Sea spike demographics at high range resolutions and very low grazing angles

Abstract

Because the wideband spiky sea clutter that is frequently observed at low grazing angles and high resolution plays a critical role in the performance of modern naval radars, it is necessary to analyze two important quantities: (1) the mean spike duration and (2) the mean interval between spikes. These analyses need to be conducted with representative examples of such wideband clutter taken from a suitable database. Microwave backscatter (X-band, 9.5-10.0 GHz) observed at near grazing incidence (0.2 degrees) from the sea off the coast of Kauia, Hawaii, was measured with a wideband radar characterized by a high spatial resolution in range (0.3 meters) and a high temporal resolution (2000 Hz pulse repetition frequency). Extensive amounts (over 20 minutes duration per measurement) of both vertically and horizontally polarized wideband sea clutter data were taken with upwind and crosswind transmit geometries during the data collection exercise. The analyses of the dependence of the mean spike duration and the mean interval between spikes upon three parameters: (1) the spike amplitude threshold, (2) the minimum spike width, and (3) the minimum interval between spikes, were carried out. This was done using all of the extensive data within a number of selected individual range cells for both vertically and horizontally polarized clutter, measured with an upwind transmit geometry.