Wideband radar can obtain much target information due to its high-range resolution. Because its size is smaller than the resolution of conventional radar, for an airplane, it can be regarded as a point. However, for wideband radar with a bandwidth of several hundred megahertz, the range resolution is less than a meter, and airplane echoes of one impulse form a high-resolution range profile (HRRP), which includes the shape information of a target that can be used for automatic target recognition (ATR). A range profile can be divided into many range resolution cells, each of which still contains the echoes of many scatterers. The complex amplitude of one range cell echo can be regarded as the sum of these echoes. A small aspect of change will lead to a big change of the complex amplitude, since, although the variation of the range of each scatterer to radar is very small, it is still large enough compared to the small wavelength and may cause a big phase change. Hence, the range profiles are very sensitive to the aspect angle, which makes the ATR based on HRRPs a well-known challenging problem. The properties of range profiles are investigated and a preprocessing scheme is presented to obtain stable range profiles for ATR.
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