Multipath-abating antenna system for line-of-sight communications above an air-sea water interface

This paper describes a multipath-abating antenna system consisting of a linear array of four quadrifilar helical antenna (QHA) elements and an associated beamformer that are installed on a buoy that floats along the sea surface for the purpose of supporting both transmit and receive communications along line-of-sight paths. The circuit and radiation characteristics of a QHA enable an array of these antennas to provide hemispherical coverage overhead with sufficient gain and low sensitivity to multipath interference. In the receive mode, the beamformer takes advantage of the spatial diversity of the array by appropriately weighting the elements in order to optimize the array signal-to-noise ratio.