An Inverse Synthetic Aperture Radar Azimuth Calibration Method

Abstract

The invention provides a retrosynthetic aperture radar azimuth calibration method which comprises the steps of carrying out range compression and translation compensation on imaging data, carrying out Keystone transformation correction linear range walking on a self-focused signal, determining medians of effective rotational speeds, a search interval and search point number, carrying out secondary phase term compensation on a signal after keystone transformation with each effective rotational speed to be estimated, carrying out azimuth imaging and obtaining an image entropy, after traversing all the effective rotational speeds to be estimated, searching the minimum image entropy, and taking the effective rotational speed corresponding to the minimum image entropy as the estimated effective rotational speed. After obtaining the estimated effective rotational speed, the search is carried out in a smaller interval near the value, the whole process is iterated for 3-4 times, and very high estimated accuracy can be achieved.

Description

technical field [0001] The invention relates to the field of radar imaging, in particular to an inverse synthetic aperture radar azimuth calibration method. Background technique [0002] Inverse Synthetic Aperture Radar (ISAR), as an all-day and all-weather long-range high-resolution sensor, has important application value in moving target imaging and target recognition. In automatic target recognition systems based on ISAR imaging, it is preferable to obtain the scale of the target. The scale factor in the distance direction is given by , where c is the speed of light and B is the bandwidth of the signal. The azimuth scale factor is given by determined, where λ is the wavelength of the transmitted signal, and Ω eff is the effective rotational speed, and T is the imaging accumulation time. [0003] In general, Ω eff If it is not known in advance, then the angle at which the object will turn during imaging is also not available. So far, there are about 4 types of ISA...

AI Technical Summary

Problems solved by technology

The first type uses narrow-band radar to obtain the change of the rotation angle of the moving target from the tracking data. This method can only approximate the change of the rotation angle caused by the change of the target relative to the radar line of sight, but is powerless for the change of the rotation angle caused by the rotation of the target itself, and For the complex motion of the target, the estimation error is often large, and even the correct estimation cannot be performed.

The second type of method uses the isolated point tracking method, which uses the third isolated scattering point on the tracking target (the first two points are used for translation and rotation compensation), and then obtains the rotation angle information; but it is difficult to find a very good isolated point in practice Scattering points, so it is rarely used in actual situations

However, this method does not consider the compensation of the quadratic phase term caused by the rotation speed, and the quadratic phase term will broaden the imaged azimuth image, especially at the edge of the target.

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