6/19/2023 0 Comments Network radar gif![]() ![]() ![]() For instance a feature which extends far over the surface of a ship such as a mast will provide a high sinusoidal response which is clearly identifiable in a two dimensional image. In these applications the motion of the object due to wave action often plays a greater role than object rotation. ISAR is used in maritime surveillance for the classification of ships and other objects. The focusing is accomplished by applying a phase correction to the synthetic aperture. At this point the synthetic aperture is within the target nearfield region and requires focusing. This occurs when the synthetic aperture to the target range is less than required by the 2 D 2 λ is the required lateral extent of the target. The maximum rotation angle which can be processed by an unmodified Fourier transform is determined by the constraint that the aperture phase error across the synthesized aperture should vary by less than a specified (arbitrary) amount, for example 45 degrees. This Doppler history can not be processed directly by a Fourier transform because of the smeared Doppler frequency history resulting in the loss of cross range resolution. If the target is rotated through large angles, the Doppler frequency history of a scatterer becomes non-linear, following a sine wave trajectory. For small angles, an ISAR image is the 2-dimensional Fourier transform of the received signal as a function of frequency and target aspect angle. This operation is equivalent to (but the inverse of) the generation of a large synthetic-aperture phased-array antenna formed by the coherent summation of the receiver outputs for varying target / antenna geometries. The rotation will result in the generation of cross range dependent Doppler frequencies which can be sorted spatially by a Fourier transform. If the target rotates in azimuth at a constant rate through a 'small' angle, scatterers will approach or recede from the radar at a rate depending only on the cross range position- the distance normal to the radar line of sight with the origin at the target axis of rotation. ISAR images are often produced by rotating the target and processing the resultant Doppler histories of the scattering centers. Images of the target region produced by ISAR can be a useful tool in locating scattering regions on the target. In situations where other radars display only a single unidentifiable bright moving pixel, the ISAR image is often adequate to discriminate between various missiles, military aircraft, and civilian aircraft. ![]() ISAR radars have a significant role aboard maritime patrol aircraft to provide them with radar image of sufficient quality to allow it to be used for target recognition purposes. It is analogous to conventional SAR, except that ISAR technology uses the movement of the target rather than the emitter to create the synthetic aperture. Inverse synthetic-aperture radar ( ISAR) is a radar technique using radar imaging to generate a two-dimensional high resolution image of a target. JSTOR ( July 2013) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: "Inverse synthetic-aperture radar" – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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