Imaging method for implementing airborne radar refocusing in system short of high-precision motion compensating system

Abstract

The invention relates to a re-focusing and imaging method for an on-board radar without any hi-precision motion compensation system, which comprises two procedures: (1) SAR initial compound image creation based on de-gradient processing; (2) Doppler signal phase error is measured based on improved PGA arithmetic, and compound image re-focusing for phase compensation is carried out. The second procedure comprises the following steps: the compound images are input; the center of the target with the most intensive point goes through cyclic movement; a window is added; Fourier transformation is done for orientation; estimation is made on the phase error; the phase is corrected; inverse Fourier transformation is done to return the compound image area. The invention allows to get on-board L-SAR re-focused images with resolution of orientation obviously improved only by original signal data without any hi-accuracy on-board platform movement compensation system to provide the info on movement state of an airplane; and the higher the contrast in the images, the better the focusing effect will be. As the SAR wavelength of L wave section is longer and penetrating, the invention can play high role in military reconnaissance and monitoring any disaster in civil application.

Description

technical field [0001] The invention relates to a method for realizing airborne radar refocusing imaging without a high-precision motion compensation system, and belongs to the technical field of synthetic aperture radar (SAR) signal digital imaging processing. Background technique [0002] Synthetic aperture radar is a type of imaging radar. It is usually installed on moving platforms such as aircraft, spacecraft or satellites, and obtains image information of ground targets by receiving and processing the electromagnetic waves radiated by the radar itself to the ground. As a means of microwave active remote sensing, it has advantages that optical remote sensing methods do not have. First of all, it has all-weather and all-weather working ability so that it is not affected by light and cloud coverage; secondly, due to the coherent characteristics of radar signals, the specially designed synthetic aperture radar can extract the three-dimensional information of the ground, a...

AI Technical Summary

Problems solved by technology

On a high-speed moving platform, it is very difficult to achieve this target

For example, the wavelength used in the L-band is 22-23cm. For an aircraft flying at a speed above 150m / s, it is very difficult to obtain such accurate positioning information.

At present, my country has not established a complete high-precision global positioning and navigation system, and the inertial navigation accuracy inside the airborne platform cannot meet the requirements of radar.

This will inevitably lead to poor control of the phase history parameters of the airborne radar Doppler signal, resulting in unstable radar image quality, blurred defocus and reduced resolution

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