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In this unique book, Billingsley solves the problem of radar land clutter by showing the reader how to design and predict the performance of radars that operate in situations where echoes from the earth's surface interfere with radar target echoes.
The performance of ground-based radars is affected by the spectral characteristics of ground clutter. Most signal processing algorithms designed to enhance detection performance are Doppler-frequency-sensitive, such as the moving target indicator filter, Doppler processor and coherent clutter map. This report gives the results of a comprehensive spectral analysis of low-angle ground clutter, using the MIT Lincoln Laboratory Phase I data and the DREO S-band clutter data. The report presents the spectral analysis of ground clutter for different bands of radar frequency; describes the data used in the spectral analysis, including both the conventional Fourier analysis and a super-resolution spectral analysis technique; gives a brief background on the maximum entropy spectral estimate; and describes the particular procedure designed to bring out the spectral characteristics of ground clutter from short time series.
Detailed knowledge of the temporal statistics of ground clutter is essential to determine the detection threshold settings so as to maximize the probability of target detection while maintaining an acceptable probability of false alarm. The performance of existing false alarm control schemes is often limited due to a lack of detailed knowledge of the ground clutter temporal statistics. In this study we analyze experimental data to characterize the temporal statistics of low-angle ground clutter in terms of the clutter's linear amplitude distribution. Effects of radar frequency, polarization, waveform resolution, land covers and wind speed on the statistics are examined. Results show that the Ricean distribution and its limiting case, the Rayleigh distribution, are appropriate models for ground clutter in steady-state wind conditions. This implies that the diffuse clutter components, which give rise to the random properties of ground clutter may be modeled as a complex Gaussian process. We found, however, that at any given time there is a fraction of the resolution cells with clutter data having nonstationary temporal statistics not well modelled by the Ricean or Rayleigh distribution. The frequency of occurrence of nonstationary clutter statistics depends on radar frequency, land cover and wind speed. Forested land cover represents the worst case scenario. Application of the results of this study to determine optimal detection threshold settings is discussed. Radar clutter; Phased array radar; S band; Canada. (edc).
This report describes millimeter wave ground based radar cross section measurements taken to support the SWOE JT&E program over two years. RCS measurements were made on selected ground clutter patches for one month and over another 43-day period at Camp Grayling, MI; and for 47 days at Yuma Proving Ground, AZ. Instruments collected data on meteorological conditions, solar flux, and soil moisture content. A wide range of atmospheric conditions was observed in Grayling over the measurement periods. The conditions in Yuma over the measurement period were relatively stable. In this report, we describe the variations in the ground based measured RCS of different clutter types over time and space for environmental conditions encountered during the three field tests. We have developed and will present an empirical model to describe these variations for the Yuma and Grayling II environments.
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.
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. 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.