Range migration algorithm for airborne squint mode spotlight SAR imaging

Shin, Hwi-Beom; Lim, Jong-Tae

doi:10.1049/iet-rsn:20060080

Cited by 29 publications

(15 citation statements)

References 7 publications

(7 reference statements)

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“…As for missile-borne SAR, PRF is over 10000 Hz, the height in cruise stage about 15000-20000 m, and the nearest slant range larger than operational height in slant mode. Substituting height and PRF into Equation (13), the calculation result meets the requirement. For missile-borne SAR platform, it is feasible to obtain echoes with small range migration in large squint angle by using variable PRF method.…”

Section: The Applicable Condition Of Variable Prf Imaging Methodsmentioning

confidence: 89%

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A Variable PRF Imaging Method for High Squint Diving Sar

Xu¹,

Gao²,

Li³

2013

PIER

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Abstract-The high squint diving SAR is widely used to provide the information in advance. Large squint angle deduces the deeper coupling of range and azimuth of SAR echoes which makes SAR imaging more difficult. Especially, the large range migration of the deep couple heavily burdens the imaging processing time and storage units. The diving motion of platform worsens the situation. This paper proposes the varied azimuth sample frequency (Pulse Repeat Frequency, PRF) to implement the high squint diving SAR imaging. Based on the signal model of the diving squint SAR, it is analyzed that the range walk is the prominent component of range migration in the high squint SAR. The varied PRF imaging method dramatically decreases the range walk of echoes by shifting the beginning position of transmitted pulses and received echoes and the shift is implemented by the PRF variation. Then the range migration is decreased and the couple of range and azimuth of SAR echoes is reduced. The PRF variation law is deduced and the applicable condition of varied PRF is presented. The simulation results show that the variable PRF method is efficient to reduce range walk of echoes. Comparison to the traditional constant PRF, the novel variable PRF method for high squint needs less storage and less time expense, which is helpful to real time SAR imaging. The non-uniform FFT can be used for the azimuth compressing of the variable PRF SAR. It will simplify the implementation of the variable PRF SAR imaging.

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Section: The Applicable Condition Of Variable Prf Imaging Methodsmentioning

confidence: 89%

“…The wavenumber domain algorithm, also called as range migration algorithm, is one kind of accurate algorithm for high squint SAR imaging [4,[12][13][14]. The modified stolt mapping is introduced to enlarge the range extension and to update the Doppler parameters in [4].…”

Section: Introductionmentioning

confidence: 99%

A Variable PRF Imaging Method for High Squint Diving Sar

Xu¹,

Gao²,

Li³

2013

PIER

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“…The azimuth time delay of target must be t d , thus the coefficient of t d f a must be −2π. Here the coefficient of t d f a is set as − 2π α to keep consistence with that of NCSA [9]. The α is a constant and its selection is discussed in detail in [21,22].…”

Section: Azimuth Nonlinear Chirp Scaling Operationmentioning

confidence: 99%

“…The imaging algorithms for spotlight SAR include the polar format algorithm (PFA) [1,7,8], the range migration algorithm (RMA) [1,[9][10][11], the chirp scaling algorithm (CSA) [12], the two step focusing approach (TSFA) [13][14][15] and the frequency scaling algorithm (FSA) [16,17] and so on. In PFA, the echo signal is dechirped with a reference function whose reference range is the instantaneous range of the scene center, which can be viewed as dechirp operation both in the range direction and in the azimuth direction.…”

Section: Introductionmentioning

confidence: 99%

An Extended Frequency Scaling Algorithm for High Squint Spotlight Airborne Sar

Zuo¹,

Pi²,

Min³

2013

PIER

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Abstract-In high squint spotlight mode SAR, the coupling of the range and azimuth is very serious, which brings challenges to the imaging. In this paper, an extended frequency scaling algorithm is proposed, in which the range migration correction is divided into two steps. Firstly the range walk correction is implemented in 2D time domain. In the second step, the residual range migration is corrected by the frequency scaling and bulk shift operations. Though the second range compression does not consider the range space variance, the range compression is precise. In the azimuth compression, because of the range walk correction, the azimuth modulation frequency rate becomes dependent on the azimuth position. In order to equalize the azimuth modulation frequency rate, the azimuth nonlinear chirp scaling method is involved to remove the dependence. The simulation experiments verify the validity of the proposed algorithm. The comparison of the imaging quality among traditional frequency scaling algorithm, nonlinear frequency scaling algorithm and the proposed method indicates the proposed method is more suitable for the high squint spotlight SAR.

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“…Some methods were introduced to convert the squint mode SAR data to improve the image quality [26,27]. The method in [26] assumes that the squint mode SAR data was not reliable and converted the squint mode SAR data to that in broadside mode using a complicated mathematical procedure.…”

Section: Motion Compensation Due To Turbulence and Problem In Squint mentioning

confidence: 99%

Motion Compensation for Squint Mode Spotlight Sar Imaging Using Efficient 2d Interpolation

Park¹,

Park²,

Kim³

2012

PIER

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Abstract-In the squint mode airborne spotlight synthetic aperture radar system using the range migration algorithm (RMA), autofocus (AF) technique yields poor results due to the squint spreading of the point spread function (PSF) of a scatterer. Thus, two-dimensional (2D) interpolation is required to direct PSF blurring in cross-range direction, to improve the cross-range resolution ∆y and to remove the spatially-varying sidelobe. Because conventional 2D interpolation requires huge computation time and yields large computation errors, we propose an efficient 2D interpolation technique for squint-mode RMA composed of two 1D interpolations. Simulation results using the measured turbulence data show ∆y was improved considerably and PSF was successfully focused by the proposed method with a reduced computation time.

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Range migration algorithm for airborne squint mode spotlight SAR imaging

Cited by 29 publications

References 7 publications

A Variable PRF Imaging Method for High Squint Diving Sar

A Variable PRF Imaging Method for High Squint Diving Sar

An Extended Frequency Scaling Algorithm for High Squint Spotlight Airborne Sar

Motion Compensation for Squint Mode Spotlight Sar Imaging Using Efficient 2d Interpolation

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