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Low-frequency synthetic aperture radar image comparison and cancellation radio frequency interference suppression method

A technology of synthetic aperture radar and image comparison, applied in the field of signal processing, to achieve the effect of strong robustness, simple structure, and robust RFI suppression performance

Active Publication Date: 2017-04-26
NAT UNIV OF DEFENSE TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved in the present invention is to provide a low-frequency synthetic aperture radar (SAR) image contrast destructive radio frequency interference (RFI) suppression method to solve the problem of time-varying RFI in low-frequency SAR imaging. Suppresses issues and improves image quality

Method used

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  • Low-frequency synthetic aperture radar image comparison and cancellation radio frequency interference suppression method

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Effect test

Embodiment 1

[0064] Embodiment 1: Processing the simulation data set A formed by adding the time-domain echoes of time-varying and non-time-varying RFI.

[0065] The first step is range spectrum equalization and SAR imaging based on radar time-frequency domain echoes. Specifically include:

[0066] Step 1.1: Calculate the mean magnitude spectrum

[0067] Take N consecutive time-domain echoes R i (t m ,t f ), where i=1,2,...N, perform Fourier transform on each time-domain echo along the distance time domain, and obtain N time-frequency domain echoes R i (t m , f r ), to obtain the average magnitude spectrum

[0068]

[0069] Step 1.2: Spectral equalization for RFI suppression

[0070] With each time-frequency domain echo R i (t m , f r ) multiplied by the reciprocal of the average amplitude spectrum within the signal bandwidth to suppress RFI for interference higher than the signal strength, and obtain the time-frequency domain echo R after spectrum equalization i '(t m , ...

Embodiment 2

[0099] Embodiment 2: Process the measured data

[0100] The specific process is similar to that of Embodiment 1, and will not be repeated here, only the processing results will be described.

[0101] Figure 8 The results of processing the measured data by spectral equalization RFI suppression method are given. There is time-varying RFI interference in the measured data. Figure 8 There is obvious clutter caused by residual RFI at the position indicated by the arrow in the upper right of the center, and there is a strong target in the circle at the lower left.

[0102] Figure 9 The results of processing the measured data by adaptive NLMS filtering RFI suppression method are given. Figure 9 There is basically no residual RFI interference indicated by the arrow in the upper right of the center, but the same strong target in the lower left circle is opposite Figure 8 Higher sidelobes appear along the distance direction.

[0103] Figure 10 The result of processing the m...

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Abstract

The invention discloses a low-frequency synthetic aperture radar image comparison and cancellation radio frequency interference suppression method. The method includes three steps: 1. conducting range spectrum and SAR imaging based on radar time-frequency domain echoes to obtain an image (I-bar <1>(t<m>,t<f>); 2. conducting intra-pulse RFI suppression and SAR imaging based on adaptive filtering to obtain an image (I-bar<2>(t<m>,t<f>); and 3. comparing the amplitude values of the pixel points of the image (I-bar <1>(t<m>,t<f>) and those of the image (I-bar<2>(t<m>,t<f>) point by point and removing residual RFI to obtain an image I<o> (t<m>, t<f>) which is the SAR image with the residual RFI suppressed by adopting the method of image comparison and cancellation. According to the invention, the method uses the spectrum balancing which can stabilize RFI suppression properties in combination with adaptive NLMS filtering, realizes complementary properties of the RFI suppression and obviates the need for registering the generated image. The method can conduct direct comparison on image domain point by point, removes the residual RFI, requires small operation, has strong real-timeness and is easy to be engineered.

Description

technical field [0001] The invention belongs to the technical field of signal processing, in particular to a low-frequency synthetic aperture radar image contrast destructive radio frequency interference suppression method. Background technique [0002] Low-frequency SAR (Synthetic Aperture Radar) refers to the SAR whose radar operating frequency is located in the VHF (Very High Frequency) / UHF (Ultra High Frequency) frequency band, because there are a large number of communication, broadcasting, and television signals in this frequency band source, the radar image will be affected by RFI (Radio Frequency Interference, radio frequency interference) with narrow-band characteristics, time-varying and space-varying. Experiments show that RFI will seriously affect the quality and subsequent application of SAR images. [0003] At present, the RFI suppression method used in low-frequency SAR is mainly to improve the SAR imaging quality, and to evaluate the suppression performance ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01S13/90
CPCG01S13/904G01S7/023G01S13/9004
Inventor 李悦丽黎向阳安道祥黄晓涛范崇祎刘晓聪
Owner NAT UNIV OF DEFENSE TECH
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