SISAR: shadow inverse synthetic aperture radiolocation

A main prerequisite for obtaining radio images and for identifying air objects (AO) in bistatic radar systems, when using the shadow or forward scattering radiolocation method, is the fact that the shadow component of the forward-scattered field of an object relates to its shadow aperture by a two-dimensional Fourier transform in the Fraunhofer zone, or two-dimensional Fresnel transform in approaching the Fresnel zone. Since during the movement of AO prolonged observation (some tens of seconds) is possible and also the sum of the target signal and the direct signal of the transmitter is present at the reception point, an interference signal can be characterized as a one-dimensional shadow radio hologram synthesized coherently in time, or a radio holographic signal (RHS). It is known that a large-size high azimuth resolution (along the path line) equivalent receiving aperture can be synthesized when an observation system or a target is moving. In accordance with the established terminology we deal with the mode of synthetic aperture radar (SAR) in the first case, and with the mode of inverse SAR, or ISAR in the second case. Thus, when the shadow radiolocation is used, the mode of interest to us can be described as the mode of shadow ISAR, or SISAR in abbreviated form.