SATCOM service to the mission. A key component that can enable this type of operation is a high-power amplifier (HPA) that resides on the radio platform. In this paper, we present the RF performance characteristics of a Ka-band gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) based HPA for cognitive radio platforms. These characteristics include the output power, gain, power added efficiency (PAE), RMS error vector magnitude (EVM), spectral efficiency, 3rd-order intermodulation distortion (IMD) products, spectrum, spectral regrowth, noise figure (NF), and phase noise. The data presented indicates that the HPA meets NTIA, military, and commercial spectral mask requirements. In addition, we discuss the benefits offered by the above performance characteristics toward the design and implementation of a cognitive radio platform. Furthermore, as examples, we discuss three potential use cases that apply artificial intelligence (AI) and machine learning (ML) techniques and exploit the performance characteristics discussed above to provide a knowledge-based cognitive radio platform design for SATCOM. Thus, cognitive radios with performance flexibility can enable roaming and provide seamless interoperability autonomously in the future between NASA, commercial, and other space networks owned by U.S. government agencies.

Gallium nitride↗
NASA NTRS2023

Benefits of Ka-band GaN MMIC High Power Amplifiers With Wide Bandwidth and High Spectral/Power Added Efficiencies for Cognitive Radio Platforms

A cognitive radio on a future NASA near-Earth spacecraft will be capable of sensing its environment and dynamically adapting its operating parameters to provide the desired SATCOM service to the mission. A key component that can enable this type of operation is a high-power amplifier (HPA) that resides on the radio platform. In this report, we present the RF performance characteristics of a Ka-band gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) based HPA for cognitive radio platforms. These characteristics include the output power, gain, power added efficiency (PAE), RMS error vector magnitude (EVM), spectral efficiency, 3rdorder intermodulation distortion (IMD) products, spectrum, spectral regrowth, noise figure (NF), phase noise, and group delay. The data presented indicates that the HPA meets NTIA, military, and commercial spectral mask requirements. In addition, we discuss the benefits offered by the above performance characteristics toward the design and implementation of a cognitive radio platform. Furthermore, as examples, we discuss three potential use cases that apply artificial intelligence (AI) and machine learning (ML) techniques and exploit the performance characteristics discussed above to provide a knowledge-based cognitive radio platform design for SATCOM. Thus, cognitive radios with performance flexibility can enable roaming and provide seamless interoperability autonomously in the future between NASA, commercial, and other space networks owned by U.S. government agencies.

Gallium nitride↗
NASA NTRS2023

Structured Type III Radio Bursts Observed in Interplanetary Space

Context . The last few decades have seen numerous studies dedicated to fine structures of type III radio bursts observed in the meter–decameter wavelengths. Most of the explanations of the structured radio emission involve the propagation of electron beams through the strongly inhomogeneous plasma in the low corona. To date, only a few type III bursts with fine structures, observed at hecto-kilometric wavelengths, have been reported. Aims . We report here the existence of numerous structured type III radio bursts observed during the STEREO era by all three WAVES instruments on board STEREO A, B, and Wind. The aim of the study is to report and classify structured type III bursts, and to present the characteristics of their fine structures. The final goal is to try to understand the physical mechanism responsible for the generation of structured radio emission. Methods . In this study we used data from all available spacecraft, specifically STEREO and Wind. We employed 1D density models to obtain the speed of the source of type III radio emission, the electron beam. We also performed a spectral analysis of the fine structures in order to compare their characteristics with the metric–decametric fine structures. Results . The presented similarities of the type III fine structures in the metric to decametric and interplanetary wavelengths indicate that the physical processes responsible for the generation of structured type III radio bursts could be the same, at heights from the low corona to the interplanetary range. We show that the observed structuring and intermittent nature of the type III bursts can be explained by the variation in the level of density fluctuations, at different distances from the Sun.

Non-thermal radiation mechanisms↗
NASA NTRS1973

The luminosity function of quasars and its evolution: A comparison of optically selected quasars and quasars found in radio catalogs

The luminosity function of quasars and its evolution are discussed, based on comparison of available data on optically selected quasars and quasars found in radio catalogs. It is assumed that the red shift of quasars is cosmological and the results are expressed in the framework of the Lambda = 0, Q sub Q = 1 cosmological model. The predictions of various density evolution laws are compared with observations of an optically selected sample of quasars and quasar samples from radio catalogs. The differences between the optical luminosity functions, the red shift distributions and the radio to optical luminosity ratios of optically selected quasars and radio quasars rule out luminosity functions where there is complete absence of correlation between radio and optical luminosities. These differences also imply that Schmidt's (1970) luminosity function, where there exists a statistical correlation between radio and optical luminosities, although may be correct for high red shift objects, disagrees with observation at low red shifts. These differences can be accounted for by postulating existence of two classes (1 and 2) of objects.

Petrosian, V.↗
NASA NTRS1977

Radio-emitting electrons and cosmic ray confinement

Evidence from radio data obtained at frequencies of 10 to 8000 MHz for steepening of the observed background-radio-continuum spectra in the directions of the galactic Anticenter (A) and Halo Minimum (H) is used to deduce quantitative information on the variation of the magnetic field with distance from the galactic plane. The radio data are analyzed in the framework of the cosmic-ray diffusion model developed by Bulanov and Dogel (1975), and some inferences are drawn regarding the injection spectrum of cosmic-ray electrons as well as their propagation in the Galaxy. The results indicate that: (1) radio-spectrum steepening is centered around 200 MHz in the direction of H and around 330 MHz in the direction of A, implying a lower mean magnetic field toward H and supporting the existence of a radio halo; (2) an injection electron spectrum with a single power law up to the lowest energies cannot explain the radio observations satisfactorily in terms of the diffusion model; and (3) the observed spectral steepening can be satisfactorily understood as being due partly to the deviation from a power-law injection spectrum below a few GeV and partly to the first break arising from electron energy losses in approximately the same energy region.

Badhwar, G. D.↗
NASA NTRS1977

Radio and optical observations in the fields of five unidentified X-ray sources at high latitudes

Radio observations at 610 MHz and optical plates were obtained for five fields centered on the unidentified X-ray sources 3U0042 + 32, 3U0917 + 63, 3U1443 + 43, 3U1555 + 27, and 3U1809 + 50. For the first three fields, several radio sources are found which are associated with stellar objects within or near the X-ray error boxes. A 'tailed' radio galaxy has been found in Abell 2142, and this cluster is suggested as the identification for 3U1555 + 27. Although there are no radio sources greater than 0.1 flux unit within the X-ray error boxes associated with 3U1809 + 50, a Zwicky cluster surrounding the 3U position contains two radio galaxies: one with an inverted spectrum and another with a wide-angle tail. A table of positions, intensities, and suggested optical identifications is given for the 249 radio sources detected in the five fields.

Harris, D. E.↗
NASA NTRS1977

Interpretation of cosmological information on radio sources

The question of whether any cosmological information can be obtained from radio astronomy is considered. Specific attention is given to the discovery and cosmological interpretation of the microwave background radiation, attempts to derive a Hubble relation for the optical objects identified with radio sources, searches for relations between the angular diameters of radio sources and the redshifts of their optically identified counterparts as well as between angular diameter and radio flux, construction of log N - log S curves, and luminosity volume tests. A brief outline is given of the situation that might prevail if a significant population of radio sources is not at great distances and is associated with QSOs that have been ejected from relatively nearby galaxies. It is concluded that: (1) some types of cosmological investigations have been premature; (2) much of the discussion in this area still depends on the distances of QSOs; and (3) there is no conclusive proof that the population of radio sources is changing with epoch.

Burbidge, G.↗
NASA NTRS1978

Radio and X-ray variability of the nucleus of Centaurus A /NGC 5128/

Centaurus A (NGC 5128) has been observed at radio frequencies of 10.7, 31.4, 85.2, and 89 GHz and at X-ray energies greater than 20 keV. These observations, together with results reported by other workers, are interpreted in terms of models of the nucleus of this radio galaxy. The radio observations cover the period from 1973 through early 1977. The X-ray observations cover two 10-day intervals, one in July and August (1975) and the other in July and August 1976. The source exhibits significant variability in all the observed radio frequencies. The observed radio and X-ray intensities show some concurrent variations but do not track one another throughout the observations. A model of the source in which X-rays are produced by inverse Compton scattering of blackbody photons by relativistic electrons is proposed to explain these observations. The observed variations in the electromagnetic spectrum are shown to be consistent with adiabatic expansion of a trapped plasma in conjunction with turbulent accelerations of the relativistic electrons. Upper limits obtained with the model indicate that there may be sufficient energy available in the nucleus to form radio lobes with the same total energy as those already present.

Beall, J. H.↗
NASA NTRS1978

Propagation of cosmic rays in extragalactic radio sources

A model of extragalactic radio sources is considered which assumes that relativistic electrons carry energy from the central galaxy to the radio lobes and also emit the radio waves. It is suggested that the radio emission is confined to an axis because electrons propagate parallel to the magnetic field more readily than perpendicular to it and that symmetric radio lobes appear on this axis because electrons are deposited at supercoherent transitions far from the central galaxy, where they propagate diffusively. The slow drift velocities that characterize this propagation are shown to explain the secondary structure between the main lobes and to establish a relationship between double sources and galactic radio trails.

Earl, J. A.↗
NASA NTRS1981

Effects of gamma-ray, neutrino, and particle production on the energetics and dynamics of compact extragalactic radio sources

Consideration is given to particle production and high-energy radiation within apparently superluminal radio components of extragalactic radio sources forming within the apparent region of nuclear activity of a quasar or active galaxy. The physical conditions in compact components observed as radio emitters are derived for the quasars 3C 273 and 3C 345 and extrapolated to those of initial components of sizes on the order of 10 to the 15th cm on the basis of two-dimensional relativistic jet and relativistic three-dimensional models of component expansion. Probabilities that a given particle avoids an inelastic collision in the relativistic plasma are calculated for both cases which show that collisions which produce particles and radiation may be very important during the formation of a compact radio component. The consequences of electron-positron production, bremsstrahlung and proton-proton inelastic collisions ultimately giving rise to neutrinos and gamma rays for the development and energetics of the radio component are then examined, and upper limits to the amount of energy which can be channeled into radio components from an active region without giving rise to a high-energy X-ray source are derived.

Vestrand, W. T.↗
NASA NTRS1982

Radio jets in NGC 4151

The relationship between the radio and optical emissions from the nucleus of the Seyfert galaxy NGC 4151 is investigated by mapping the radio radiation from this source at wavelengths of 20 and 6 cm using the Very Large Array of the National Radio Astronomy Observatory. Results show that the radio emission at wavelengths from 20 to 6 cm extend 10'' (950 pc) along a position angle of 72-84 degrees. This nonthermal emission is found to consist of at least six components and is similar to jets observed in other compact extragalactic radio sources. These radio jets appear to be coincident with the optical line emission region in NGC 4151 and are aligned with the position angle of the linearly polarized optical continuum emission.

Johnston, K. J.↗
NASA NTRS1983

X-ray, radio, and infrared observations of the 'rapid burster' /MXB 1730-335/ during 1979 and 1980

The paper reports partially simultaneous observations of the 'rapid burster' (MXB 1730-335) at X-ray, infrared, and radio wavelengths, covering several hundred hours during 1979 and 1980. None of the authors of this report saw any infrared or radio bursts. On several occasions an absence of infrared bursting was observed during X-ray bursting. On one occasion an absence of X-ray bursting was observed during a radio burst (4.1 GHz) reported by Calla et al. (1979). To date, radio bursts (a total of at least a dozen) have been reported only by Calla et al. (1980). Considering these and other observations summarized here, the reported radio bursts are either unreal or do not bear a simple relation to the X-ray bursts from the 'rapid burster'. The status of the reported infrared bursts also remain ambiguous. Limits to the brightness of any persistent radio source at the position of MXB 1730-335, limits to persistent X-ray emission during an extended X-ray quiet phase, and a measurement of the infrared polarization in the direction of the X-ray source are also reported.

Lawrence, A.↗
NASA NTRS1984

Decimetric type III radio bursts and associated hard X-ray spikes

For a relatively weak solar flare on August 6, 1981, at 10:32 UT, a detailed comparison is made between hard X-ray spikes and decimetric type III radio bursts. The hard X-ray observations are made at energies above 30 keV, and the radio data are obtained in the frequency range from 100 to 1000 MHz. The time resolution for all the data sets is approximately 0.1 s or better. The dynamic radio spectrum exhibits many fast drift type III radio bursts with both normal and reverse slope, whereas the X-ray time profile contains many well resolved short spikes with durations less than or equal to 1 s. Some of the X-ray spikes are seen to be associated in time with reverse-slope bursts, indicating either that the electron beams producing the radio burst contain two or three orders of magnitude more fast electrons than has previously been assumed or that the electron beams can induce the acceleration of additional electrons or occur in coincidence with this acceleration. A case is presented in which a normal slope radio burst at approximately 600 MHz occurs in coincidence with the peak of an X-ray spike to within 0.1 s.

Dennis, B. R.↗
NASA NTRS1982

Interplanetary radio storms. 2: Emission levels and solar wind speed in the range 0.05-0.8 AU

Storms of interplanetary type III radio bursts (IP storms) are commonly observed in the interplanetry medium by the ISEE-3 radio instrument. This instrument has the capability of accurately determining the arrival direction of the radio emission. At each observing frequency, the storm radio sources are tracked as they cross the line-of-sight to the Sun. Usng a simple model, the emission levels are determined at a number of radio frequencies for four separate storms. The IP storm radiation is found to occur in regions of enhanced density at levels of 0.05 to 0.8 AU. The density in these enhancements falls off faster than R(-2). The solar wind speed in the storm region is also measured. The analysis is consistent with steady conditions in the storm region during a few days around the central meridian passage of the storm. The comparison with average in situ density measurements compiled from the HELIOS 1-2 observations favors type III storm burst radio emission at the harmonic of the local plasma frequency.

Bougeret, J. L.↗
NASA NTRS1985

Nonthermal Radio Emission and the HR Diagram

Perhaps the most reliable indicator of non-radiative heating/momentum in a stellar atmosphere is the presence of nonthermal radio emission. To date, 77 normal stellar objects have been detected and identified as nonthermal sources. These stellar objects are tabulated herein. It is apparent that non-thermal radio emission is not ubiquitous across the HR diagram. This is clearly the case for the single stars; it is not as clear for the binaries unless the radio emission is associated with their late-type components. Choosing to make this association, the single stars and the late-type components are plotted together. The following picture emerges: (1) there are four locations on the HR diagram where non-thermal radio stars are found; (2) the peak incoherent 5 GHz luminosities show a suprisingly small range for stars within each class; (3) the fraction of stellar energy that escapes as radio emission can be estimated by comparing the integrated maximum radio luminosity to the bolometric luminosity; (4) there are no apparent differences in L sub R between binaries with two cool components, binaries with one hot and one cool component, and single stars for classes C and D; and (5) The late-type stars (classes B, C, and D) are located in parts of the HR diagram where there is reason to suspect that the surfaces of the stars are being braked with respect to their interiors.

Gibson, D. M.↗
NASA NTRS1984

Interplanetary radio storms. II - Emission levels and solar wind speed in the range 0.05-0.8 AU

Storms of interplanetary type III radio bursts (IP storms) are commonly observed in the interplanetary medium by the ISEE-3 radio instrument. This instrument has the capability of accurately determining the arrival direction of the radio emission. At each observing frequency, the storm radio sources are tracked as they cross the line-of-sight to the sun. Using a simple model, the emission levels are determined at a number of radio frequencies for four separate storms. The IP storm radiation is found to occur in regions of enhanced density at levels of 0.05 to 0.8 AU. The density in these enhancements falls off faster than R(-2). The solar wind speed in the storm region is also measured. The analysis is consistent with steady conditions in the storm region during a few days around the III storm burst radio emission at the harmonic of the local plasma frequency.

Bougeret, J.-L.↗
NASA NTRS1985

X-rays from the radio halo of Virgo A = M87

The purpose of this study is to investigate in more detail the associated X-ray and radio emission in the Virgo A halo discovered by SGF. Improved Einstein HRI data and new radio maps obtained with the Very Large Array are described and the relation between the X-ray and radio structures is carefully examined. Several possible explanations are presented for the X-ray emission. The inverse compton model is found to be viable only if the magnetic field is variable and substantially weaker than the equipartition value. The principal alternative is excess thermal X-rays due to compression of the intracluster medium by the radio lobe. In either case, the association of such prominent radio and X-ray structures is unique among known radio galaxies.

Source record↗
NASA NTRS1987

Radio and infrared observations of (almost) one hundred non-Seyfert Markarian galaxies

The 13 cm flux densities of 96 non-Seyfert Markarian galaxies were measured at Arecibo Observatory. Far infrared flux densities have been published for 78 of these galaxies in the IRAS catalog. The radio, infrared, and optical fluxes of these galaxies and of a magnitude limited sample of normal galaxies were compared to clarify the nature of the radio emission in Markarian galaxies. It was found that Markarian galaxies of a given apparent magnitude and Hubble type generally have radio fluxes several times higher that the fluxes typical of normal galaxies of the same magnitude and type. Remarkably, the ratio of radio flux to far infrared flux is nearly the same for most of these starburst galaxies and for normal spiral disks. However, the compact and peculiar Markarian galaxies consistently have about 60% more radio flux per unit infrared flux than the other Markarian galaxies and the normal spirals. It is not clear whether this difference reflects a difference in the evolution of the starbursts in these galaxies or whether there is excess radio emission of nonstellar origin.

Dressel, Linda L.↗