Self-focusing preprocessing method based on short-time fractional order Fourier domain filter

Abstract

The invention relates to a self-focusing preprocessing method based on a short-time fractional order Fourier domain filter, which belongs to the field of synthetic aperture radar (SAR) signal processing. The method comprises the following steps of: (1) extracting a phase error signal of a single special showing point; (2) judging whether the phases of the phase error signal mainly are quadratic phase or not; (3) filtering noise in a transform domain: if the phases mainly are quadratic phases, using short-time fractional order Fourier domain filter; otherwise, using short-time Fourier domain filter; and (4) inversely transforming result time frequency to a time domain, estimating and compensating the phase error and realizing self-focusing preprocessing. The method effectively solves the problems of estimation and compensation of the phase error in a low-signal-to-noise ratio environment, especially the estimation and compensation of the quadratic phase error, and can obtain the main part of a phase error course and greatly improve the imaging quality after removing the phase error course from an original signal, thereby improving the signal-to-noise ratio of a special showing point signal.

Description

technical field [0001] The invention relates to a self-focusing method, in particular to a self-focusing preprocessing method, which belongs to the field of synthetic aperture radar (SAR) signal processing. Background technique [0002] SAR achieves two-dimensional high-resolution imaging through pulse compression in the range direction and synthetic aperture processing in the azimuth direction. It can operate all-day and all-weather, can image underground and underwater scenes, and can accurately monitor land subsidence (using interferometric SAR) It has been widely used in many military and civilian fields such as battlefield reconnaissance, precision guidance, target recognition, resource detection, terrain mapping, environmental protection and disaster monitoring. The imaging model of SAR is based on the assumption that the radar payload is flying smoothly. However, due to various random disturbances in reality, errors in the motion of the radar payload are inevitable. ...

AI Technical Summary

Problems solved by technology

The effect of frequency domain filtering depends on the degree of separation of signal and noise in the frequency domain: stationary signals occupy a narrow bandwidth in the frequency domain, and the signal and noise are highly separated, so the filtering effect is very good; but non-stationary signals may occupy a large frequency domain bandwidth, a lot of noise cannot be separated from it, so the filtering effect may be poor

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