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Inverse synthetic-aperture radar: Difference between revisions
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*'''Frequency and azimuth sampling errors:''' Incorrectly selected frequency or aspect deltas will result in [[aliased images]], creating spurious targets. The SIM program described earlier specifically monitors for aliening errors effectively eliminating this error source. | *'''Frequency and azimuth sampling errors:''' Incorrectly selected frequency or aspect deltas will result in [[aliased images]], creating spurious targets. The SIM program described earlier specifically monitors for aliening errors effectively eliminating this error source. | ||
*'''Antenna aberrations:''' Aberrations in the geometry result when the antenna phase center position is dependent upon the antenna aspect or RF frequency. This error source is normally controlled by using small, simple antennas over narrow frequency bands at long ranges. First order corrections to frequency dispersive antennas such as log periodic can be handled by phase correcting the received signal. Full correction of the aberrations can be accomplished by a direct integration of the ISAR transform using the aberrated geometry. | *'''Antenna aberrations:''' Aberrations in the geometry result when the antenna phase center position is dependent upon the antenna aspect or RF frequency. This error source is normally controlled by using small, simple antennas over narrow frequency bands at long ranges. First order corrections to frequency dispersive antennas such as log periodic can be handled by phase correcting the received signal. Full correction of the aberrations can be accomplished by a direct integration of the ISAR transform using the aberrated geometry. | ||
*'''Target dispersion:''' Dispersive targets have a non-minimum phase response, appearing to shift in position with [[Radio Frequency|RF]] frequency. Examples of dispersive targets include RF absorbers in which the absorption depth is a function of frequency and various antenna in which the phase center position is frequency dependent. [[Continuous Wavelength|CW]] ISAR imaging or in some cases preprocessing prior to a FMCW ISAR transform | *'''Target dispersion:''' Dispersive targets have a non-minimum phase response, appearing to shift in position with [[Radio Frequency|RF]] frequency. Examples of dispersive targets include RF absorbers in which the absorption depth is a function of frequency and various antenna in which the phase center position is frequency dependent. [[Continuous Wavelength|CW]] ISAR imaging or in some cases preprocessing prior to a FMCW ISAR transform can eliminate dispersive defocusing of the target image. | ||
*'''Multipath:''' Multiple reflections can result in ISAR imaging distortions such as the classic ghost image trails from [[jet aircraft]] [[tail pipes]]. | *'''Multipath:''' Multiple reflections can result in ISAR imaging distortions such as the classic ghost image trails from [[jet aircraft]] [[tail pipes]]. | ||
Errors in the 2D planar Inverse ISAR transform include: | Errors in the 2D planar Inverse ISAR transform include: | ||