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Spaceborne SAR self-focusing method based on SAC algorithmic

A self-focusing, space-borne technology, applied in the direction of radio wave reflection/re-radiation, using re-radiation, measurement devices, etc., can solve problems such as complexity and consumption of storage resources, so as to relieve storage pressure, improve accuracy, and realize real-time Effect of treatment

Active Publication Date: 2015-12-23
BEIJING INSTITUTE OF TECHNOLOGYGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the MD algorithm itself is more complex than the SAC algorithm, and the estimation accuracy is comparable to
When the traditional SAC algorithm is implemented, the Doppler frequency estimation value of each range unit is directly calculated, which will consume a large amount of storage resources

Method used

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  • Spaceborne SAR self-focusing method based on SAC algorithmic
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  • Spaceborne SAR self-focusing method based on SAC algorithmic

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0046] Embodiment 1, as figure 1 As shown, the system is realized based on field-programmable gate array FPGA and its external memory DDR3 and external register set. FPGA integrates dual-port memory DPRAM, internal memory SDRAM, Fourier calculation core FFTIP core, position calculation module, frequency shift Correlation module, Focus module, Mean module, Cull module and Fit module.

[0047] Among them, the external memory DDR3 receives the original echo data sent by the satellite.

[0048] The external register set receives satellite parameter data; satellite parameter data includes: pulse repetition frequency prf, Doppler bandwidth W dop , and the Doppler center f of each piece of azimuth data dc .

[0049] The position calculation module obtains the satellite parameter data from the external register group, and calculates according to the satellite parameter data to obtain the following calculation results: the spectrum shift center position P of each azimuth data cent ...

Embodiment 2

[0057] Embodiment 2, the implementation steps of this system are as figure 2 As shown, specifically:

[0058] Step 1. Spectrum shifting and calculation of center position and effective length.

[0059] The position calculation module reads satellite parameters (pulse repetition frequency prf, Doppler bandwidth W dop ), and the Doppler center f of each piece of azimuth data dc , to calculate the spectral shift center position P of each azimuth data cent and effective data length L eff . The specific calculation formula is as follows:

[0060] L eff =floor(W dop × R line / prf / 2)1)

[0061] a num =floor(f dc / prf)2)

[0062] f' dc = f dc -a num ×prf3)

[0063] P cent =floor(f dcamb × R line / prf)+14)

[0064] In the formula, floor is an upward rounding operation; R line is the number of distance units; a num is the Doppler central fuzzy number; f′ dc is the Doppler center after deblurring. Calculation results are stored in FPGA internal SDRAM. According ...

Embodiment 3

[0082] Result of the present invention can further illustrate by following experiment:

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Abstract

The invention discloses a spaceborne SAR self-focusing system based on a SAC algorithm, which adopts FPGA to finish and receives original back waves and satellite parameters through an external device; the FPGA comprises a position calculation module which calculates and obtains position information of each orientation data, and stores the position information into a DPRAM through an SDRAM; the DPRAM obtains and reads effective spectrum data and inputs the data into an FFT IP core to perform IFFT, and the result is stored in the SDRAM; a frequency shift related module estimates a Doppler frequency value according to the IFFT result and stores the result into the SDRAM; a focusing module performs sub-module dividing and calculates the Doppler estimation value of each sub-module and the position thereof, and stores the Doppler estimation value and the position in the DPRAM; a value elimination module performs first value elimination on the estimation value in the DPRAM; an averaging module performs solution of mean square difference on the estimation value in the DPRAM; a fitting module performs a one-time linear fitting on the estimation value in the DPRAM, the value-elimination module eliminates the deviation value and obtains a fitting coefficient after repeating three times; and the Doppler frequency estimation is performed according to the fitting coefficient. The system disclosed by the invention can saves the internal resources of the FPGA and perform real-time processing.

Description

technical field [0001] The invention belongs to the technical field of radar real-time imaging processing, and relates to a space-borne SAR self-focusing realization method based on a SAC algorithm. Background technique [0002] Synthetic Aperture Radar (SAR) imaging system is widely used in many fields such as military and address detection because of its all-day and all-weather characteristics. In the SAR imaging system, theoretically, the radar carrier is required to move in a straight line at a uniform speed relative to the area to be imaged. In practice, however, the motion of the carrier deviates from this ideal, and this deviation produces a constant velocity error that introduces a quadratic phase error in the radar return data. If this deviation is not corrected, the azimuth direction of the image will be defocused, and even imaging will not be possible in severe cases. This error correction method is called Doppler frequency estimation. [0003] The commonly use...

Claims

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Application Information

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IPC IPC(8): G01S13/90
CPCG01S13/904G01S13/9047G01S13/9019
Inventor 谢宜壮李炳沂刘小宁陈禾龙腾
Owner BEIJING INSTITUTE OF TECHNOLOGYGY