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This report determines how ground clutter strength varies with RF frequency from VHF to X-band in ground-sited radar. These results indicate that the frequency dependence of ground clutter strength depends upon terrain type and can vary, for example, from a strongly decreasing function of frequency in forest to a strongly increasing function of frequency in farmland. Five major terrain categories are defined that encompass this dependence, namely, urban, mountains, forest, farmland, and desert. Within each terrain category, results are also shown to be dependent upon relief or roughness of the terrain and upon the depression angle at which the terrain is illuminated. The depression angle dependence is important, even for the very low angles (typically within a degree of grazing incidence) and small (typical fractional) variations in angle that occur in ground-sited radar. This report presents specific clutter strength results at each of five frequencies (VHF, UHF, L-, S-, and X-band) from each of the 42 sites at which measurements were conducted. The report then combines results from similar sites to obtain the general dependence of clutter strength versus frequency for each terrain category. clutter strengths are described in terms of moments (including the mean) and percentile levels (including the median) in measured clutter amplitude distributions resulting from cell-by-cell spatial variation over a selected large kilometer-sized macroregion of terrain at each site called the repeat sector. Measurements over the repeat sector at each site were repeated a number of times to increase the reliability of the results.
This report determines how ground clutter strength varies with RF frequency from VHF to X-band in ground-sited radar. This determination is accomplished by providing extensive empirical results from multifrequency clutter measurements conducted at 42 different sites widely dispersed over the North American continent. These results indicate that the frequency dependence of ground clutter strength depends upon terrain type and can vary, for example, from a strongly decreasing function of frequency in forest to a strongly increasing function of frequency in farmland. Five major terrain categories are defined that encompass this dependence, namely, urban, mountains, forest, farmland, and desert. Within each terrain category, results are also shown to be dependent upon the relief or roughness of the terrain and upon the depression angle at which the terrain is illuminated. The depression angle dependence is important, even for the very low angles (typically within a degree of grazing incidence) and small (typically fractional) variations in angle that occur in ground-sited radar. This report presents specific clutter strength results at each of five frequencies (VHF, UHF, L-, S-, and X-band) from each of the 42 sites at which measurements were conducted. The report then combines results from similar sites to obtain the general dependence of clutter strength versus frequency for each terrain category. Clutter strengths are described in terms of moments (including the mean) and percentile levels (including the median) in measured clutter amplitude distributions resulting from cell-by-cell spatial variation over a selected large kilometer-sized macroregion of terrain at each site called the repeat sector.
This report determines how ground clutter strength varies with RF frequency from VHF to X-Band in ground sited radar. This determination is accomplished by providing extensive empirical results from multifrequency clutter measurements conducted at 42 different sites widely dispersed over the North American continent. These results indicate that the frequency dependence of ground clutter strength depends upon terrain type and can vary, for example, from a strongly decreasing function of frequence in forest to a strongly increasing function of frequency in farmland. Five major terrain categories are defined that encompass this dependence, namely, urban, mountain, forest, farmland and desert. Within each terrain category results are also shown to be dependent upon the relief or roughness of the terrain and upon the depression angle at which the terrain is illuminated. The depression angle dependence is important even for the very low angles and small variations in angle that occur in ground-sited radar. This report presents specific clutter strength results at each of five frequencies (VHF, UHF, L-, S- and X-band) from each of 42 sites at which measurements were conducted. The report then combines results from similar sites to obtain the general dependence of clutter strength versus frequency for each terrain category.
At MIT Lincoln Laboratory, we have collected a large multifrequency data base of radar ground clutter measurements from many sites. We employ our clutter data to develop clutter models. Of particular interest to us is the site-specific prediction of PPI ground clutter maps for ground-sited radars, that is, in simulating the spatial variation of ground clutter. This paper describes our measurements, and presents a statistical clutter model for spatial amplitude statistics based on depression angle, terrain type, RF frequency, and radar resolution.