NRL TERRAIN CLUTTER STUDY, PHASE 1
NAVAL RESEARCH LAB WASHINGTON DC
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The first phase of a terrain-clutter study has been completed at NRL, utilizing the four-frequency radar system installed in a WV2-128324 Super Constellation aircraft. This system is capable of transmitting and receiving four frequencies P, L, C, and X consecutively with a choice of horizontal, vertical, and alternating polarizations. The returns are gated at a fixed range and analyzed in a digital computer. Absolute clutter measurements have taken over both Canadian and American sites at angles of incidence of 10 degrees or less. Two parameters have been measured. The first is the normalized radar cross section in terms of the 10, 50 median, and 90 percentile values of its distribution, while the second is the fluctuation power spectrum of the coherent radar return signal. Two types of statistical processes have been determined from the cross-section data one follows a Rayleigh distribution between 10 and 90 percentile values, and one departs radically from this distribution. The energy in the fluctuation power spectrum has been estimated in frequency bands whose spacing is determined by the transmitted frequency, e. g., 2 cps at P band through 10 cps at X band. The root mean square deviations of the estimates indicate likewise a Rayleigh behavior for certain bands and a radical departure from this behavior. In this case, the radical departure is identified as a Ricean signal plus noise distribution produced by strongly reflecting point targets in the illuminated area. A statistical model for terrain clutter is proposed which will enable the phenomenon disclosed by the study to be simulated based upon the optical analysis of Synthetic Aperture Radar Maps.
- Active and Passive Radar Detection and Equipment