Multiple scattering of HF surface waves: implications for radar design and sea clutter interpretation

The interpretation of HF surface wave radar echoes is carried out, implicitly or explicitly, in the context of a physical model of the observation process on whose validity the verisimilitude of the interpretation depends. Hitherto it appears to have been near-universal practice to assume that the signal incident on any spatial cell being interrogated is a scaled, delayed version of the transmitted signal, arriving along the geodesic connecting the location of the transmitter with that of the cell. In this study, the authors describe a model that takes into account the changes to the radar signal as it propagates across the moving sea surface and show that the resulting redistribution of signal energy over the time delay, Doppler and direction-of-arrival dimensions can deviate markedly from that assumed by the idealised model. The authors investigate the dependence of the redistribution on radar and environmental parameters and provide what they hope will be useful guiding principles which can be employed to circumvent, or at least minimise, the short-comings of existing designs.