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Stutzman, W. L.

Publications and source records attributed to Stutzman, W. L..

53 records · Page 3
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NASA NTRS1976

Measurements of rain effects on an 18-GHz dual-polarized propagation link

The paper presents highlights of rain attenuation and depolarization data collected between August 1972 and March 1974 in an experimental setup consisting of a 1.43-km line-of-sight path with 1.22-m diam dual-polarized parabolic reflector antennas at each end. The antennas used question-mark mounted scalar feeds oriented to transmit or receive linearly polarized 17.65-GHz signals having electric field vectors at +45 deg and -45 deg from the vertical. Rain data were collected and analyzed for 24 individual storms in which the rain rate exceeded 10 mm/hr. Received signal levels were sampled once each second and stored by a small digital computer which controlled the experiment and performed preliminary data processing. The results are compared with a theoretical model presented by Wiley et al. (1974). Experimental cross-polarization isolation data are found to agree well with theoretical values, especially at high rain rates where the antenna effects are the least significant.

Bostian, C. W.↗
NASA NTRS1976

A depolarization and attenuation experiment using the CTS satellite. Volume 1: Experiment description

An experiment for measuring precipitation attenuation and depolarization on the Communications Technology Satellite (CTS) 11.7 GHz downlink is described. Attenuation and depolarization of the signal received from the spacecraft is monitored on a 24 hour basis. Data is correlated with ground weather conditions. Theoretical models for millimeter wave propagation through rain are refined for maximum agreement with observed data. Techniques are developed for predicting and mimimizing the effects of rain scatter and depolarization on future satellite communication systems.

Bostian, C. W.↗
NASA NTRS1975

Radiation pattern synthesis of planar antennas using the iterative sampling method

A synthesis method is presented for determining an excitation of an arbitrary (but fixed) planar source configuration. The desired radiation pattern is specified over all or part of the visible region. It may have multiple and/or shaped main beams with low sidelobes. The iterative sampling method is used to find an excitation of the source which yields a radiation pattern that approximates the desired pattern to within a specified tolerance. In this paper the method is used to calculate excitations for line sources, linear arrays (equally and unequally spaced), rectangular apertures, rectangular arrays (arbitrary spacing grid), and circular apertures. Examples using these sources to form patterns with shaped main beams, multiple main beams, shaped sidelobe levels, and combinations thereof are given.

Stutzman, W. L.↗
NASA NTRS1975

A 20 Ghz Depolarization Experiment Using the ATS-6 Satellite

A depolarization experiment using the 20 GHz downlink from the ATS-6 satellite was described. The following subjects were covered: (1) an operational summary of the experiment, (2) a description of the equipment used with emphasis on improvements made to the signal processing receiver used with the ATS-5 satellite, (3) data on depolarization and attenuation in one snow storm and two rain storms at 45 deg elevation, (4) data on low angle propagation, (5) conclusions about depolarization on satellite paths, and (6) recommendations for the depolarization portion of the CTS experiment.

Bostian, C. W.↗
NASA NTRS1975

Depolarization measurements on the ATS-6 20 GHz downlink A description of the VPI&SU experiment and some initial results

The experiment considered is mainly concerned with the depolarizing effects of precipitation at millimeter wavelengths. Excessive depolarization introduces cross talk into communication systems which employ orthogonal polarization for frequency reuse. An understanding of atmospheric depolarization phenomena is, therefore, required for the design of future earth-satellite communications systems. Attenuation and cross polarization ratio data obtained under various meteorological conditions, including rain and a snowstorm, are presented.

Bostian, C. W.↗
NASA NTRS1974

The influence of polarization on millimeter wave propagation through rain

The influence of polarization on millimeter wave propagation through rain is investigated. The experimental equipment consisted of a 1.43 km line-of-sight path with 4-foot diameter dual-polarized parabolic reflector antennas at each end. Linearly polarized 17.65 GHz signals were transmitted with the electric field vectors at plus 45 degrees and minus 45 degrees from the vertical. These polarizations were initially chosen to maximize the measured depolarization at any given rainfall rate. Later it was discovered that the cross polarization levels measured with plus or minus 45 degree linearly polarized signals are theoretically the least sensitive to variations in drop canting angle and this choice of polarization reduces the scatter in the data.

Bostian, C. W.↗
NASA NTRS1974

The influence of polarization on millimeter wave propagation through rain

The limitations which precipitation depolarization will place on future millimeter wave earth-satellite communications systems employing orthogonal-polarization frequency sharing was studied and the possibility of improving the fade resistance of such systems either through polarization diversity operation or by the choice of the polarization(s) least subject to attenuation was examined. Efforts were confined largely to ground-based communications systems investigated during a twenty-seven month period. Plans to extend the theoretical results to satellite systems are discussed.

Bostian, C. W.↗
NASA NTRS1973

Synthesis of multiple shaped beam antenna patterns

Results are presented of research into the problem of finding an excitation of a given antenna such that the desired radiation pattern is approximated to within acceptable limits. This is to be done in such a fashion that boundary conditions involving hardware limitations may be inserted into the problem. The intended application is synthesis of multiple shaped beam antennas. Since this is perhaps the most difficult synthesis problem an antenna engineer is likely to encounter, the approach taken was to include as a by-product capability for synthesizing simpler patterns. The synthesis technique has been almost totally computerized. The class of antennas which may be synthesized with the computer program are those which may be represented as planar (continuous or discrete) current distributions. The technique is not limited in this sense and could indeed by extended to include, for example, the synthesis of conformal arrays or current distributions on the surface of reflectors. The antenna types which the program is set up to synthesize are: line source, rectangular aperture, circular aperture, linear array, rectangular array, and arbitrary planar array.

Stutzman, W. L.↗
NASA NTRS1973

The influence of polarization on millimeter wave propagation through rain

The measurement and analysis of the depolarization and attenuation that occur when millimeter wave radio signals propagate through rain are described. Progress was made in three major areas: the processing of recorded 1972 data, acquisition and processing of a large amount of 1973 data, and the development of a new theoretical model to predict rain cross polarization and attenuation. Each of these topics is described in detail along with radio frequency system design for cross polarization measurements.

Bostian, C. W.↗
NASA NTRS1973

The influence of polarization on millimeter wave propagation through rain

The influence of polarization on millimeter wave propagation is investigated from both an experimental and a theoretical viewpoint. First, previous theoretical and experimental work relating to the attenuation and depolarization of millimeter waves by rainfall is discussed. Considerable detail is included in the literature review. Next, a theoretical model is developed to predict the cross polarization level during rainfall from the path average rain rate and the scattered field from a single raindrop. Finally, data from the VPI and SU depolarization experiment are presented as verification of the new model, and a comparison is made with other theories and experiments. Aspects of the new model are: (1) spherical rather than plane waves are assumed, (2) the average drop diameter is used rather than a drop size distribution, and (3) it is simple enough so that the effect which changing one or more parameters has on the crosspolarization level is easily seen.

Wiley, P. H.↗
NASA NTRS1973

Beam-pointing errors of planar-phased arrays.

Using both analytical and Monte Carlo techniques, beam-pointing errors of planar-phased arrays are analyzed. The obtained simple formulas for rms pointing errors are applicable to uniform planar arrays with both uniform and Gaussian uncorrelated phase-error distributions and for any arbitrary scan angle.

Carver, K. R.↗
NASA NTRS1973

A scattering model for rain depolarization

A method is presented for calculating the amount of depolarization caused by precipitation for a propagation path. In the model the effects of each scatterer and their interactions are accounted for by using a series of simplifying steps. It is necessary only to know the forward scattering properties of a single scatterer. For the case of rain the results of this model for attenuation, differential phase shift, and cross polarization agree very well with the results of the only other model available, that of differential attenuation and differential phase shift. Calculations presented here show that horizontal polarization is more sensitive to depolarization than is vertical polarization for small rain drop canting angle changes. This effect increases with increasing path length.

Wiley, P. H.↗
NASA NTRS1973

Recent advances in antenna synthesis.

A technique for the synthesis of planar aperture antennas has been developed. It applies equally well to continuous or array type apertures. Patterns with shaped main beams and complex sidelobe structures can be synthesized. The method involves applying corrections iteratively and converging toward the desired pattern. The iteration process terminates when the synthesized pattern approximates the desired pattern to within a specified tolerance. A computer program has been written to perform all calculations. The source distribution which is required to produce the synthesized pattern is provided as output. The method is such that patterns requiring complex source distributions will not be synthesized (such as superdirective patterns).

Stutzman, W. L.↗
NASA NTRS1972

The influence of polarization on millimeter wave propagation through rain

A program for the measurement and analysis of the depolarization and differential attenuation that occur when millimeter wave signals propagate through rain is described. Initial data are taken along a 1.43 km path at 17.65 GHz and a supporting theoretical model is developed to relate the propagation effects to rainfall rate and wind velocity. A block diagram of the overall experiment is included. It consists of: (1) an RF system (millimeter wave transmitter and receiver), (2) transmitting and receiving antennas, (3) a weather system with rain gauges, wind sensors, and drop counters, and (4) a digital control, processing, and data storage system.

Bostian, C. W.↗