CN106019280A - FMCW SAR imaging method and FMCW SAR imaging device based on distance Doppler correction - Google Patents

FMCW SAR imaging method and FMCW SAR imaging device based on distance Doppler correction Download PDF

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CN106019280A
CN106019280A CN201610381013.7A CN201610381013A CN106019280A CN 106019280 A CN106019280 A CN 106019280A CN 201610381013 A CN201610381013 A CN 201610381013A CN 106019280 A CN106019280 A CN 106019280A
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echo
signal
distance
frequency shift
doppler frequency
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CN106019280B (en
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王辉
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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
    • 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
    • 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
    • G01S13/9011—SAR image acquisition techniques with frequency domain processing of the SAR signals in azimuth
    • 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
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4052—Means for monitoring or calibrating by simulation of echoes
    • G01S7/4056—Means for monitoring or calibrating by simulation of echoes specially adapted to FMCW

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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)
  • Signal Processing (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The invention discloses an FMCW SAR imaging method and an FMCW SAR imaging device based on distance Doppler correction. The FMCW SAR imaging method comprises the following steps: step 1, an echo signal is received, and a difference frequency echo signal is acquired after Dechirp processing; step 2, the distance orientation Fourier transform of the difference frequency echo signal is carried out to complete distance orientation compression; step 3, the distance migration and the distance Doppler frequency shift correction of the echo signal after the distance orientation compression are carried out; step 4, the direction orientation Fourier transform and the focusing processing of the corrected echo signal are carried out to acquire an SAR image. By adopting the technical scheme provided by the invention, imaging quality is improved.

Description

FMCW SAR formation method based on range Doppler correction and device
Technical field
The invention belongs to synthetic aperture radar image-forming technical field, particularly relate to a kind of based on range Doppler frequency drift compensation Ka frequency range FMCW SAR formation method.
Background technology
FMCW SAR is risen in 21 beginnings of the century, due to its volume is little, lightweight, resolution is high and low cost and in army Favor is enjoyed with civil area.Start various countries from 2000 and start the development of FMCW SAR system, wherein Germany the most one after another Fraunhofer high-frequency physical and Radar Technology institute have developed a set of millimeter wave high-resolution FMCW SAR in 2000 System, this radar is operated in Ka and W-waveband, and emission maximum signal bandwidth reaches 2GHz.2002, Germany's EADS defence was logical Communication system company have developed the MISAR of FMCW system.The weight of first generation MISAR system is less than 4 kilograms and is provided that The resolution of 0.5 meter * 0.5 meter, can be mounted on SUAV LUNA, simultaneously the MiSAR of second filial generation X wave band Also development was completed in 2005.
TU Delft Polytechnics successfully have developed Ka wave band FMCW SAR model machine in 2003, it is achieved that 0.3m × 0.3m imaging.Having developed second-generation system MiniSAR in 2005 cooperatively with TNO-FEL subsequently, this system is operated in X wave band, can realize band and beam bunching mode by phased array antenna, and possess ground moving object instruction function.
Traditional pulsed SAR fire pulse width is narrow, during impulse action between antenna phase center and target Distance approximation do not change, thus use " step one is stopped " it is assumed that think that the instantaneous oblique distance of target was determined by the slow time, And it is unrelated with apart from the fast time." step one is stopped " assumes it is the basis of current PRF formula SAR imaging theory research, enormously simplify Theory analysis to SAR imaging.
But traditional " step one is stopped " is assumed to be applied to FMCW SAR, can affect the focusing effect of target.
Summary of the invention
The problem that the present invention solves is that existing SAR imaging technique is applied to FMCW SAR can cause target imaging weak effect, For solving described problem, the present invention provides a kind of FMCW SAR formation method based on range Doppler frequency shift correction and device.
The FMCW SAR formation method based on range Doppler frequency shift correction that the present invention provides includes:
Step one, reception echo-signal, Dechirp obtains difference frequency echo-signal after processing；
Step 2, described difference frequency echo-signal is carried out distance to Fourier transformation, complete distance to compression；
Step 3, to complete distance to compression echo-signal carry out range migration correction and range Doppler frequency shift correction；
Step 4, to correction after echo-signal carry out orientation to Fourier change and focusing, obtain SAR image.
Further, described step 3 includes:
Further, also include, at distance frequency domain, echo-signal is carried out RVP correction.
The present invention also provides for realizing FMCW SAR imaging side based on range Doppler frequency shift correction provided by the present invention The device of method, including: Dechirp processing module, distance are to Fourier transformation module, range migration and range Doppler frequency displacement school Positive module, orientation change module to Fourier；Described Dechirp processing module receives echo-signal, and carries out Dechirp process Obtaining difference frequency echo-signal, difference frequency echo-signal is transformed to distance domain to Fourier transformation module by distance；Range migration and away from It is corrected from Doppler correction module territory echo-signal of adjusting the distance；Orientation changes module to Fourier and enters echo-signal Row fourier transform of azimuth, and focal imaging.
High-quality image can be obtained by scheme provided by the present invention.
Accompanying drawing explanation
Fig. 1 is the FMCW SAR image obtained by prior art；
The FMCW SAR image that Fig. 2 is obtained for the method provided by the embodiment of the present invention.
Detailed description of the invention
From background technology, traditional " step one is stopped " is assumed to be applied to FMCW SAR, and the focusing of target can be caused to imitate The poorest.Inventor studies for the problems referred to above, it is believed that " step one is stopped " is assumed not to be suitable for FMCW SAR, and reason is radar All launching signal in whole frequency sweep cycle (pulse repetition period), its signal dutyfactor has reached 100%, and carrier aircraft is launching letter The target instantaneous oblique distance change caused of moving continuously during number is generally not capable of ignoring, and the change meeting of described target instantaneous oblique distance exists Distance, to producing additional Doppler frequency shift, correspondingly can cause the range migration of echo envelope, and then affect the focusing of target Effect.So needing to adjust the distance, migration and multiple spurs descriscent Doppler frequency shift are corrected.Inventor is after further research at this Invention provides a kind of FMCW SAR formation method based on range Doppler frequency shift correction.
Hereinafter, in conjunction with the accompanying drawings and embodiments spirit and substance of the present invention are further elaborated.
The FMCW SAR formation method based on range Doppler frequency shift correction that the present invention provides includes:
Step one, reception echo-signal, Dechirp obtains difference frequency echo-signal after processing.
Assume that radar is operated in the positive side-looking mode of strip-type, then to scene center point target, carrier aircraft position relative target Instantaneous oblique distance is
It is wherein nearest oblique distance during the inswept target of radar beam centrage, for carrier aircraft flight speed, for apart from the fast time, for side The position slow time.Different from pulsed SAR (instantaneous oblique distance ignores the impact apart from the fast time), the calculating of the instantaneous oblique distance of FMCW SAR Consider the impact apart from the fast time.
Difference frequency signal after Dechirp can be expressed as:
It is wherein imaginary unit, for the light velocity, for ripple Long, for signal chirp rate, for carrier aircraft flight speed, for target range, it is apart from the fast time for orientation to the time, for reference Oblique distance；
In formula, for frequency modulation removal distinctive residual video phase term (RVP, Residual Video Phase), it can affect orientation To Doppler, need to eliminate before pulse compression in orientation.Move continuously due to SAR platform and cause, i.e. carrier aircraft speed is drawn The phase term corresponding to Doppler frequency shift risen.
Step 2, described difference frequency echo-signal is carried out distance to Fourier transformation, echo-signal is transformed to distance frequency Territory, completes Range compress；
Step 3, to complete distance to compression echo-signal carry out range migration correction and range Doppler frequency shift correction；
Radar platform moves continuously in distance:
(4)
The ranging offset amount caused for Doppler frequency shift can be expressed as:
(5)
Wherein, PRI is frequency modulation cycle time, and B is transmitted signal bandwidth.
Wherein, R '=R+RdFor the target range measured；For target actual range；
In general, distance migratory motion correction is carried out at range-Dopler domain.Therefore, the distance migratory motion needs to be represented as only comprising change Amount R ' and fdForm.
R0=Rcos (Φ) (7)
Therefore range migration amount can be expressed as again:
Rm(R ', fd)=(1-cos (Φ)) (R '-Rd)+Rd (9)
(10)
The expression of migration of adjusting the distance with tradition is compared, the impact of extra item correspondence Doppler frequency shift.Platform motion causes many The impact that general Le frequency displacement causes can complete to compensate in range migration correction.
Interpolation method operand is big, construct at this range migration correction, Doppler frequency shift function as shown in Equation 11, directly Connecing is multiplied with echo-signal form with following formula can complete range migration correction and Doppler correction, and method is simple, processes Efficiency is high.
(11)
In a preferred embodiment of the invention, it is contemplated that RVP can change Doppler frequency, to echo-signal additional linearity error and Quadratic phase distortion, so carrying out RVP correction to echo-signal.
Owing to RVP item phase place is with spatial variations, be very difficult to remove in time domain, RVP at a warp factor of fast time domain, As long as different frequency is multiplied by the factor of and frequency dependence by distance to frequency domain, it is possible to remove completely, therefore, RVP correction Need to complete at distance frequency domain.
Structure RVP correction function:
Step 4, to correction after echo-signal carry out orientation to Fourier change and focusing, obtain SAR image.
Fig. 1 is the FMCW SAR image obtained by prior art；Fig. 2 is obtained for the method provided by the embodiment of the present invention The FMCW SAR image arrived.Utilize as can be seen from Figure 1 image that prior art obtains in orientation to distance to all there being difference Defocusing of degree, the image that the method provided by the embodiment of the present invention as seen from Figure 2 is obtained in orientation to distance to Focusing effect be obviously improved.
Although the present invention is open as above with preferred embodiment, but it is not for limiting the present invention, any this area Technical staff without departing from the spirit and scope of the present invention, may be by the method for the disclosure above and technology contents to this Bright technical scheme makes possible variation and amendment, therefore, every content without departing from technical solution of the present invention, according to the present invention Technical spirit any simple modification, equivalent variations and modification that above example is made, belong to technical solution of the present invention Protection domain.

Claims (6)

1. a FMCW SAR formation method based on range Doppler frequency shift correction, it is characterised in that including:
Step one, reception echo-signal, Dechirp obtains difference frequency echo-signal after processing；
Step 2, described difference frequency echo-signal is carried out distance to Fourier transformation, complete distance to compression；
Step 3, to complete distance to compression echo-signal carry out range migration and range Doppler frequency shift correction；
Step 4, to correction after echo-signal carry out orientation to Fourier change and focusing, obtain SAR image.
2. according to the FMCW SAR formation method based on range Doppler frequency shift correction described in claim 1, it is characterised in that Described step 3 includes:
Step 3.1, structure range migration and range Doppler frequency shift correction function
。
3. according to the FMCW SAR formation method based on range Doppler frequency shift correction described in claim 1, it is characterised in that Also include, at distance frequency domain, echo-signal is carried out RVP correction.
4. according to the FMCW SAR formation method based on range Doppler frequency shift correction described in claim 3, it is characterised in that RVP correction includes: structure RVP correction function；RVP correction function is multiplied with echo-signal.
5. according to the FMCW SAR formation method based on range Doppler frequency shift correction described in claim 1, it is characterised in that The difference frequency echo-signal that Dechirp obtains after processing is
It is wherein R target range, trFor orientation to the time.
6. realize the dress of FMCW SAR formation method based on range Doppler frequency shift correction provided in claim 1 to 5 Put, it is characterised in that including: Dechirp processing module, distance are to Fourier transformation module, range migration and range Doppler Frequency shift correction module, orientation change module to Fourier；Described Dechirp processing module receives echo-signal, and carries out Dechirp process obtains difference frequency echo-signal, and difference frequency echo-signal is transformed to distance domain to Fourier transformation module by distance；Away from It is corrected from migration and range Doppler frequency shift correction module territory echo-signal of adjusting the distance；Orientation changes module pair to Fourier Echo-signal carries out fourier transform of azimuth, and focal imaging.
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Publication number Priority date Publication date Assignee Title
CN106597437A (en) * 2016-11-23 2017-04-26 上海无线电设备研究所 High-frequency airborne FM continuous wave SAR motion compensation and imaging processing method
CN106597437B (en) * 2016-11-23 2019-10-18 上海无线电设备研究所 The airborne CW with frequency modulation SAR motion compensation of high frequency and image processing method
CN107741586A (en) * 2017-09-29 2018-02-27 王辉 Spaceborne Ka InSAR signal processing methods based on DBF TOPS weightings
CN108535719A (en) * 2017-12-29 2018-09-14 西安电子科技大学 CW with frequency modulation landing radar speed-measuring method based on the correction of Doppler frequency spectrum center of gravity
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CN108597234A (en) * 2018-05-10 2018-09-28 芜湖航飞科技股份有限公司 A kind of intelligent transportation detector based on high-resolution radar
CN114966694A (en) * 2022-07-29 2022-08-30 中国石油大学(华东) Range-doppler imaging algorithm suitable for FMCW signal
CN114966694B (en) * 2022-07-29 2022-10-28 中国石油大学(华东) Range-doppler imaging algorithm suitable for FMCW signal

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