CN105699947B - A kind of SAR image side lobe suppression method - Google Patents

A kind of SAR image side lobe suppression method Download PDF

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CN105699947B
CN105699947B CN201610050709.1A CN201610050709A CN105699947B CN 105699947 B CN105699947 B CN 105699947B CN 201610050709 A CN201610050709 A CN 201610050709A CN 105699947 B CN105699947 B CN 105699947B
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sar image
image
points
response
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CN105699947A (en
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闵锐
左峰
皮亦鸣
郝居博
曹宗杰
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University of Electronic Science and Technology of China
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/9004—SAR image acquisition techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/2813—Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/904—SAR modes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/904—SAR modes
    • G01S13/9088—Circular SAR [CSAR, C-SAR]

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  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The invention belongs to radar imaging technology fields, and in particular to a kind of SAR image side lobe suppression method.The present invention can be good at improving the accuracy rate of identification target using the comparison by original image and image after adding window.Meanwhile piecemeal is carried out to imaging region, different regions uses different reference standards, additionally it is possible to which impulse response caused by the factors such as good correction distance migration deforms.This to keep main lobe width constant while suppressed sidelobes is imitated.In addition, the entire implementation process in the present invention is all only related to some simple arithmetical operations, be not related to inverting, the complex calculations such as feature decomposition, thus the present invention realize it is also very simple.

Description

A kind of SAR image side lobe suppression method
Technical field
The present invention relates to radar imaging technology field, more particularly to a kind of synthetic aperture radar SAR (synthetic Aperture radar) image side lobe suppression method.
Background technology
Since the frequency domain support region of SAR imaging systems two dimension is limited so that the impulse response letter of synthetic aperture radar Number distance to be sinc functions in orientation, the excessively high master that can flood weak signal target of secondary lobe of strong target echo in image Valve.Particularly during SAR image interpretation and target interpretation, the SAR image of high secondary lobe will substantially reduce system to weak signal target Processing capacity, while strong target interpretation precision as secondary lobe interference and be affected.Therefore, secondary lobe is reduced for subtracting Few false-alarm and raising Testing of Feeble Signals ability are of great significance to.
More commonly used in Sidelobe Suppression is that window adding in frequency domain is carried out after matched filtering, processing and to the number in entire aperture Amplitude weighting is carried out according to fixed weighting function.Pulse pressure waveform after windowing process has relatively low secondary lobe, can meet practical It needs but makes main lobe broadening, amplitude reduction again simultaneously, seriously affected the quality of image.Consequently, it is desirable to find better secondary lobe Level suppression technology.
1974,Propose it is a kind of for improve synthetic aperture radio astronomy observation into figure quality, can disappear Except the method being had an impact due to space frequency cover is imperfect, by the Sidelobe Suppression improved by this method for SAR image. The main thought of this method is the response that position where finding out target replaces secondary lobe with the impulse response for blocking secondary lobe.It Main lobe width can be kept constant on the basis of secondary lobe is completely inhibited.But its shortcoming is it is also obvious that in many cases, and Only it cannot judge that the point whether there is target by the amplitude size of SAR echoes.The judgement of mistake can cause false target Appearance and the missing inspection of weak signal target.
Invention content
For above-mentioned there are problem or deficiency, the present invention provides a kind of SAR image side lobe suppression methods, effectively improve The appearance of false target and the missing inspection problem of weak signal target.
The SAR image side lobe suppression method, includes the following steps：
Areas imaging is divided into K region by step 1, is emulated by using actual parameter and same imaging mode Obtain response h of the point target Jing Guo normalized at each regional centerk(m, n) (k=1,2..., K, m=1,2..., M, n =1,2..., N), wherein M be SAR image orientation points, N be SAR image distance to points, it is carried out at adding window Reason meets with a response
Step 2 directly generates the point target echo response S (m, n) after ideal normalized according to actual parameter, and Its secondary lobe is blocked and leaves behind main lobe and is denoted as h (m, n)；
The method for intercepting main lobe is as follows：
Step 2-1：Localizer unit where taking S (m, n) amplitude maximum point, is denoted as Sa (n), is searched for from its maximum value to both sides All the points except this 2 points are all set to 0, the signal after setting to 0 are denoted as Sa by each first 0 value point in side1(n)；
Step 2-2：Impulse response S of the distance after secondary lobe is blocked is obtained as the following formularcut(m,n)
Wherein, Fast Fourier Transform (FFT) is done signal in FFT () expressions, and IFFT () expressions are done signal in inverse quick Fu Leaf transformation；
Step 2-3：Range cell where taking S (m, n) amplitude maximum point, is denoted as Sr (m), is searched for from its maximum value to both sides All the points except this 2 points are all set to 0, the signal after setting to 0 are denoted as Sr by each first 0 value point in side1(m)；
Step 2-4：Orientation is obtained as the following formula blocks the impulse response h (m, n) after secondary lobe
Step 3：Windowing process is carried out to SAR image Sr (m, n)
Wherein,For the SAR image after adding window, win (m, n) is the two-dimentional window function to be added；
Step 4：Compare two images Sri(m, n) andFind out be in two images maximum point andMiddle individualism and satisfactionMaximum point (m0,n0) where position, remember its be (mi, ni)；In SriThe product of the echo response and cycle step-length γ of the region is subtracted in (m, n)；If the point is The maximum point of middle individualism then enables γ=1, otherwise, enable γ=γ0, γ0For initial cycle step-length, 0<γ0<1；
Sri+1(m, n)=Sri(m,n)-γ*Sri(mi,ni)*hk(m-mi,n-ni) (4)
Srouti+1(m, n)=Srouti(m,n)+γ*Sri(m,n)*h(m-mi,n-ni) (5)
Wherein, hk(m-mi,n-ni) represent hk(m, n) moves to (mi,ni) response, Sri(m, n) represents the i-th (i= 0,1,2 ...) remaining part after secondary iteration, and Sr0(m, n)=Sr (m, n).Srouti(m, n) represents the suppression of ith iteration secondary lobe Result after system；
Identical operation is done i.e. to the image after adding window：
Wherein,Representing willIt moves toResponse,After representing adding window Remainder of the image after i iteration；
Step 5：The iterative operation in step 4 is repeated, until residual signal reaches noise level；So far, it is possible to obtain Image after Sidelobe Suppression；The condition whether judgement iteration terminates is as follows：
El<α*E0 (7)
Wherein, ElFor SrlThe energy of (m, n),α(0<α<1) it is the threshold values system of decision condition Number.
The present invention can be good at improving the accurate of identification target using the comparison by original image and image after adding window Rate.Meanwhile piecemeal is carried out to imaging region, different regions uses different reference standards, additionally it is possible to good correction distance Impulse response caused by the factors such as migration deforms.This to keep main lobe width constant while suppressed sidelobes is imitated.In addition, The entire implementation process of the present invention is all only related to some simple arithmetical operations, is not related to inverting, the complicated fortune such as feature decomposition It calculates, therefore the present invention realizes also very simply.
In conclusion the invention has the advantages that：Keep main lobe width constant while suppressed sidelobes is imitated；Know The accuracy rate of other target is high；It is simple that implementation process does not relate to complex calculation process.
Description of the drawings
Fig. 1 is the flow chart of SAR image side lobe suppression method of the present invention；
Fig. 2 is the point target imaging results of each region after piecemeal；
Imaging results after Fig. 3 piecemeals after each region point target adding window；
Fig. 4 is ideal point target imaging results；
Fig. 5 is the ideal point target imaging results blocked after secondary lobe；
Fig. 6 is to want pending SAR image；
Fig. 7 is the result to pending SAR image adding window；
Fig. 8 is the result after suppressed sidelobes.
Specific embodiment
The present invention is described further with embodiment below in conjunction with the accompanying drawings.
According to flow operations shown in preceding method, that is, Fig. 1, the specific setting of simulation parameter is as follows：Using circumference SAR into As pattern, the distance of distance by radar scene center is 10 meters, and the bandwidth for emitting signal is 30GHz, and the center carrier frequence of signal is 300GHz, the imaging algorithm of use is RD algorithms.
Fig. 2 and Fig. 3 is the result that step 1 is handled：Imaging region divide, each region center is obtained by emulation Result after the point target echo response and adding window at place.
Fig. 4 and Fig. 5 is the result that step 2 is handled.Wherein, Fig. 4 is ideal point target imaging results, and Fig. 5 is to block side Main lobe part after valve.
Fig. 6 is SAR image to be processed, as can be seen from the figure point target due to range migration compared to ideal Point target echo distorted, while can be seen that the upper right corner two points due to distance it is too near and inseparable.
Fig. 7 is Fig. 6 handled by step 3 after after adding window as a result, as can be seen from the figure two points in the upper right corner may be used To separate, but simultaneously it can also be seen that the secondary lobe of point target is all widened.
Fig. 8 is as a result, as can be seen from the figure secondary lobe is repressed while main lobe is not opened up after suppressed sidelobes of the present invention It is wide.Moreover, the distortion that echo is generated due to range migration has also obtained good correction.
In conclusion it can be seen that the effective of SAR image side lobe suppression method provided by the invention from the result of processing Property and helpfulness.

Claims (1)

1. a kind of SAR image side lobe suppression method, includes the following steps：
Areas imaging is divided into K region by step 1, emulates to obtain by using actual parameter and same imaging mode Response h of the point target Jing Guo normalized at each regional centerk(m, n), wherein k=1,2 ..., K, m=1,2 ..., M, n= 1st, 2 ..., N, M be SAR image orientation points, N be SAR image distance to points, windowing process is carried out to it and is rung It should
Step 2 directly generates the point target echo response S (m, n) after ideal normalized according to actual parameter, and by its Secondary lobe, which blocks, to be left behind main lobe and is denoted as h (m, n)；
The method for intercepting main lobe is as follows：
Step 2-1：Localizer unit where taking S (m, n) amplitude maximum point, is denoted as Sa (n), and each side is searched for from its maximum value to both sides All the points except this 2 points are all set to 0, the signal after setting to 0 are denoted as Sa by first 0 value point1(n)；
Step 2-2：Impulse response S of the distance after secondary lobe is blocked is obtained as the following formularcut(m,n)
Wherein, Fast Fourier Transform (FFT) is done signal in FFT () expressions, and IFFT () expressions are done signal inverse fast Fourier and become It changes；
Step 2-3：Range cell where taking S (m, n) amplitude maximum point, is denoted as Sr (m), and each side is searched for from its maximum value to both sides All the points except this 2 points are all set to 0, the signal after setting to 0 are denoted as Sr by first 0 value point1(m)；
Step 2-4：Orientation is obtained as the following formula blocks the impulse response h (m, n) after secondary lobe
Step 3：Windowing process is carried out to SAR image Sr (m, n)
Wherein,For the SAR image after adding window, win (m, n) is the two-dimentional window function to be added；
Step 4：Compare two images Sri(m, n) andFind out be in two images maximum point andMiddle individualism and satisfactionMaximum point (m0,n0) where position, remember that it is (mi,ni)；In SriThe product of the echo response and cycle step-length γ of the region is subtracted in (m, n)；If the point isThe maximum point of middle individualism then enables γ=1, otherwise, enable γ=γ0, γ0For initial cycle step-length, 0 ＜ γ0 ＜ 1；
Sri+1(m, n)=Sri(m,n)-γ*Sri(mi,ni)*hk(m-mi,n-ni) (4)
Srouti+1(m, n)=Srouti(m,n)+γ*Sri(m,n)*h(m-mi,n-ni) (5)
Wherein, hk(m-mi,n-ni) represent hk(m, n) moves to (mi,ni) response, Sri(m, n) is remained after representing ith iteration Remaining part, wherein i=0,1,2 ..., and Sr0(m, n)=Sr (m, n), SroutiAfter (m, n) represents ith iteration Sidelobe Suppression Result；
Identical operation is done i.e. to the image after adding window：
Wherein,Representing willMove to (mi,ni) response,Represent the image after adding window Remainder after i iteration；
Step 5：The iterative operation in step 4 is repeated, until residual signal reaches noise level；So far, it is possible to obtain secondary lobe Image after inhibition；The condition that judgement iteration terminates is as follows：
Ei＜ α * E0 (7)
Wherein, EiFor SriThe energy of (m, n),α is the threshold coefficient of decision condition, wherein 0 ＜ α ＜ 1.
CN201610050709.1A 2016-01-25 2016-01-25 A kind of SAR image side lobe suppression method Expired - Fee Related CN105699947B (en)

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CN108008381B (en) * 2017-06-09 2019-01-01 北京航空航天大学 A kind of target bearing side lobe suppression method and device based on angles of azimuth SAR image
CN107765225A (en) * 2017-10-27 2018-03-06 中国人民解放军国防科技大学 Sparse regularization SAR image sidelobe suppression method based on log measurement
CN111060879B (en) * 2019-11-22 2021-09-10 北京理工大学 Joint side lobe suppression method based on two-dimensional matched filtering result
CN110865344B (en) * 2019-11-22 2021-06-29 北京理工大学 Rapid side lobe suppression method under pulse Doppler radar system
CN110927720B (en) * 2019-11-27 2021-02-26 北京宏锐星通科技有限公司 SAR sidelobe countermeasure method

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