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Author

W. J. Vogel

Bio: W. J. Vogel is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Polarization (waves) & Linear polarization. The author has an hindex of 3, co-authored 4 publications receiving 28 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the ATS 6 satellite was used to perform low angle of elevation measurements at 30 GHz with a 1.5 m antenna at Port Aransas, Texas, resulting in a propagation path entirely over water.
Abstract: The return of the ATS 6 satellite to a western longitude during the fall of 1976 presented a unique opportunity to perform low angle of elevation measurements at 30 GHz. For this purpose a receiver using a 1.5 m antenna was set up at Port Aransas, Texas, resulting in a propagation path entirely over water. The 30 GHz beacon was monitored daily for at least one hour from 8 September 1976 to 21 September 1976. During the time the elevation angle changed from 1.5 deg to 17.3 deg, the mean attenuation decreased from 20 dB to 2 dB and the standard deviation from over 6 dB to less than .2 dB. The deep fades at angles below 4 deg show significantly sharper nulls than peaks on a log scale. Spectra of the log amplitude fluctuations vary as the (-8/3) power of the spectral frequency in the limit. A flattening is noticeable at the low frequencies. A precipitation event at 8.5 deg elevation produced a 16 dB fade and significantly increased the variance.

12 citations

01 Nov 1975
TL;DR: The results of data obtained at The University of Texas at Austin in conjunction with the ATS-6 millimeter wave experiment are presented in this article, where attenuation measurements at 30 GHz and sky noise data at 20 GHz were obtained simultaneously at each of two sites separated by 11 km.
Abstract: The results of data obtained at The University of Texas at Austin in conjunction with the ATS-6 millimeter wave experiment are presented Attenuation measurements at 30 GHz and sky noise data at 20 GHz were obtained simultaneously at each of two sites separated by 11 km Space diversity reduces outage time for a system in Austin, Texas with a 10 dB fade margin at 30 GHz from 15 hours to 16 minutes per year The maximum cloud height shows a good correlation to the maximum attenuations measured

8 citations

Journal ArticleDOI
TL;DR: In this paper, the results of data obtained at The University of Texas at Austin in conjunction with the ATS-6 millimeter wave experiment are presented for 93 days simultaneously at each of two sites separated by 11 km and for 314 days at one site.
Abstract: The results of data obtained at The University of Texas at Austin in conjunction with the ATS-6 millimeter wave experiment are presented. Attenuation measurements at 30 GHz and sky noise data at 20 GHz were obtained for 93 days simultaneously at each of two sites separated by 11 km and for 314 days at one site. The ratio of the loss at 30 GHz to that at 20 GHz due to rain varied from about 2 to about 4 with a median value of 2.65. This value was used to estimate 30 GHz losses for the 38.6% of time during attenuation events for which the satellite link was not available. Space diversity reduced outage time for a system in Austin, Texas, with a 10 db fade margin at 30 GHz from 3.8 hours to 4.1 minutes for the 93 days. Extrapolated to a yearly base this corresponds to 15 hours and to 16 minutes respectively. A plot of maximum observed cloud height against maximum hourly attenuation indicates that for a given attenuation level a lower limit is set for the maximum cloud height.

7 citations

Book ChapterDOI
01 Jan 1976
TL;DR: In this paper, a theoretical investigation of cross polarization generation and radar echo cancellation for the propagation of electromagnetic waves at 17, 30 and 92 GHz through rain is carried out, both due to canted, nonspherical drops.
Abstract: A theoretical investigation of cross polarization generation and radar echo cancellation for the propagation of electromagnetic waves at 17, 30 and 92 GHz through rain is carried out. Both effects are due to canted, nonspherical drops. The canting angles are assumed random with preferred directions. The drop shapes used were determined at UCLA by Pruppacher, Beard and Pitter. They are oblate with increasingly flat and finally concave bottoms as drop size increases. The scattering from single particles is solved by point matching for arbitrary angles of incidence of a plane wave. Propagation through the anisotropic rain medium is handled mathematically with the use of the characteristic polarizations and propagation constants. Cross polarization effects for linear and circular transmit polarization and rain echo cancellations for circular polarization are found for rain rates up to 150 mm/hr and ranges up to 5 km. The cancellation is improved with non-circular radar polarization; however the optimum polarization is critically dependent upon the canting angle distribution.

1 citations


Cited by
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01 Feb 1989
TL;DR: The NASA Propagation Effects Handbook for Satellite Systems Design provides a systematic compilation of the major propagation effects experienced on space-Earth paths in the 10 to 100 GHz frequency band region.
Abstract: The NASA Propagation Effects Handbook for Satellite Systems Design provides a systematic compilation of the major propagation effects experienced on space-Earth paths in the 10 to 100 GHz frequency band region It provides both a detailed description of the propagation phenomenon and a summary of the impact of the effect on the communications system design and performance Chapter 2 through 5 describe the propagation effects, prediction models, and available experimental data bases In Chapter 6, design techniques and prediction methods available for evaluating propagation effects on space-Earth communication systems are presented Chapter 7 addresses the system design process and how the effects of propagation on system design and performance should be considered and how that can be mitigated Examples of operational and planned Ku, Ka, and EHF satellite communications systems are given

199 citations

Journal ArticleDOI
TL;DR: An empirical model has been generated to estimate diversity gain on earth-space propagation paths as a function of earth terminal separation distance, link frequency, elevation angle, and angle between the baseline and the path azimuth.
Abstract: An empirical model has been generated to estimate diversity gain on earth-space propagation paths as a function of earth terminal separation distance, link frequency, elevation angle, and angle between the baseline and the path azimuth. This analysis utilized 34 diversity experiments which have been conducted in Canada, England, Japan, and the United States during the past decade. The resulting model reproduces the entire experimental data set with an rms error of 0.73 dB. The separation distance dominates the dependence of the diversity gain. The dependence on link frequency is small but significant. No identifiable dependence on baseline orientation was found.

111 citations

Journal ArticleDOI
01 May 1978
TL;DR: In this paper, a review of the results known to the author, discusses the influence of various kinds of rainfall and analyses the principal causes giving rise to the variations in space-diversity performance.
Abstract: Space diversity (the simultaneous use through a common operations centre of two, or more, satellite receivers on the ground to overcome severe path attenuation that might occur on one of the links) is a well known concept and many measurements have been made to assess its potential advantages. The experimental results to date, however, show a large variability in space-diversity performance. The paper reviews all the results known to the author, discusses the influence of various kinds of rainfall and analyses the principal causes giving rise to the variations in space-diversity performance. Microclimate, receiver base-line orientation, site separation and topography are concluded to be the prime causes of the variations in measured space-diversity performance, and broad guidance for selecting the sites for a space-diversity complex is given.

29 citations

Journal ArticleDOI
TL;DR: In this paper, the long-wave cutoff in the spectrum of amplitude fluctuations was shown to be capable of explaining strong SHF scintillation in the troposphere, which is also applicable to strong VHF and EHF Scintillation.
Abstract: Ionization structure perpendicular to the line of sight can cause total internal reflection at glancing incidence, leading to refractive scattering that can dominate diffractive scattering The long-wave cutoff in the spectrum of amplitude fluctuations then occurs, not at the Fresnel scale but at a larger scale that increases as the percentage fluctuation of ionization density increases The additional amplitude fluctuation arising from the band of scales extending from the usual diffractive cutoff scale up to the refractive cutoff scale is capable of explaining strong SHF scintillation It also lowers the estimates of the fluctuation of ionization density needed to explain strong VHF scintillation The concept of refractive scattering is also likely to be applicable to SHF-EHF scintillation phenomena in the troposphere

28 citations

Journal ArticleDOI
TL;DR: In this paper, the results of a radar study of path diversity performance on simulated earth-space communication links in the presence of rainfall were presented, showing that path diversity is mildly dependent upon the orientation of the propagation path and weakly dependent on the baseline orientation of ground diversity terminals.
Abstract: This paper contains the results of a radar study of path diversity performance on simulated earth-space communication links in the presence of rainfall. The McGiIl University 3 GHz radar was used to obtain three-dimensional fields of radar reflectivity. The radar reflectivities measured at resolution cells along the propagation paths of interest were converted to specific attenuation and these values of specific attenuation were then summed to yield the total path attenuation. This procedure was repeated along parallel earth-space paths to yield the path diversity performance. The results for the Montreal area indicate that path diversity performance is mildly dependent upon the orientation of the propagation path and weakly dependent upon the baseline orientation of the ground diversity terminals.

27 citations