300 research outputs found
Fractional Focusing and the Chirp Scaling Algorithm With Real Synthetic Aperture Radar Data
abstract: For synthetic aperture radar (SAR) image formation processing, the chirp scaling algorithm (CSA) has gained considerable attention mainly because of its excellent target focusing ability, optimized processing steps, and ease of implementation. In particular, unlike the range Doppler and range migration algorithms, the CSA is easy to implement since it does not require interpolation, and it can be used on both stripmap and spotlight SAR systems. Another transform that can be used to enhance the processing of SAR image formation is the fractional Fourier transform (FRFT). This transform has been recently introduced to the signal processing community, and it has shown many promising applications in the realm of SAR signal processing, specifically because of its close association to the Wigner distribution and ambiguity function. The objective of this work is to improve the application of the FRFT in order to enhance the implementation of the CSA for SAR processing. This will be achieved by processing real phase-history data from the RADARSAT-1 satellite, a multi-mode SAR platform operating in the C-band, providing imagery with resolution between 8 and 100 meters at incidence angles of 10 through 59 degrees. The phase-history data will be processed into imagery using the conventional chirp scaling algorithm. The results will then be compared using a new implementation of the CSA based on the use of the FRFT, combined with traditional SAR focusing techniques, to enhance the algorithm's focusing ability, thereby increasing the peak-to-sidelobe ratio of the focused targets. The FRFT can also be used to provide focusing enhancements at extended ranges.Dissertation/ThesisM.S. Electrical Engineering 201
Reduction of Vibration-Induced Artifacts in Synthetic Aperture Radar Imagery
Target vibrations introduce nonstationary phase modulation, which is termed the micro-Doppler effect, into returned synthetic aperture radar (SAR) signals. This causes artifacts, or ghost targets, which appear near vibrating targets in reconstructed SAR images. Recently, a vibration estimation method based on the discrete fractional Fourier transform (DFrFT) has been developed. This method is capable of estimating the instantaneous vibration accelerations and vibration frequencies. In this paper, a deghosting method for vibrating targets in SAR images is proposed. For single-component vibrations, this method first exploits the estimation results provided by the DFrFT-based vibration estimation method to reconstruct the instantaneous vibration displacements. A reference signal, whose phase is modulated by the estimated vibration displacements, is then synthesized to compensate for the vibration-induced phase modulation in returned SAR signals before forming the SAR image. The performance of the proposed method with respect to the signal-to-noise and signalto-clutter ratios is analyzed using simulations. Experimental results using the Lynx SAR system show a substantial reduction in ghosting caused by a 1.5-cm 0.8-Hz target vibration in a true SAR image
FMCW rail-mounted SAR: Porting spotlight SAR imaging from MATLAB to FPGA
In this work, a low-cost laptop-based radar platform derived from the MIT open courseware has been implemented. It can perform ranging, Doppler measurement and SAR imaging using MATLAB as the processor. In this work, porting the signal processing algorithms onto a FPGA platform will be addressed as well as differences between results obtained using MATLAB and those obtained using the FPGA platform. The target FPGA platforms were a Virtex6 DSP kit and Spartan3A starter kit, the latter was also low-cost to further reduce the cost for students to access radar technology
ΠΡΠΎΡΡΠΎΠΉ Π°Π»Π³ΠΎΡΠΈΡΠΌ ΠΊΠΎΠΌΠΏΠ΅Π½ΡΠ°ΡΠΈΠΈ ΠΌΠΈΠ³ΡΠ°ΡΠΈΠΉ ΡΠ²Π΅ΡΡΡΠΈΡ ΡΡ ΡΠΎΡΠ΅ΠΊ ΠΏΠΎ Π΄Π°Π»ΡΠ½ΠΎΡΡΠΈ Π΄Π»Ρ ΡΠ΅ΠΆΠΈΠΌΠ° Π±ΠΎΠΊΠΎΠ²ΠΎΠ³ΠΎ ΠΎΠ±Π·ΠΎΡΠ° Π Π‘Π (Π°Π½Π³Π».)
Introduction.Β Range Cell Migration (RCM) is a source of image blurring in synthetic aperture radars (SAR). There are two groups of signal processing algorithms used to compensate for migration effects. The first group includes algorithms that recalculate the SAR signal from the "alongβtrack range β slant range" coordinate system into the "along-track rangeΒ βΒ cross-track range"Β coordinates using the method of interpolation. The disadvantage of these algorithms is their considerable computational cost. Algorithms of the second group do not rely on interpolation thus being more attractive in terms of practical application.Aim. To synthesize a simple algorithm for compensating for RCM without using interpolation.Materials and methods. The synthesis was performed using a simplified version of the Chirp Scaling algorithm.Results.Β A simple algorithm, which presents a modification of the Keystone Transform algorithm, was synthesized. The synthesized algorithm based on Fast Fourier Transforms and the Hadamard matrix products does not require interpolation.Conclusion. A verification of the algorithm quality via mathematical simulation confirmed its high efficiency. Implementation of the algorithm permits the number of computational operations to be reduced. The final radar imageΒ produced using the proposed algorithm is built in the true Cartesian coordinates. The algorithm can be applied for SAR imaging of moving targets. The conducted analysis showed that the algorithm yields Β theΒ image of a moving target provided that the coherent processing interval is sufficiently large. The image lies along a line, which angle of inclination is proportional to the projection of the target relative velocity on the line-of-sight. Estimation of the image parameters permits the target movement parameters to be determined.ΠΠ²Π΅Π΄Π΅Π½ΠΈΠ΅. ΠΠΈΠ³ΡΠ°ΡΠΈΠΈ ΡΠ²Π΅ΡΡΡΠΈΡ
ΡΡ ΡΠΎΡΠ΅ΠΊ ΠΏΠΎ Π΄Π°Π»ΡΠ½ΠΎΡΡΠΈ ΡΠ²Π»ΡΡΡΡΡ ΠΈΡΡΠΎΡΠ½ΠΈΠΊΠΎΠΌ ΡΠ°ΡΡΠΎΠΊΡΡΠΈΡΠΎΠ²ΠΊΠΈ ΡΠ°Π΄ΠΈΠΎΠ»ΠΎΠΊΠ°ΡΠΈΠΎΠ½Π½ΡΡ
ΠΈΠ·ΠΎΠ±ΡΠ°ΠΆΠ΅Π½ΠΈΠΉ Π² ΡΠ°Π΄ΠΈΠΎΠ»ΠΎΠΊΠ°ΡΠΎΡΠ°Ρ
Ρ ΡΠΈΠ½ΡΠ΅Π·ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ Π°ΠΏΠ΅ΡΡΡΡΠΎΠΉ (Π Π‘Π). Π‘ΡΡΠ΅ΡΡΠ²ΡΠ΅Ρ Π΄Π²Π΅ Π³ΡΡΠΏΠΏΡ Π°Π»Π³ΠΎΡΠΈΡΠΌΠΎΠ² ΠΎΠ±ΡΠ°Π±ΠΎΡΠΊΠΈ ΡΠΈΠ³Π½Π°Π»ΠΎΠ² Π΄Π»Ρ ΠΊΠΎΠΌΠΏΠ΅Π½ΡΠ°ΡΠΈΠΈ ΠΌΠΈΠ³ΡΠ°ΡΠΈΠΉ. ΠΠ΅ΡΠ²Π°Ρ Π³ΡΡΠΏΠΏΠ° Π²ΠΊΠ»ΡΡΠ°Π΅Ρ Π°Π»Π³ΠΎΡΠΈΡΠΌΡ, Π² ΠΊΠΎΡΠΎΡΡΡ
Π½Π° ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΠΈ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠ² ΡΡΠ½ΠΊΡΠΈΠΎΠ½Π°Π»ΡΠ½ΠΎΠΉ ΠΈΠ½ΡΠ΅ΡΠΏΠΎΠ»ΡΡΠΈΠΈ ΠΎΡΡΡΠ΅ΡΡΠ²Π»ΡΠ΅ΡΡΡ ΠΏΠ΅ΡΠ΅ΡΡΠ΅Ρ ΠΏΡΠΈΠ½ΡΡΡΡ
ΡΠΈΠ³Π½Π°Π»ΠΎΠ² ΠΈΠ· ΡΠΈΡΡΠ΅ΠΌΡ ΠΊΠΎΠΎΡΠ΄ΠΈΠ½Π°Ρ "ΠΏΡΠΎΠ΄ΠΎΠ»ΡΠ½Π°Ρ Π΄Π°Π»ΡΠ½ΠΎΡΡΡ β Π½Π°ΠΊΠ»ΠΎΠ½Π½Π°Ρ Π΄Π°Π»ΡΠ½ΠΎΡΡΡ"Β Π² ΡΠΈΡΡΠ΅ΠΌΡ "ΠΏΡΠΎΠ΄ΠΎΠ»ΡΠ½Π°Ρ Π΄Π°Π»ΡΠ½ΠΎΡΡΡ β ΠΏΠΎΠΏΠ΅ΡΠ΅ΡΠ½Π°Ρ Π΄Π°Π»ΡΠ½ΠΎΡΡΡ". ΠΠ΅Π΄ΠΎΡΡΠ°ΡΠΊΠΎΠΌ Π°Π»Π³ΠΎΡΠΈΡΠΌΠΎΠ² Π΄Π°Π½Π½ΠΎΠΉ Π³ΡΡΠΏΠΏΡ ΡΠ²Π»ΡΠ΅ΡΡΡ ΠΈΡ
Π²ΡΡΠΎΠΊΠ°Ρ Π²ΡΡΠΈΡΠ»ΠΈΡΠ΅Π»ΡΠ½Π°Ρ ΡΠ»ΠΎΠΆΠ½ΠΎΡΡΡ. ΠΠ»Π³ΠΎΡΠΈΡΠΌΡ Π²ΡΠΎΡΠΎΠΉ Π³ΡΡΠΏΠΏΡ Π½Π΅ ΠΈΡΠΏΠΎΠ»ΡΠ·ΡΡΡ ΠΈΠ½ΡΠ΅ΡΠΏΠΎΠ»ΡΡΠΈΠΎΠ½Π½ΡΠ΅ ΠΌΠ΅ΡΠΎΠ΄Ρ ΠΈ ΡΠ²Π»ΡΡΡΡΡ ΠΏΠΎΡΡΠΎΠΌΡ Π±ΠΎΠ»Π΅Π΅ ΠΏΡΠΈΠ²Π»Π΅ΠΊΠ°ΡΠ΅Π»ΡΠ½ΡΠΌΠΈ Π΄Π»Ρ ΠΏΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ.Π¦Π΅Π»Ρ.Β Π‘ΠΈΠ½ΡΠ΅Π·ΠΈΡΠΎΠ²Π°ΡΡ ΠΏΡΠΎΡΡΠΎΠΉ Π°Π»Π³ΠΎΡΠΈΡΠΌ ΠΊΠΎΠΌΠΏΠ΅Π½ΡΠ°ΡΠΈΠΈ ΠΌΠΈΠ³ΡΠ°ΡΠΈΠΉ Π±Π΅Π· ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ ΡΡΠ½ΠΊΡΠΈΠΎΠ½Π°Π»ΡΠ½ΠΎΠΉ ΠΈΠ½ΡΠ΅ΡΠΏΠΎΠ»ΡΡΠΈΠΈ.ΠΠ°ΡΠ΅ΡΠΈΠ°Π»Ρ ΠΈ ΠΌΠ΅ΡΠΎΠ΄Ρ. Π‘ΠΈΠ½ΡΠ΅Π· Π°Π»Π³ΠΎΡΠΈΡΠΌΠ° ΠΎΡΡΡΠ΅ΡΡΠ²Π»Π΅Π½ Π½Π° ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΠΈ ΡΠΏΡΠΎΡΠ΅Π½Π½ΠΎΠΉ Π²Π΅ΡΡΠΈΠΈ Π°Π»Π³ΠΎΡΠΈΡΠΌΠ° ΠΠ§Π-ΡΠΈΠ»ΡΡΡΠ°ΡΠΈΠΈ (Chirp Scaling Algorithm).Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ. Π‘ΠΈΠ½ΡΠ΅Π·ΠΈΡΠΎΠ²Π°Π½ ΠΏΡΠΎΡΡΠΎΠΉ Π°Π»Π³ΠΎΡΠΈΡΠΌ, ΡΠ²Π»ΡΡΡΠΈΠΉΡΡ ΠΌΠΎΠ΄ΠΈΡΠΈΠΊΠ°ΡΠΈΠ΅ΠΉ Π°Π»Π³ΠΎΡΠΈΡΠΌΠ° "Π·Π°ΠΌΠΊΠΎΠ²ΠΎΠ³ΠΎ ΠΊΠ°ΠΌΠ½Ρ".ΠΠ»Π³ΠΎΡΠΈΡΠΌ ΠΎΡΠ½ΠΎΠ²Π°Π½ Π½Π° ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠΈ Π±ΡΡΡΡΡΡ
ΠΏΡΠ΅ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΠΉ Π€ΡΡΡΠ΅ ΠΈ ΠΏΠΎΡΠ»Π΅ΠΌΠ΅Π½ΡΠ½ΡΡ
ΠΌΠ°ΡΡΠΈΡΠ½ΡΡ
ΡΠΌΠ½ΠΎΠΆΠ΅Π½ΠΈΠΉ. Π Π°Π»Π³ΠΎΡΠΈΡΠΌΠ΅ Π½Π΅ ΠΏΡΠΈΠΌΠ΅Π½ΡΡΡΡΡ ΠΌΠ΅ΡΠΎΠ΄Ρ ΠΈΠ½ΡΠ΅ΡΠΏΠΎΠ»ΡΡΠΈΠΈ.ΠΠ°ΠΊΠ»ΡΡΠ΅Π½ΠΈΠ΅. ΠΡΠΎΠ²Π΅ΡΠΊΠ° ΠΊΠ°ΡΠ΅ΡΡΠ²Π° Π°Π»Π³ΠΎΡΠΈΡΠΌΠ° Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΌΠ°ΡΠ΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΠΎΠ΄ΡΠ²Π΅ΡΠ΄ΠΈΠ»Π° Π΅Π³ΠΎ Π²ΡΡΠΎΠΊΡΡ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ. ΠΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ Π°Π»Π³ΠΎΡΠΈΡΠΌΠ° ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΡΠΌΠ΅Π½ΡΡΠΈΡΡ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²ΠΎ Π²ΡΡΠΈΡΠ»ΠΈΡΠ΅Π»ΡΠ½ΡΡ
ΠΎΠΏΠ΅ΡΠ°ΡΠΈΠΉ.Π€ΠΈΠ½Π°Π»ΡΠ½ΠΎΠ΅ ΡΠ°Π΄ΠΈΠΎΠ»ΠΎΠΊΠ°ΡΠΈΠΎΠ½Π½ΠΎΠ΅ ΠΈΠ·ΠΎΠ±ΡΠ°ΠΆΠ΅Π½ΠΈΠ΅, ΠΏΠΎΠ»ΡΡΠ°Π΅ΠΌΠΎΠ΅ Ρ ΠΏΠΎΠΌΠΎΡΡΡ Π°Π»Π³ΠΎΡΠΈΡΠΌΠ°, ΡΡΡΠΎΠΈΡΡΡ Π²Β ΠΈΡΡΠΈΠ½Π½ΠΎΠΉ Π΄Π΅ΠΊΠ°ΡΡΠΎΠ²ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΠ΅ ΠΊΠΎΠΎΡΠ΄ΠΈΠ½Π°Ρ. ΠΠ»Π³ΠΎΡΠΈΡΠΌ ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ Π΄Π»Ρ ΠΏΠΎΡΡΡΠΎΠ΅Π½ΠΈΡ Π Π‘Π ΠΈΠ·ΠΎΠ±ΡΠ°ΠΆΠ΅Π½ΠΈΠΉ Π΄Π²ΠΈΠΆΡΡΠΈΡ
ΡΡ ΡΠ΅Π»Π΅ΠΉ. ΠΠ°Π½Π½ΡΠΉ Π² ΡΡΠ°ΡΡΠ΅ Π°Π½Π°Π»ΠΈΠ· ΠΏΠΎΠΊΠ°Π·Π°Π», ΡΡΠΎ Π°Π»Π³ΠΎΡΠΈΡΠΌ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΠΏΠΎΡΡΡΠΎΠΈΡΡ Ρ
ΠΎΡΠΎΡΠΎ ΡΡΠΎΠΊΡΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ΅ ΠΈΠ·ΠΎΠ±ΡΠ°ΠΆΠ΅Π½ΠΈΠ΅ Π΄Π²ΠΈΠΆΡΡΠ΅ΠΉΡΡ ΡΠ΅Π»ΠΈ, ΠΊΠΎΠ³Π΄Π° ΠΈΠ½ΡΠ΅ΡΠ²Π°Π» ΡΠΈΠ½ΡΠ΅Π·ΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π΄ΠΎΡΡΠ°ΡΠΎΡΠ½ΠΎ Π²Π΅Π»ΠΈΠΊ. ΠΠ·ΠΎΠ±ΡΠ°ΠΆΠ΅Π½ΠΈΠ΅ Π΄Π²ΠΈΠΆΡΡΠ΅ΠΉΡΡ ΡΠ΅Π»ΠΈ Π²ΡΡΡΡΠ°ΠΈΠ²Π°Π΅ΡΡΡ Π²Π΄ΠΎΠ»Ρ ΠΎΡΡΠ΅Π·ΠΊΠ° ΠΏΡΡΠΌΠΎΠΉ, ΡΠ³ΠΎΠ» Π½Π°ΠΊΠ»ΠΎΠ½Π° ΠΊΠΎΡΠΎΡΠΎΠΉ ΠΏΡΠΎΠΏΠΎΡΡΠΈΠΎΠ½Π°Π»Π΅Π½ ΠΏΡΠΎΠ΅ΠΊΡΠΈΠΈ ΠΎΡΠ½ΠΎΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠΊΠΎΡΠΎΡΡΠΈ ΡΠ΅Π»ΠΈ Π½Π° Π»ΠΈΠ½ΠΈΡ Π²ΠΈΠ·ΠΈΡΠΎΠ²Π°Π½ΠΈΡ. ΠΡΠ΅Π½ΠΊΠ° ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² ΠΈΠ·ΠΎΠ±ΡΠ°ΠΆΠ΅Π½ΠΈΡ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΠΈΡΡ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΡ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ ΡΠ΅Π»ΠΈ
Detection and classification of vibrating objects in SAR images
The vibratory response of buildings and machines contains key information that can be exploited to infer their operating conditions and to diagnose failures. Furthermore, since vibration signatures observed from the exterior surfaces of structures are intrinsically linked to the type of machinery operating inside of them, the ability to monitor vibrations remotely can enable the detection and identification of the machinery.
This dissertation focuses on developing novel techniques for the detection and M-ary classification of vibrating objects in SAR images. The work performed in this dissertation is conducted around three central claims. First, the non-linear transformation that the micro-Doppler return of a vibrating object suffers through SAR sensing does not destroy its information. Second, the instantaneous frequency (IF) of the SAR signal has sufficient information to characterize vibrating objects. Third, it is possible to develop a detection model that encompasses multiple scenarios including both mono-component and multi-component vibrating objects immersed in noise and clutter.
In order to cement these claims, two different detection and classification methodologies are investigated. The first methodology is data-driven and utilizes features extracted with the help of the discrete fractional Fourier transform (DFRFT) to feed machine-learning algorithms (MLAs). Specifically, the DFRFT is applied to the IF of the slow-time SAR data, which is reconstructed using techniques of time-frequency analysis. The second methodology is model-based and employs a probabilistic model of the SAR slow-time signal, the Karhunen-Loève transform (KLT), and a likelihood-based decision function. The performance of the two proposed methodologies is characterized using simulated data as well as real SAR data. The suitability of SAR for sensing vibrations is demonstrated by showing that the separability of different classes of vibrating objects is preserved even after non-linear SAR processing
Finally, the proposed algorithms are studied when the range-compressed phase-history data is contaminated with noise and clutter. The results show that the proposed methodologies yields reliable results for signal-to-noise ratios (SNRs) and signal-to-clutter ratios (SCRs) greater than -5 dB. This requirement is relaxed to SNRs and SCRs greater than -10 dB when the range-compressed phase-history data is pre-processed with the Hankel rank reduction (HRR) clutter-suppression technique
A Large Along-Track Baseline Approach for Ground Moving Target Indication Using TanDEM-X
In the paper a new method for ground moving target indication (GMTI) using two satellites (i.e. the TerraSAR-X and the TanDEM-X satellite) together is presented. The along-track baseline between the satellites is chosen to be in the order of several kilometres, so that each satellite observes the same moving vehicles at different times in the order of one to several seconds. The proposed method allows the estimation of the ground velocity of the moving targets as well as the estimation of the broadside positions without the need of complex bistatic processing techniques
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