Accession Number : AD0803434

Title :   POWER PATTERN DEGRADATION FOR WEIGHTED CIRCULAR APERTURES IN A TURBULENT ATMOSPHERE.

Descriptive Note : Rept. for Dec 65-May 66,

Corporate Author : AEROSPACE CORP EL SEGUNDO CA LABS DIV

Personal Author(s) : Heidbreder, Glenn R. ; Mitchell, Richard L.

Report Date : SEP 1966

Pagination or Media Count : 13

Abstract : Average power patterns are calculated for weighted circular apertures in a turbulent medium. The turbulence is assumed to be locally homogeneous and the aperture diameters treated are such that they fall within the inertial subrange of the Obukhov-Kolmogorov theory of turbulence. Calculations are performed both for fixed apertures and for apertures which track wavefront tilt in such a manner that alignment with the direction of maximum power is maintained. They are based on supporting analyses which treat only phase perturbations due to the atmosphere, but have wide applicability because of the validity of ray optics in turbulent medium propagation where small perturbation theory is applicable to both phase and amplitude fluctuations. Curves showing percent half-power beambroadening and gain reduction as a function of degree of turbulence are also presented. The results show that pattern degradation is significantly less for tracking apertures than for fixed apertures. (Author)

Descriptors :   (*ANTENNA APERTURES, ATMOSPHERIC MOTION), (*ANTENNA RADIATION PATTERNS, ATMOSPHERIC MOTION), DEGRADATION, TRACKING, WAVE PROPAGATION, THEORY, TURBULENCE, ATTENUATION.

Subject Categories : Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE