Millimeter wave scattering by rain in an antenna's near field

One of the important considerations in radio link analysis is the signal degradation that accompanies rainfall in a link’s path. Random scattering by rain can adversely affect a propagating wave in two ways. First, it results in attenuation and depolarization of the coherent field which is associated with the forward propagating wave. ln addition to this, random scattering gives rise to an incoherent field component that can further degrade the signal in a manner similar to multipath. This dissertation presents an analysis of the coherent and incoherent effects of rain scatter at millimeter-wave frequencies. Within it, the scattering properties of individual spherical and non-spherical are quantified. Spherical raindrops are treated using the Mie theory and non-spherical ones analyzed with Waterman’s Extended Boundary Condition Method. Computed values of forward scattering amplitudes and scattering cross-sections for both spherical and non-spherical raindrops at 80, 45, 70 and 90 GHz are presented; the computer programs used to obtain the scattering data are also provided. Following the analysis of individual raindrops scatterers, the Foldy·Lax Twersky integral equations for coherent field and incoherent intensity are used to derive the coherent and incoherent outputs of a generic radio receiver. In doing so, the effects of scattering in an antenna’s far-field and radiating near field (Fresnel Region) are analyzed. Through this analysis, it is shown that the expected system outputs are essentially the same in either case. Using the computed raindrop scattering parameters and models developed for the coherent and Incoherent system outputs, specific cases are Iooked at for 30, 45, 70 and 90 GHz operation and theoretical data presented. The data consists of the predicted attenuation and Isolation of the coherent signal and the ratio of coherent to Incoherent power In the presence of rain. From the latter it Is found that during heavy rainfall, the Incoherent effects can be appreciable and should be taken into account.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Electrical Engineering

Department dc:contributor.department

Electrical Engineering

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1988

Author dc:creator

• Barksdale, Harry

Chair dc:contributor.committeechair

• Bostian, Charles

Committee members dc:contributor.committeemember

• Stutzman, Warren L.
• Pratt, Timothy
• de Wolf, David A.
• Kohler, Werner

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/53906

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/53906