Rake Probing of Atmospheric Refractive Structure

Abstract

Some aspects of atmospheric structure can be studied by the Rake technique which consists in transmitting a pseudo-random sequence of pulses from one end of a troposcatter link and correlating the received sequence with a locally generated identical pseudo-random sequence of pulses which has been delayed by known amounts. The Fourier transform of the resulting autocorrelation function gives the Doppler spectrum. The delay-Doppler plot, consisting of a number of Doppler spectra plotted for different delays, is called the scattering function. A number of scattering functions have been plotted for the Kanpur-Nainital troposcatter link to study the effects of heights and thicknesses of scattering layers, strength of scattering layer, anisotropy of scatterers, wind velocity, and wave number dependence on the scattering function. The study shows that the power received is very sensitive to the scattering model, anisotropy of scatterers, and the number of scattering layers. The shape of the spectrum reveals the layer thickness, anisotropy, and antenna offset.

Indexing Terms:

• Atmospheric Refraction
• Rake Probing
• Troposcatter Link