Two-dimensional non-linear frequency conversion and modulation method for SAR imaging of geosynchronous orbit

A geosynchronous orbit, non-linear technology, applied in the direction of using re-radiation, radio wave measurement system, radio wave reflection/re-radiation, etc., can solve the constraints of imaging scenes and imaging resolution, ignore the azimuth and space variability of imaging parameters, etc. question

Active Publication Date: 2014-06-04
BEIJING INSTITUTE OF TECHNOLOGYGY
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Problems solved by technology

In the traditional GEO SAR imaging algorithm, the nonlinear frequency modulation (NCS) algorithm is a relatively accurate imaging algorithm, but because the azimuth and space variability of GEO SAR imaging parameters are ignored, the imaging scene and imaging resolution are restricted.

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  • Two-dimensional non-linear frequency conversion and modulation method for SAR imaging of geosynchronous orbit
  • Two-dimensional non-linear frequency conversion and modulation method for SAR imaging of geosynchronous orbit
  • Two-dimensional non-linear frequency conversion and modulation method for SAR imaging of geosynchronous orbit

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[0058] The present invention will be described in detail below with reference to the accompanying drawings and examples.

[0059] The present invention provides a two-dimensional non-linear variable frequency modulation method for geosynchronous orbit SAR imaging. The present invention first establishes a GEO SAR space-variable model, in which the focus parameter in the SAR imaging process, that is, the slant distance of the radar, is considered The quadratic changes of the second-order coefficients in the range and azimuth directions in the historical 4th-order Taylor series expansion, and the linear changes of the third-order coefficients in the azimuth direction, and then according to the space-variant model, the range-wise NCS imaging processing and the azimuth NCS image processing, such as figure 1 As shown, it specifically includes the following steps:

[0060] Step 1. Establish GEO SAR space variation model

[0061] The working mode of SAR is a "Stop-and-go" mode. Le...

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Abstract

The invention discloses a two-dimensional non-linear frequency conversion and modulation method for SAR imaging of a geosynchronous orbit. By means of the two-dimensional non-linear frequency conversion and modulation method, imaging processing of GEO SAR large-scale scene echoes can be effectively completed. According to the two-dimensional non-linear frequency conversion and modulation method, firstly, a GEO SAR space variation model is established, wherein focusing parameters, namely secondary changes of the second-order coefficient in the distance direction and the azimuth direction during slope distance history 4-order Taylor series expansion of a radar and linear changes of the third-order coefficient in the azimuth direction, in the SAR imaging processing process are considered in the model; secondly, NCS imaging processing in the distance direction and NCS imaging processing in the azimuth direction are conducted according to the space variation model. Compared with the prior art, by means of the two-dimensional non-linear frequency conversion and modulation method, imaging processing of the GEO SAR large-scale scene echoes can be effectively completed, phase errors, caused by two-dimensional space variation of the parameters, in the azimuth direction are eliminated, accurate focusing in the azimuth direction can be completed, and imaging of the GEO SAR large-scale scene (400 km * 400 km) can be realized.

Description

technical field [0001] The invention relates to the technical field of synthetic aperture radar imaging, in particular to a two-dimensional non-linear variable frequency modulation method for geosynchronous orbit SAR imaging. Background technique [0002] Geosynchronous Orbit Synthetic Aperture Radar (GEO SAR) is a Synthetic Aperture Radar (SAR) system operating on a geosynchronous orbit satellite at an altitude of 36,000km above the ground. Since GEO SAR can cover an area of ​​more than 1000 km, and the revisit cycle of key areas can be less than 1 day, GEO SAR has great practical value in land detection, soil moisture detection, atmospheric water vapor mapping, and surface deformation detection. [0003] Due to the high orbital height of GEO SAR, the eccentricity is not zero, the satellite speed is small, the synthetic aperture time is long, and the observation range is large. image processing algorithm. Among the traditional GEO SAR imaging algorithms, the nonlinear fre...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01S13/90
CPCG01S13/904G01S13/9004G01S13/9058
Inventor 丁泽刚曾涛李延倪崇刘大成佟川
Owner BEIJING INSTITUTE OF TECHNOLOGYGY
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