Small scale antenna diversity as a means of reducing the effects of multipath fading for handheld satellite communications systems

Abstract

This document discusses the measurements conducted at Virginia Tech, in Blacksburg, VA, and at COMSAT Labs, in Clarksburg MD, to determine the impact of multipath fading upon a circularly polarized L-Band satellite-to-handheld communications system using an omni-directional antenna. A significant finding was that motion of the satellite could induce fades of up to lOdB, well in excess of the small link margins available to satellite-to-handheld systems (typically ≤ 3dB). A method for ameliorating multi path fading was then sought. It was also found that the multipath fading effect was significantly different at as small a distance as half a wavelength from the original antenna position. Multipath signals could actually combine at the new position to form a small increase in signal to noise ratio (S/N), rather than a fade of as much as 16dB. Therefore it was determined that a small-scale antenna diversity system might offer a solution to the problem of multipath fading.