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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

The definition of cross polarization.

Consideration of three alternate definitions of cross-polarization known to the author. The three definitions are expressed precisely in terms of the same antenna pattern coordinate system, and the relative merits of the various definitions are discussed. One of the definitions is shown to be the proper choice for describing source current polarizations, another is suitable for relating source current distributions to secondary patterns, and the third is the best choice for describing antenna patterns.

Ludwig, A. C.↗
NASA NTRS1979

CTS attenuation and cross polarization measurements at 11.7 GHz

Attenuation and cross-polarization isolation at 11.7 GHz, measured at Austin, Texas by receiving the circularly polarized emissions from the CTS satellite are presented. A 12 month summary for Feb 78 to Jan 79 is presented. For .016 percent of the time the attenuation was greater than 10 dB, the isolation was less than 21 dB and the rainrate exceeded 55 mm/hr. Ice depolarization was observed frequently.

Vogel, W. J.↗
NASA NTRS1973

Surface configuration as an explanation for lithology-related cross-polarized radar image anomalies

One problem that has persisted since the development of multipolarized radar is the cause or causes of differential depolarization which is expressed as tonal reversals between like- and cross-polarized images of certain outcrops. Rocks producing anomalously low returns on the cross-polarized image could be classed into three general types: (1) certain geologically recent lava flows (late Pleistocene and Holocene), (2) some tertiary volcanics and (3) certain massive sandstones. Differential depolarization has been produced by volcanic rocks of various compositions including rhyolite, rhyodacite, dacite, andesite, and basalt. This has led to the conclusion that differential depolarization is not directly caused by any compositional factor. However, the study of aerial photos and subsequent field observation have led to the conclusion that the weathering and other surface characteristics of the outcrops are responsible for their appearance on multipolarized imagery.

Mccauley, J. R.↗
NASA NTRS1977

CTS attenuation and cross-polarization measurements at 11.7 GHz

The results of data obtained 80 days preceding the solar eclipse shutdown of the CTS 11.7 GHz righthand circularly polarized beacon transmitter are presented. Attenuation and cross polarization isolation were measured. It was determined that depolarization presents a serious limitation to satellite system reliability when frequency reuse by polarization diversity is employed. A 27 db isolation margin would reduce reliability below 99.95%. For the same percentage the required fade margin was below 3 db.

Vogel, W. J.↗
NASA NTRS2002

On the cross-polarization characteristics of crooked wire antennas designed by genetic-algorithms

In many modern communication applications there is a need for simple circularly polarized antennas for hemispherical coverage with good axial ratio or low value of cross polarization. We revisited the crooked wire antenna because of its simplicity. This paper presents results of our investigation on the crooked wire antennas and other elements.

genetic algorithms communications crooked wire ant↗
NASA NTRS1980

CTS attenuation and cross polarization measurements at 11.7 GHz

The long-term attenuation, cross-polarization, and rain-rate data monitored in Austin, Texas from the circularly polarized 11.7 GHz satellite beacon transmitter aboard the Communications Technology Satellite are analyzed. Data events are significantly more likely during April-September, than during October-March, except for ice deplorization which predominates during the winter months. A time of day dependence of the events is also noted. The 10 dB fade level is exceeded for .03% during the thunderstorm months. Isolation with the same probability is 23 dB.

Vogel, W. J.↗
NASA NTRS1984

Cross-polar cap potential drop and the energy coupling function

A numerical model is formulated for correlations between the cross polar cap potential, the solar wind, and the AI index and compared with satellite data. The conductivity model was devised from empirically defined relationships between the Hall and Pedersen conductivities and the measured magnitude of the horizontal magnetic disturbance near College, AK. An instantaneous conductivity distribution was generated from data gathered at, e.g., six IMS meridian chain stations. A strong correlation appeared between an energy coupling function (ECF) and the polar cap potential drop. The ECF was derived from the chain station data, implying that potential drop estimates can be made from ground-based magnetometer data.

Ahn, B.-H.↗
NASA NTRS1984

The relationship of rain-induced cross-polarization discrimination to attenuation for 10 to 30 GHz earth-space radio links

Rain depolarization is quantified through the cross-polarization discrimination (XPD) versus attenuation relationship. Such a relationship is derived by curve fitting to a rigorous theoretical model (the multiple scattering model) to determine the variation of the parameters involved. This simple isolation model (SIM) is compared to data from several earth-space link experiments and to three other models.

Stutzman, W. L.↗
NASA NTRS1978

CTS attenuation and cross polarization measurements at 11.7 GHz

The results of data obtained at The University of Texas at Austin during a total of 551 days of righthand circularly polarized transmission at 11.7 GHz from the CTS satellite are presented. Measured were attenuation, cross-polarization and rain rate. Results indicate that ice depolarization can be of significant importance.

Vogel, W. J.↗
NASA NTRS1987

Cross-polarized interferometry of a Jovian decametric radio storm

Observations of an 18-MHz Io-A storm have been conducted using a 46 km cross-polarized interferometer at the University of Florida. The pre- and postdetection correlation properties of LH and RH elliptically polarized L bursts have been studied. Fringe visibility measurements suggest that two discrete and independent sources are sometimes simultaneously active, the polarization sense of one being LH and that of the other RH. A scintillation analysis supports the conclusion that two or more sources were active in such cases.

Phillips, J. A.↗
NASA NTRS1996

Ray Scattering by an Arbitrarily Oriented Spheroid: 2. Transmission and Cross-polarization Effects

Transmission of an arbitrarily polarized plane wave by an arbitrarily oriented spheroid in the short-wavelength limit is considered in the context of ray theory. The transmitted electric field is added to the diffracted plus reflected ray-theory electric field that was previously derived to obtain an approximation to the far-zone scattered intensity in the forward hemisphere. Two different types of cross-polarization effects are found. These are: (a) a rotation of the polarization state of the transmitted rays from when they are referenced with respect to their entrance into the spheroid to when they are referenced with respect to their exit from it and (b) a rotation of the polarization state of the transmitted rays when they are referenced with respect to the polarization state of the diffracted plus reflected rays.

Lock, James A.↗