Radio Science

VHF radar sea scatter and propagation at grazing angles less than 1°


  • R. H. Ott,

  • M. A. Pollock,

  • R. J. Dinger,

  • T. E. Tice


Measurements of low grazing angle radar sea backscatter and multipath in the frequency range from 30 to 300 MHz, along with the supporting theoretical modeling, have been lacking because of the practical difficulties associated with fielding radars in this band. An ultrawideband (UWB) radar that radiates waveforms encompassing this band has recently been installed at a seaside location near the Naval Research and Development facility, Pt. Loma, San Diego, California. Propagation path loss measurements were performed at 40, 90, 140, and 190 MHz. Broadband clutter measurements were performed over the frequency band 200 to 300 MHz. The theoretical model is based on an integral equation solution for the surface fields. The surface fields are obtained using a new mathematical derivation of the integral equation for the surface fields (Ott, 1992). This new integral equation extends the frequency range of the former algorithm, WAGNER, to the VHF band. The surface fields are then integrated to obtain either the forward scatter (multipath) or the backscatter (clutter).