The Influence of Specular Reflections on Bistatic Tropospheric Radio Scatter from Turbulent Strata

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  • 1 Dept. of the Geophysical Sciences, The University of Chicago
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Abstract

Specular reflection from a stratum of sharp, mean, vertical refractivity gradient frequently accompanies the scatter from the turbulent perturbations in refractivity which tend to be maximized close to the gradient. As a result, the signal intensity falls more rapidly, and the magnitude of the mean Doppler shift increases less rapidly with beam offset angle from the great circle than is the case for pure turbulent scatter. Also, in transmission via the great circle path, the Doppler spread, signal fading rate, and multi-path spread may be greatly reduced from that expected for turbulent scatter alone. Because transmission along the great circle may be greatly influenced by specular reflections, the strength of which is a function of the form and sharpness of the mean refractivity gradient, past experiments relating signal-wavelength dependence or signal-scatter angle dependence to the form of the turbulent refractivity spectrum are suspect.

Abstract

Specular reflection from a stratum of sharp, mean, vertical refractivity gradient frequently accompanies the scatter from the turbulent perturbations in refractivity which tend to be maximized close to the gradient. As a result, the signal intensity falls more rapidly, and the magnitude of the mean Doppler shift increases less rapidly with beam offset angle from the great circle than is the case for pure turbulent scatter. Also, in transmission via the great circle path, the Doppler spread, signal fading rate, and multi-path spread may be greatly reduced from that expected for turbulent scatter alone. Because transmission along the great circle may be greatly influenced by specular reflections, the strength of which is a function of the form and sharpness of the mean refractivity gradient, past experiments relating signal-wavelength dependence or signal-scatter angle dependence to the form of the turbulent refractivity spectrum are suspect.

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