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Ultrahigh-resolution synthetic aperture radar (SAR) imaging method based on frequency-stepped system

A technology of ultra-high resolution and imaging method, which is applied in the field of ultra-high-resolution SAR imaging of the stepping frequency modulation system, which can solve the problem of large phase error, and achieve the effects of avoiding phase difference, improving focusing, and expanding the focus range of the scene.

Inactive Publication Date: 2013-03-06
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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Problems solved by technology

[0006] The purpose of the present invention is to overcome the problem that the phase error is too large under the condition of ultra-high resolution existing in the existing linear frequency modulation scaling algorithm, and to provide a high-precision and high-efficiency step frequency modulation system ultra-high resolution SAR imaging method

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  • Ultrahigh-resolution synthetic aperture radar (SAR) imaging method based on frequency-stepped system
  • Ultrahigh-resolution synthetic aperture radar (SAR) imaging method based on frequency-stepped system
  • Ultrahigh-resolution synthetic aperture radar (SAR) imaging method based on frequency-stepped system

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Embodiment Construction

[0017] The technical scheme of the present invention is described in detail below in conjunction with accompanying drawing:

[0018] Assuming that the stepping interval of the radar transmitting carrier frequency under the stepping frequency modulation system is , the number of steps is N, and the pulse length is , the FM slope is , the subbandwidth is The step frequency modulation signal, its time-frequency relationship is as attached figure 1 shown, where the pulse repetition time is .

[0019] Define the azimuth sampling rate , corresponding to the first sub-pulse signals, the target echo signal at any point in the scene is

[0020] , (1)

[0021] in

[0022] , ,

[0023] represents a fast-time variable, expressed by For the slow time variable centered, is the instantaneous distance from the antenna phase center to the point target, the carrier frequency The carrier frequency corresponding to the full bandwidth signal, the carrier fre...

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Abstract

The invention discloses an ultrahigh-resolution synthetic aperture radar (SAR) imaging method based on a frequency-stepped system. Under the condition of an ultrahigh resolution, a phase error can be increased when a linear frequency variable metric algorithm is used, and the direct processing on SAR echo data can cause the image focusing quality to dramatically decline. The method comprises the following steps: firstly, extracting frequency-stepped subpulse signals as sub-bandwidth data; then, respectively focusing based on the linear frequency variable metric algorithm; and finally, transforming the focused sub-bandwidth data into a two-dimension frequency domain, and splicing and imaging in the two-dimension frequency domain. Compared with the prior art, the method can effectively improve the focusing quality of the point target, and can simultaneously avoid the phase difference among subpulses in the pulse group in the bandwidth synthesis process.

Description

technical field [0001] The invention relates to an ultra-high resolution synthetic aperture radar (Synthetic aperture radar, SAR for short) imaging method, in particular to a step frequency modulation system ultra-high resolution SAR imaging method. Background technique [0002] Synthetic aperture radar (SAR) is a new radar system that uses signal processing technology to image ground scenes. It uses the relative motion of the radar and the target to coherent the target echo signals received at different positions. Processing, so as to obtain high azimuth resolution. As an all-time, all-weather two-dimensional high-resolution imaging radar system, SAR has a wide range of applications in military and civilian fields. Since the improvement of resolution is of great help to the improvement of target recognition and feature extraction, ultra-high resolution SAR imaging technology has become one of the research hotspots in the field of SAR in recent years. [0003] Existing SAR...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01S13/90G01S7/40
Inventor 王昕朱岱寅
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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