155 results on '"SAR processing"'
Search Results
2. Geochemical analysis of SAR backscattering (Sentinel-1) on global ocean oil spill cases.
- Author
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Neves de Souza Júnior, José Milton, Ferreira de Mendonça, Luís Felipe, da Silva Costa, Heverton, Costi, Juliana, Vasconcelos, Rodrigo Nogueira, Telles da Cunha Lima, André, João Siqueira Sant'anna, Sidnei, Marques Lopes, José, José Porsani, Milton, Vivas Garica Miranda, de José, and Alessandre Domingos Lentini, Carlos
- Subjects
ANALYTICAL geochemistry ,OIL spills ,MARINE pollution ,BACKSCATTERING ,HEAVY oil ,GRAVITY waves ,MINERAL oils - Abstract
The oil spill is one of the most impactful sources of marine pollution on the ocean surface, detected by the SAR sensors as dark areas, regions with low backscatter values. Due to the complex mixture of hydrophobic hydrocarbons, mineral oil spills change the water surface tension dampening the capillary gravity waves and provoking a specular reflection. In this work, we associated the geochemical oil characteristics, such as density, viscosity, API, and molecular composition with the backscatter values for each oil spill case. We identified the relationship between the oil weathering processes, with the changes in the backscattering values of ocean oil spills. The method designed zonal sections over the oil spills detected in the SAR images, to extract the backscatter values for each pixel along the section. The lowest backscatter average was observed by the heavy oil spill in the Corsica Island study (−29,99 dB). The highest level of weathering had the highest backscatter averages. Damping rates ranged between 4,12 and 7,07 dB and the backscatter values may be related to low oil layer thickness. Furthermore, low wind speeds may have reduced the contrast between water and oil spills, resulting in low damping ratios in all events. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. Geochemical analysis of SAR backscattering (Sentinel-1) on global ocean oil spill cases
- Author
-
José Milton Neves de Souza Júnior, Luís Felipe Ferreira de Mendonça, Heverton da Silva Costa, Juliana Costi, Rodrigo Nogueira Vasconcelos, André Telles da Cunha Lima, Sidnei João Siqueira Sant’anna, José Marques Lopes, Milton José Porsani, de José Vivas Garica Miranda, and Carlos Alessandre Domingos Lentini
- Subjects
Synthetic Aperture Radar (SAR) ,SAR processing ,oil spills ,radar backscatter ,normalized radar cross section ,damping ratio ,Oceanography ,GC1-1581 ,Geology ,QE1-996.5 - Abstract
ABSTRACT The oil spill is one of the most impactful sources of marine pollution on the ocean surface, detected by the SAR sensors as dark areas, regions with low backscatter values. Due to the complex mixture of hydrophobic hydrocarbons, mineral oil spills change the water surface tension dampening the capillary gravity waves and provoking a specular reflection. In this work, we associated the geochemical oil characteristics, such as density, viscosity, API, and molecular composition with the backscatter values for each oil spill case. We identified the relationship between the oil weathering processes, with the changes in the backscattering values of ocean oil spills. The method designed zonal sections over the oil spills detected in the SAR images, to extract the backscatter values for each pixel along the section. The lowest backscatter average was observed by the heavy oil spill in the Corsica Island study (−29,99 dB). The highest level of weathering had the highest backscatter averages. Damping rates ranged between 4,12 and 7,07 dB and the backscatter values may be related to low oil layer thickness. Furthermore, low wind speeds may have reduced the contrast between water and oil spills, resulting in low damping ratios in all events.
- Published
- 2023
- Full Text
- View/download PDF
4. A new conditional random field based on mixture of generalized Gaussian model for synthetic aperture radar image segmentation.
- Author
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Golpardaz, Maryam, Helfroush, Mohammad Sadegh, and Danyali, Habibollah
- Subjects
- *
SYNTHETIC aperture radar , *GAUSSIAN mixture models , *IMAGE segmentation , *SYNTHETIC apertures , *RANDOM fields , *POTENTIAL functions , *LOGISTIC regression analysis - Abstract
In this paper, we propose a new algorithm using a conditional random field (CRF) model based on texture features for Synthetic Aperture Radar (SAR) image segmentation. Using the benefit of contourlet transform in describing the texture of SAR image, first, we extract contourlet coefficients from the image. Then, to take advantage of the simultaneous use of low- and high-frequency contourlet subbands, we apply the mixture of generalized Gaussian model (MoGGM) on all contourlet sub-bands to obtain more accurate texture features. Suggesting a new unary potential function based on MoGGM in our proposed CRF, we no longer require estimating the parameters in the multinominal logistic regression (MLR) model in previous CRF methods. Furthermore, we utilize the fifth-order moment to estimate the parameters of MoGGM for achieving better statistical properties of a specific region in SAR images and improving the accuracy of the texture recognition process. The experimental analysis demonstrates that segmentation results using the proposed algorithm are effectively improved compared to the previous CRF methods for SAR image segmentation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
5. Development of processing and simulation strategies for future SAR systems
- Author
-
Kinnunen, Tim
- Subjects
SAR simulation ,SAR processing - Published
- 2023
6. 보간법 기반 가변 PRF 스퀸트 Spotlight SAR 처리 기법.
- Author
-
이 기 웅
- Subjects
SYNTHETIC aperture radar ,INTERPOLATION algorithms ,CELL migration ,SIGNAL processing ,PUNCHED card systems - Abstract
The squinted spotlight SAR(Synthetic Aperture Radar) is an effective imaging mode for obtaining high-resolution SAR imagery in advance. However, a large-range cell migration heavily burdens the storage equipment, and the SAR system should consider its high risk for blind range and Nadir interference. Recently, the PRF(Pulse Repetition Frequency) variation and ASRW(Adaptive Sliding Range Window) have been proposed as effective techniques for squinted SAR image acquisition. This paper presents a signal processing algorithm for the squinted variable PRF spotlight-SAR. The algorithm is a two-step focusing algorithm combined with the interpolation method for compensating distortions due to PRF variation. The simulated variable PRF SAR raw data and processing results demonstrate the validity of the proposed approach. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
7. Processing of Spaceborne Squinted Sliding Spotlight and HRWS TOPS Mode Data Using 2-D Baseband Azimuth Scaling.
- Author
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He, Feng, Dong, Zhen, Zhang, Yongsheng, Jin, Guanghu, and Yu, Anxi
- Subjects
- *
AZIMUTH , *BASEBAND , *SYNTHETIC aperture radar , *PHASE modulation , *ALGORITHMS , *SLIDING mode control - Abstract
This article presents an efficient 2-D baseband azimuth scaling (2-D BAS) approach for the focusing of data acquired in the spaceborne squinted sliding spotlight and high-resolution wide-swath (HRWS) terrain observation by progressive scan (TOPS) imaging modes. The existing approaches can become inefficient or invalid due to the coexistence of central “absolute” and marginal “relative” squint in the above-mentioned modes. In this article, the signal properties of spaceborne squint synthetic aperture radar (SAR) with the antenna electronically steering in the azimuth dimension are analyzed first, based on which a new parity-decomposition-based range equation (PDRE) is presented to dedicatedly model the range histories of targets illuminated by the rotating beam. A novel 2-D BAS approach is then developed to remove the odd asymmetric part but preserve the even symmetric part of PDRE, which means a “true derotation” for eliminating the effect of both absolute and relative squints caused by the beam rotation. An even-order-multinomial perturbation function is applied and integrated into a range-Doppler-based SAR processing kernel to efficiently compensate the azimuth variation of high-order range cell migration (RCM) and azimuth phase modulation caused by the 2-D BAS. The proposed processor is efficient, since none of the data extension, the postprocessing for resolving focused-domain folding, or the 2-D frequency-domain interpolation at high squint is needed. Simulations with point targets in the squinted sliding spotlight and HRWS TOPS modes are used to validate the developed algorithm. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
8. Development and Implementation of Techniques for the Simulation and Processing for Future SAR Systems
- Author
-
Kinnunen, Tim and Kinnunen, Tim
- Abstract
Synthetic Aperture Radar (SAR) is a type of radar system that can generate high-resolution images with which one can detect subtle changes on the scale of centimetres from space. It can operate in any weather condition and during both day and night, making it unique compared to optical sensors. SAR is used for applications such as environmental monitoring, surveillance, and earth observation. Its ability to penetrate clouds and, to some extent, vegetation, allows for insights into terrain, vegetation structure, and even subsurface features. The importance of modelling the generated data of a SAR system before initiating the construction and development of it cannot be overstated. This thesis presents the implementation of the Reverse BackProjection Algorithm (RBPA) designed to generate raw SAR data efficiently and accurately. The RBPA stands out with its flexibility, enabling researchers and designers to simulate and gauge the SAR system's effectiveness under diverse scenarios. This provides an easy way of fine-tuning configurations for distinct needs concerning scene geometries, orbits, and radar designs. Two versions of the RBPA were implemented, differing slightly in the theoretical approach of azimuth defocusing. On top of this, a bistatic mode and Terrain Observation by Progressive Scans (TOPS) acquisition mode was also implemented. The inclusion of these two modes were specifically due to their relevance for the upcoming European Space Agency (ESA) SAR mission, Harmony. The addition of the TOPS mode required a comprehensive design of the antenna framework. Moreover, this implementation also paves the way for simpler integration of modes in the future. The two versions of the RBPA were profiled, revealing the optimal system and parameter configurations.
- Published
- 2023
9. Time-Domain and Monostatic-like Frequency-Domain Methods for Bistatic SAR Simulation
- Author
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Gerardo Di Martino, Antonio Iodice, Antonio Natale, and Daniele Riccio
- Subjects
bistatic SAR ,SAR simulation ,SAR processing ,Chemical technology ,TP1-1185 - Abstract
In recent years, an increasing interest has been devoted to bistatic SAR configurations, which can be effectively used to improve system performance and/or to increase the amount of physical information retrievable from the observed scene. Within this context, the availability of simulation tools is of paramount importance, for both mission planning and processing algorithm verification and testing. In this paper, a time domain simulator useful to obtain the point-spread function and the raw signal for the generic bistatic SAR configuration is presented. Moreover, we focus on the case of two bistatic configurations, which are of considerable interest in actual SAR applications, i.e., the translational invariant SAR and the one-stationary SAR acquisition geometries, for which we obtain meaningful expressions of the Transfer Functions. In particular, these expressions are formally equal to those obtained for the monostatic SAR configuration, so that the already available monostatic simulator can be easily adapted to these bistatic cases. The point-target raw signals obtained using the (exact) time domain simulator and the (approximated) frequency domain one are compared, with special attention to acquisition geometries that may be of practical interest in Formation-Flying SAR applications. Results show that the phase difference between raw signals simulated with the two approaches is, in all cases, smaller (and often much smaller) than about 10 degrees, except that at the very edge of the raw signals, where however, it does not exceed about 50 degrees.
- Published
- 2021
- Full Text
- View/download PDF
10. Coseismic Ground Displacement after the Mw6.2 Earthquake in NW Croatia Determined from Sentinel-1 and GNSS CORS Data
- Author
-
Olga Bjelotomić Oršulić, Danko Markovinović, Matej Varga, and Tomislav Bašić
- Subjects
29 December 2020 hazardous earthquake ,Mw6.2 earthquake in Croatia ,Sentinel-1 ,SAR processing ,coseismic ground displacement ,GNSS ,Geology ,QE1-996.5 - Abstract
At the very end of the year 2020, on 29 December, a hazardous earthquake of Mw = 6.2 hit the area of Petrinja and its surroundings, in the NW of Croatia. The earthquake was felt across the area of 400 km, leaving an inconceivable damage in the vicinity of the epicenter, devastated towns and ruined lives. In order to map the spreading of earthquake waves and to determine the coseismic ground displacement after the mainshock, we have analyzed open satellite radar images of Sentinel-1 and the GNSS data from the nearest CORS station related to the epicenter, along with the seismic faults. In this paper, we addressed and mapped the displacement linear surface ruptures detected by the SAR interferometry. The results show the vertical ground displacement to the extent of −12 cm in the southern area and up to 22 cm in the north-western part of a wide area struck by the earthquake impact, related to the epicenter. Subsidence and uplift in a range of ±5 cm over a wider affected area indicate a spatial extent and hazardous impact made by the earthquake. The ground displacement of 30 cm to the West and 40 cm to the East has been identified considering the intersection of Pokupsko and Petrinja strike-slip fault system in the seismic zone of Pannonian basin. Accordingly, we obtained matching results of 5 cm south-easting shift and −3 cm subsidence on Sisak GNSS CROPOS station, addressing the tectonic blocks movement along the activated complex fault system. The results compared with the geology data confirm the existence of two main faults; the Pokupsko and the Petrinja strike-slip faults and interpret the occurrence of secondary post-seismic events over the observed area.
- Published
- 2021
- Full Text
- View/download PDF
11. Prozessierungsmethoden für multistatische SAR-Konstellationen mit großem Sender-Empfänger-Abstand in Flugrichtung
- Author
-
Sakar, Nida, Eibert, Thomas (Prof. Dr.), and Krieger, Gerhard (Prof. Dr.)
- Subjects
Multistatic SAR ,Ingenieurwissenschaften ,large along-track baseline SAR ,multistatic ,azimuth reconstruction ,digital beamforming ,ddc:620 ,high-resolution wide-swath imaging ,SAR processing - Abstract
This work addresses the topic of advanced processing methods for multistatic SAR constellations with large along-track baselines. The main focus is put on the development of novel azimuth reconstruction approaches that accommodate both range-time and range-frequency dependent terms in the Doppler domain as well as in the time domain. Additionally, the influence of the available technology on the accuracy of the reconstruction are investigated, and then a realistic system concept is identified. Diese Arbeit beschäftigt sich mit fortschrittlichen Prozessierungsmethoden für multistatische SAR-Konstellationen mit großem Sender-Empfänger-Abstand entlang der Flugrichtung. Der Schwerpunkt liegt auf der Entwicklung neuartiger Rekonstruktionsansätze, die sowohl im Dopplerbereich als auch im Zeitbereich Terme mit Entfernungszeit- und Entfernungsfrequenzabhängkeit berücksichtigen. Außerdem wird in dieser Arbeit der Einfluss vorhandener Technologie auf die Exaktheit der Rekonstruktion untersucht und ein realistisches Systemkonzept ausgearbeitet.
- Published
- 2022
12. Space Variance Analysis of the SAR Acquisition Geometry for ROSE-L Images
- Author
-
Gracheva, Valeria, Prats-Iraola, Pau, and Rodriguez-Cassola, Marc
- Subjects
ROSE-L ,space variance ,SAR processing ,ScanSAR - Published
- 2022
13. MIMO-OFDM signal optimization for SAR imaging radar.
- Author
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Baudais, J.-Y., Méric, S., Riché, V., and Pottier, É.
- Subjects
ORTHOGONAL frequency division multiplexing ,SYNTHETIC aperture radar ,ORTHOGONAL arrays - Abstract
This paper investigates the optimization of the coded orthogonal frequency division multiplexing (OFDM) transmitted signal in a synthetic aperture radar (SAR) context. We propose to design OFDM signals to achieve range ambiguity mitigation. Indeed, range ambiguities are well known to be a limitation for SAR systems which operates with pulsed transmitted signal. The ambiguous reflected signal corresponding to one pulse is then detected when the radar has already transmitted the next pulse. In this paper, we demonstrate that the range ambiguity mitigation is possible by using orthogonal transmitted wave as OFDM pulses. The coded OFDM signal is optimized through genetic optimization procedures based on radar image quality parameters. Moreover, we propose to design a multiple-input multiple-output (MIMO) configuration to enhance the noise robustness of a radar system and this configuration is mainly efficient in the case of using orthogonal waves as OFDM pulses. The results we obtain show that OFDM signals outperform conventional radar chirps for range ambiguity suppression and for robustness enhancement in 2 ×2 MIMO configuration. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
14. Advanced InSAR techniques for deformation studies and for simulating the PS-assisted calibration procedure of Sentinel-1 data: case study from Thessaloniki (Greece), based on the Envisat/ASAR archive.
- Author
-
Costantini, Fabiano, Mouratidis, Antonios, Schiavon, Giovanni, and Sarti, Francesco
- Subjects
- *
CALIBRATION , *DEFORMATION of surfaces , *DEFORMATIONS (Mechanics) , *COMPUTER simulation , *GEOTECHNICAL engineering , *REMOTE sensing - Abstract
Using state-of-the-art InSAR techniques, namely persistent scatterers (PSs) and small baseline subset (SBAS) approaches, this study contributes to open geotechnical questions in the area of Thessaloniki (Greece) from a remote-sensing perspective. It also demonstrates the potential of these techniques for calibration purposes, with reference to the new C-band synthetic aperture radar (SAR) sensor on board the Sentinel-1 mission satellites. By exploiting the historical archive of Envisat/ASAR data, as well as a pair of the first Sentinel-1A SAR images, recent (2004–2010) deformation rates up to 18 mm year–1are detected over the study area. These results are then compared to the findings of previous InSAR and geophysical observations, indicating for example, subsidence or tectonic activity. On the other hand, the usefulness of the PS technique is shown over the same region for external SAR calibration purposes. This process simulates the PS-assisted calibration procedure to be applied systematically to Sentinel-1 SAR products. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
15. Analysis of different polarimetric target decomposition methods in forest density classification using C band SAR data.
- Author
-
Varghese, Alappat Ouseph, Suryavanshi, Arun, and Joshi, Asokh Kumar
- Subjects
- *
FOREST density , *CLASSIFICATION algorithms , *MATHEMATICAL decomposition , *POLARIMETRIC remote sensing , *FOREST plants , *SUPPORT vector machines - Abstract
The ability of synthetic aperture radar (SAR) C-band microwave energy to penetrate within forest vegetation makes it possible to extract information on crown components, which in turn gives a better approximation of relative canopy density than optical data-derived canopy density. Many studies have been reported to estimate forest biomass from SAR data, but the scope of C-band SAR in characterizing forest canopy density has not been adequately understood with polarimetric techniques. Polarimetric classification is one of the most significant applications of polarimetric SAR in remote sensing. The objective of the present study was to evaluate the feasibility of different polarimetric SAR data decomposition methods in forest canopy density classification using C-band SAR data. Landsat (Land Satellite) 5 TM (Thematic Mapper) data of the same area has been used as optical data to compare the classification result. RADARSAT (Radar Satellite)-2 image with fine quad-pol obtained on 27 October 2011 over tropical dry forests of Madhav National Park, India, was used for the analysis of full polarimetric data. Six decomposition methods were selected based on incoherent decomposition for generating input images for classification, i.e. Huynen, Freeman and Durden, Yamaguchi, Cloude, Van zyl, and H/A/α. The performance of each decomposition output in relation to each land cover unit present in the study area was assessed using a support vector machine (SVM) classifier. Results show that Yamaguchi 4-component decomposition (overall accuracy 87.66% and kappa coefficient (κ) 0.86) gives better classification results, followed by Van Zyl decomposition (overall accuracy 87.20% andκ0.85) and Freeman and Durden (overall accuracy 86.79% andκ0.85) in forest canopy density classification. Both model-based decompositions (Freeman and Durden and Yamaguchi4) registered good classification accuracy. In eigenvector or eigenvalue decompositions, Van zyl registered the second highest accuracy among different decompositions. The experimental results obtained with polarimetric C-band SAR data over a tropical dry deciduous forest area imply that SAR data have significant potential for estimating canopy density in operational forestry. A better forest density classification result can be achieved within the forest mask (without other land cover classes). The limitations associated with optical data such as non-availability of cloud-free data and misclassification because of gregarious occurrence of bushy vegetation such as Lantana can be overcome by using C-band SAR data. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
16. Near range radar and its application to near surface geophysics and disaster mitigation.
- Author
-
Sato, Motoyuki
- Subjects
- *
HAZARD mitigation , *SYNTHETIC aperture radar , *GROUND penetrating radar , *LAND mine clearance , *REMOTE sensing - Abstract
In this paper, we discuss about the near range radar applied to various environmental applications and disaster mitigation issues. Synthetic aperture radar (SAR) processing or migration is the key technology in near range radar imaging, which can be used in ground penetrating radar (GPR) and ground-based synthetic aperture radar (GB-SAR). We demonstrate some applications which include GPR for humanitarian demining, GPR for archaeological survey, GB-SAR for landslide monitoring and nondestructive inspection of wooden buildings. We also demonstrate a new array GPR system 'Yakumo', which was used for archaeological survey for demonstration of advanced multi-static radar signal processing for better radar imaging. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
17. Coseismic Ground Displacement after the Mw6.2 Earthquake in NW Croatia Determined from Sentinel-1 and GNSS CORS Data
- Author
-
Danko Markovinović, Matej Varga, Tomislav Bašić, and Olga Bjelotomić Oršulić
- Subjects
29 December 2020 hazardous earthquake ,Mw6.2 earthquake in Croatia ,Sentinel-1 ,SAR processing ,coseismic ground displacement ,GNSS ,010504 meteorology & atmospheric sciences ,Mw 6.2 earthquale in Croatia ,Pannonian basin ,0211 other engineering and technologies ,02 engineering and technology ,Fault (geology) ,01 natural sciences ,Displacement (vector) ,Seismic wave ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,geography ,geography.geographical_feature_category ,lcsh:QE1-996.5 ,Subsidence ,lcsh:Geology ,Tectonics ,GNSS applications ,Epicenter ,General Earth and Planetary Sciences ,Geology ,Seismology - Abstract
At the very end of the year 2020, on 29 December, a hazardous earthquake of Mw = 6.2 hit the area of Petrinja and its surroundings, in the NW of Croatia. The earthquake was felt across the area of 400 km, leaving an inconceivable damage in the vicinity of the epicenter, devastated towns and ruined lives. In order to map the spreading of earthquake waves and to determine the coseismic ground displacement after the mainshock, we have analyzed open satellite radar images of Sentinel-1 and the GNSS data from the nearest CORS station related to the epicenter, along with the seismic faults. In this paper, we addressed and mapped the displacement linear surface ruptures detected by the SAR interferometry. The results show the vertical ground displacement to the extent of -12 cm in the southern area and up to 22 cm in the north-western part of a wide area struck by the earthquake impact, related to the epicenter. Subsidence and uplift in a range of +/- 5 cm over a wider affected area indicate a spatial extent and hazardous impact made by the earthquake. The ground displacement of 30 cm to the West and 40 cm to the East has been identified considering the intersection of Pokupsko and Petrinja strike-slip fault system in the seismic zone of Pannonian basin. Accordingly, we obtained matching results of 5 cm south-easting shift and -3 cm subsidence on Sisak GNSS CROPOS station, addressing the tectonic blocks movement along the activated complex fault system. The results compared with the geology data confirm the existence of two main faults; the Pokupsko and the Petrinja strike-slip faults and interpret the occurrence of secondary post-seismic events over the observed area., Geosciences, 11 (4), ISSN:2076-3263
- Published
- 2021
18. Extension of Wavenumber Domain Focusing for spotlight COSMO-SkyMed SAR Data.
- Author
-
Lorusso, Rino, Nicoletti, Marco, Gallipoli, Antonella, Lorè, Vita Antonia, Milillo, Giovanni, Lombardi, Nunzia, and Nirchio, Francesco
- Subjects
WAVENUMBER ,SYNTHETIC aperture radar ,LOW earth orbit satellites - Abstract
In this work we describe a method to handle curved orbits in wavenumber domain focusing algorithm for high-resolution SAR data acquired by Low Earth Orbit satellites using spotlight mode. The standard wavenumber domain focusing algorithm make assumptions that start to be invalid when applied to high-resolution spotlight SAR data acquired in spaceborne low Earth orbit (LEO) configurations. The assumption of a hyperbolic range history is no longer accurate for sub-metric spatial resolutions due to the satellite curved orbit. The proposed method is used to estimate the satellite velocity and closest-approach range distance of the rectified effective orbit which minimizes the phase errors over the whole scene coverage. This allows to use all frequency domain focusing kernels developed to focus SAR images acquired with a stripmap mode. We use this method with the - k algorithm, and its approximation Fast ω-k (Fω-k), demonstrating its effectiveness to focus COSMO-SkyMed (CSK) SAR images obtaining, respectively, sub-metric and metric azimuth spatial resolution. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
19. Time-domain and monostatic-like frequency-domain methods for bistatic SAR simulation
- Author
-
Antonio Natale, Daniele Riccio, Gerardo Di Martino, Antonio Iodice, Di Martino, G., Iodice, A., Natale, A., and Riccio, D.
- Subjects
Computer science ,0211 other engineering and technologies ,Context (language use) ,TP1-1185 ,02 engineering and technology ,Biochemistry ,Transfer function ,Signal ,Article ,Analytical Chemistry ,SAR simulation ,Physical information ,0202 electrical engineering, electronic engineering, information engineering ,bistatic SAR ,Time domain ,Electrical and Electronic Engineering ,Instrumentation ,SAR processing ,021101 geological & geomatics engineering ,Chemical technology ,020206 networking & telecommunications ,Atomic and Molecular Physics, and Optics ,Bistatic radar ,Frequency domain ,Focus (optics) ,Algorithm - Abstract
In recent years, an increasing interest has been devoted to bistatic SAR configurations, which can be effectively used to improve system performance and/or to increase the amount of physical information retrievable from the observed scene. Within this context, the availability of simulation tools is of paramount importance, for both mission planning and processing algorithm verification and testing. In this paper, a time domain simulator useful to obtain the point-spread function and the raw signal for the generic bistatic SAR configuration is presented. Moreover, we focus on the case of two bistatic configurations, which are of considerable interest in actual SAR applications, i.e., the translational invariant SAR and the one-stationary SAR acquisition geometries, for which we obtain meaningful expressions of the Transfer Functions. In particular, these expressions are formally equal to those obtained for the monostatic SAR configuration, so that the already available monostatic simulator can be easily adapted to these bistatic cases. The point-target raw signals obtained using the (exact) time domain simulator and the (approximated) frequency domain one are compared, with special attention to acquisition geometries that may be of practical interest in Formation-Flying SAR applications. Results show that the phase difference between raw signals simulated with the two approaches is, in all cases, smaller (and often much smaller) than about 10 degrees, except that at the very edge of the raw signals, where however, it does not exceed about 50 degrees.
- Published
- 2021
- Full Text
- View/download PDF
20. Processing of sliding spotlight SAR data in presence of squint.
- Author
-
Zamparelli, V., Fornaro, G., Lanari, R., Perna, S., and Reale, D.
- Abstract
In this paper we discuss the extension of an algorithm for efficient processing of SAR data acquired in sliding spotlight mode based on a two-step approach. The two-step spotlight data processing procedure, already introduced in the literature, is a very simple and effective procedure because it is based on a plain use of classical (i.e. stripmap mode) SAR processing codes. The algorithm here proposed extends the two-step approach in such a way t account for the presence of squint. Experiments have been carried out on simulated data to clarify the rationale of the method and to confirm its validity. Results obtained by processing real data of the COSMO-SKYMED constellation are also presented. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
21. High precision SAR focusing of TerraSAR-X experimental staring spotlight data.
- Author
-
Prats-Iraola, Pau, Scheiber, Rolf, Rodriguez-Cassola, Marc, Wollstadt, Steffen, Mittermayer, Josef, Brautigam, Benjamin, Schwerdt, Marco, Reigber, Andreas, and Moreira, Alberto
- Abstract
This paper addresses several innovative steps needed in the chirp scaling and extended chirp scaling (ECS) algorithms in order to process staring Spotlight TerraSAR-X (TSX) images with 21 cm azimuth resolution and 300 MHz range bandwidth. The aspects that need of special consideration are the 2D phase truncation in frequency domain of ECS, the element pattern of the antenna array, the curved orbit, the stop-and-go approximation, and the troposphere. All these aspects are expounded in detail and a solution is given for each of them. The suggested corrections are applied at raw data level, hence easing the integration within the existing TSX processor. Real data acquired by TSX in the experimental staring Spotlight mode are used to validate the proposed methodology. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
22. On the Processing of Very High Resolution Spaceborne SAR Data.
- Author
-
Prats-Iraola, Pau, Scheiber, Rolf, Rodriguez-Cassola, Marc, Mittermayer, Josef, Wollstadt, Steffen, De Zan, Francesco, Brautigam, Benjamin, Schwerdt, Marco, Reigber, Andreas, and Moreira, Alberto
- Subjects
- *
SYNTHETIC aperture radar , *BANDWIDTH research , *SIGNAL theory , *ANTENNA arrays , *BURST noise - Abstract
This paper addresses several important aspects that need to be considered for the processing of spaceborne synthetic aperture radar (SAR) data with resolutions in the decimeter range. In particular, it will be shown how the motion of the satellite during the transmission/reception of the chirp signal and the effect of the troposphere deteriorate the impulse response function if not properly considered. Further aspects that have been investigated include the curved orbit, the array pattern for electronically steered antennas, and several considerations within the processing itself. For each aspect, a solution is proposed, and the complete focusing methodology is expounded and validated using simulated point targets and staring spotlight data acquired by TerraSAR-X with 16-cm azimuth resolution and 300-MHz range bandwidth. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
23. Efficient Evaluation of Fourier-Based SAR Focusing Kernels.
- Author
-
Prats-Iraola, Pau, Rodriguez-Cassola, Marc, De Zan, Francesco, Lopez-Dekker, Paco, Scheiber, Rolf, and Reigber, Andreas
- Abstract
This letter addresses the efficient evaluation of Fourier-based kernels for synthetic aperture radar (SAR) image formation. The goal is to evaluate the quality of the focused impulse response function and the residual phase errors of the kernel without having to implement the processor itself nor perform a costly point-target simulation followed by the processing. The proposed methodology is convenient for situations where the assumption of a hyperbolic range history does not hold anymore, and hence, a compact analytic expression of the point target spectrum is not available. Examples where the hyperbolic range history does not apply include very high resolution spaceborne SAR imaging or bistatic SAR imaging. The approach first numerically computes the 2-D spectrum of a point target and then uses the transfer function of the focusing kernel to match it. The spectral support is then computed to adapt the spectrum to the output imaging geometry, so that the impulse response function (IRF) is finally obtained. The proposed approach is valid under the assumption of a large time-bandwidth product, as is usually the case for current air- and spaceborne SAR sensors. The methodology is validated by comparing the matched IRFs with the ones obtained using point-target simulations. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
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24. Prospection and Monitoring of the Archaeological Heritage of Nasca, Peru, with ENVISAT ASAR.
- Author
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Tapete, Deodato, Cigna, Francesca, Masini, Nicola, and Lasaponara, Rosa
- Subjects
- *
SYNTHETIC aperture radar , *BACKSCATTERING , *AQUEDUCTS , *REMOTE-sensing images , *ARCHAEOLOGICAL excavations - Abstract
ABSTRACT The processing method based on synthetic aperture radar (SAR) amplitude information presented by Cigna et al. (2013, this issue) was used to extract the backscattering coefficient ( σ0) from ENVISAT advanced SAR (ASAR) scenes to investigate the archaeological heritage of the Nasca region, southern Peru. Average backscattering and σ0 time series in 2003-2007 were obtained for some of the most famous groups of the Nazca Lines, as well as for the adobe structures of the Ceremonial Centre of Cahuachi, and allowed the recognition of anthropogenic features on arid and bare soil. Despite the expected constraints due to the medium spatial resolution of the ASAR scenes (~30 m), some features related to the Nasca ancient aqueduct systems ( puquios) were detected, and water level changes were inferred from amplitude change detection maps and σ0 time series. The SAR-based prospection results were also compared with a vegetation index derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for 2003, 2004 and 2007. The changes observed over Cahuachi and the neighbouring archaeological mounds are then discussed in light of the recent conservation history of the site and the contemporary archaeological excavations. The research opens interesting perspectives for routine use of SAR data for purposes of archaeological prospection and condition monitoring in (semi-)arid and desert regions. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
25. Amplitude Change Detection with ENVISAT ASAR to Image the Cultural Landscape of the Nasca Region, Peru.
- Author
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Cigna, Francesca, Tapete, Deodato, Lasaponara, Rosa, and Masini, Nicola
- Subjects
- *
CULTURAL landscapes , *BACKSCATTERING , *AMPLITUDE estimation , *LAND use , *REMOTE-sensing images , *SYNTHETIC aperture radar - Abstract
ABSTRACT Synthetic aperture radar (SAR) amplitude information from ENVISAT C-band advanced SAR (ASAR) data was used to analyse the cultural landscape of the Nasca region, southern Peru. A multispatial environmental analysis was performed over the whole drainage basin of the Rio Grande, by extracting the radar backscattering coefficient ( σ0) of both natural and anthropogenic features between 2003 and 2005. Co-registration of the ASAR scenes to a single master resulted in precisions of less than 0.1 pixels along both the range and azimuth directions. Four different products were generated based on the co-registered ASAR stack: (i) temporally averaged radar signatures of the targets between 2003 and 2005; (ii) time series of spatially averaged radar signatures within selected areas of interest; (iii) amplitude change detection products based on (iii) image ratios and (iv) RGB colour composites between different scenes. Comparisons of annual and seasonal records through amplitude change detection maps highlighted σ0 changes over the floodplains of the Rio Ingenio and Rio Nazca, which correlate well with evidence from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data acquired in 2003, 2004 and 2007. Inferences about land use and soil conditions were retrieved from the σ0 change patterns, thereby proving the capability of this approach to support landscape evolution studies, even with SAR imagery of medium resolution (~30 m). Our results also demonstrated actual potential for monitoring mass movements and land surface processes, to assess the susceptibility of archaeological heritage and cultural landscape to natural hazards. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
26. Efficient Full Aperture Processing of TOPS Mode Data Using the Moving Band Chirp Z-Transform.
- Author
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Engen, Geir and Larsen, Yngvar
- Subjects
- *
SYNTHETIC aperture radar , *Z transformation , *AZIMUTH , *ANTENNAS (Electronics) , *BANDWIDTHS , *DOPPLER effect , *IMAGING systems - Abstract
The main operational mode of the European Space Agency's upcoming Sentinel-1 operational satellite will be the Terrain Observation by Progressive Scans (TOPS) imaging mode. This paper presents a very efficient wavenumber domain processor for the processing of TOPS mode data. In particular, a novel signal transform, called a moving band chirp Z-transform, is introduced in order to allow the entire azimuth aperture to be focused simultaneously without any need for temporary unaliasing, which requires upsampling, or subaperture processing. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
27. 3-D Time-Domain SAR Imaging of a Forest Using Airborne Multibaseline Data at L- and P-Bands.
- Author
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Frey, Othmar and Meier, Erich
- Subjects
- *
SYNTHETIC aperture radar , *IMAGING systems , *TOMOGRAPHY , *REMOTE sensing , *SIGNAL processing , *RADAR in aeronautics , *BEAMFORMING - Abstract
In this paper, a time-domain back-projection based tomographic processing approach to a 3-D reconstruction grid is detailed, with the focusing in the third dimension being either modified versions of multilook standard beamforming, robust Capon beamforming, or multiple signal classification. The novel feature of the proposed approach compared to previous synthetic aperture radar (SAR) tomography approaches is that it allows for an approximation-free height-dependent calculation of the sample covariance matrix by exploiting the azimuth-focused data on the 3-D reconstruction grid. The method is applied to experimental multibaseline quad-pol SAR data at L- and P-bands acquired by German Aerospace Center's (DLR) E-SAR sensor: Tomographic images of a partially forested area, including a 3-D voxel plot that visualizes the very high level of detail of the tomographic image, are shown, and an analysis of the focusing performance is given for the full as well as reduced synthetic aperture in the normal direction. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
28. Geodetically Accurate InSAR Data Processor.
- Author
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Zebker, Howard A., Hensley, Scott, Shanker, Piyush, and Wortham, Cody
- Subjects
- *
SYNTHETIC aperture radar , *ELECTRONIC data processing , *INTERFEROMETRY , *IMAGING systems , *REMOTE-sensing images , *EQUATIONS , *IMAGE analysis - Abstract
We present a new interferometric synthetic aperture radar (InSAR) processing approach that capitalizes on the precise orbit tracking that is available with modern radar satellites. Our method uses an accurate orbit information along with motion-compensation techniques to propagate the radar echoes to positions along a noninertial virtual orbit frame in which the location and focusing equations are particularly simple, so that images are focused without requiring autofocus techniques and are computed efficiently. Motion compensation requires two additional focus correction phase terms that are implemented in the frequency domain. If the images from an interferometric pair or stack are all computed along the same reference orbit, flat-Earth topographic correction is not needed, and image coregistration is simplified, obviating many difficulties that are often encountered in InSAR processing. We process several data sets collected by the ALOS PALSAR instrument and find that the geodetic accuracy of the radar images is 10–20 m, with up to 20 m of additional image distortion needed to align 100 km \times 100 km scenes with reference digital elevation models. We validated the accuracy by using both known radar corner reflector locations and by the registration of the interferograms with digital maps. The topography-corrected interferograms are free from all geometric phase terms, and they clearly show the geophysical observables of crustal deformation, atmospheric phase, and ionospheric phase. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
29. Measurement of Ionospheric TEC in Spaceborne SAR Data.
- Author
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Jehle, Michael, Frey, Othmar, Small, David, and Meier, Erich
- Subjects
- *
RADAR , *SYNTHETIC aperture radar , *ELECTRONS , *AZIMUTH , *IONOSPHERE - Abstract
The propagation of spaceborne radar signals operating at L-band frequency or below can be seriously affected by the ionosphere. At high states of solar activity, Faraday rotation (FR) and signal path delays disturb radar polarimetry and reduce resolution in range and azimuth. While these effects are negligible at X-band, FR and the frequency-dependent path delays can become seriously problematic starting at L-band. For quality assurance and calibration purposes, existing L-band or potential spaceborne P-band missions require the estimation of the ionospheric state before or during the data take. This paper introduces two approaches for measuring the ionospheric total electron content (TEC) from single-polarized spaceborne SAR data. The two methods are demonstrated using simulations. Both methods leverage knowledge of the frequency-dependent path delay through the ionosphere: The first estimates TEC from the phase error of the filter mismatch, while the second gauges path-delay differences between up and down chirps. FR, mean (direct current) offsets, and noise contributions are also considered in the simulations. Finally, possibilities for further methodological improvements are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
30. Processing of Sliding Spotlight and TOPS SAR Data Using Baseband Azimuth Scaling.
- Author
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Prats, Pau, Scheiber, Rolf, Mittermayer, Josef, Meta, Adriano, and Moreira, Alberto
- Subjects
- *
AZIMUTH , *SYNTHETIC aperture radar , *IMAGING systems , *SCANNING systems , *ANTENNAS (Electronics) - Abstract
This paper presents an efficient phase preserving processor for the focusing of data acquired in sliding spotlight and Terrain Observation by Progressive Scans (TOPS) imaging modes. They share in common a linear variation of the Doppler centroid along the azimuth dimension, which is due to a steering of the antenna (either mechanically or electronically) throughout the data take. Existing approaches for the azimuth processing can become inefficient due to the additional processing to overcome the folding in the focused domain. In this paper, a new azimuth scaling approach is presented to perform the azimuth processing, whose kernel is exactly the same for sliding spotlight and TOPS modes. The possibility to use the proposed approach to process data acquired in the ScanSAR mode, as well as a discussion concerning staring spotlight, is also included. Simulations with point targets and real data acquired by TerraSAR-X in sliding spotlight and TOPS modes are used to validate the developed algorithm. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
31. Comment on “Measurement of Ionospheric TEC in Spaceborne SAR Data”.
- Author
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Zhang, Yongsheng, Jehle, Michael, Li, Dong, Zhen, and Liang, Diannong
- Subjects
- *
SYNTHETIC aperture radar , *IONOSPHERIC research , *ATMOSPHERIC physics , *SPACE-based radar , *REMOTE sensing by radar - Abstract
Two novel approaches for measuring the ionospheric total electron content (TEC) from single-polarized spaceborne SAR data were proposed in the mentioned paper, i.e., the TEC autofocus method and the systematic alternate up/down pulse methodology. The up/down pulse methodology indicates that ionospheric TEC could be estimated using the difference between range-compressed phase distributions of the up and down chirps. However, it can be shown theoretically that the difference between the up and down chirps after compression is not expected. Thus, the estimation of TEC from alternating up versus down chirp combinations might not be feasible. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
32. A Spatially Adjusted Elevation Model in Dronning Maud Land, Antarctica, Based on Differential SAR Interferometry.
- Author
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Drews, Reinhard, Rack, Wolfgang, Wesche, Christine, and Helm, Veit
- Subjects
- *
ICE sheets , *ALTITUDES , *SYNTHETIC aperture radar , *INTERFEROMETRY , *REMOTE sensing - Abstract
In this paper, a new digital elevation model (DEM) is derived for the ice sheet in western Dronning Maud Land, Antarctica. It is based on differential interferometric synthetic aperture radar (SAR) from the European Remote Sensing 1/2 (ERS-1/2) satellites, in combination with ICESat's Geoscience Laser Altimeter System (GLAS). A DEM mosaic is compiled out of 116 scenes from the ERS-1 ice phase in 1994 and the ERS-1/2 tandem mission between 1996 and 1997 with the GLAS data acquired in 2003 that served as ground control. Using three different SAR processors, uncertainties in phase stability and baseline model, resulting in height errors of up to 20 m, are exemplified. Atmospheric influences at the same order of magnitude are demonstrated, and corresponding scenes are excluded. For validation of the DEM mosaic, covering an area of about 130 000 km² on a 50-m grid, independent ICESat heights ,(2004-2007), ground-based kinematic GPS (2005), and airborne laser scanner data (ALS, 2007) are used. Excluding small areas with low phase coherence, the DEM differs in mean and standard deviation by 0.5 + / - 10.1, 1.1 + / - 6.4, and 3.1 + / - 4.0 m from ICESat, GPS, and ALS, respectively. The excluded data points may deviate by more than 50 m. In order to suppress the spatially variable noise below a 5-m threshold, 18% of the DEM area is selectively averaged to a final product at varying horizontal spatial resolution. Apart from mountainous areas, the new DEM outperforms other currently available DEMs and may serve as a benchmark for future elevation models such as from the TanDEM-X mission to spatially monitor ice sheet elevation. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
33. Near real-time parallel processing and advanced data management of SAR images in grid environments.
- Author
-
Cafaro, Massimo, Epicoco, Italo, Fiore, Sandro, Lezzi, Daniele, Mocavero, Silvia, and Aloisio, Giovanni
- Abstract
In this paper, we describe the process of parallelizing an existing, production level, sequential Synthetic Aperture Radar (SAR) processor based on the Range-Doppler algorithmic approach. We show how, taking into account the constraints imposed by the software architecture and related software engineering costs, it is still possible with a moderate programming effort to parallelize the software and present an message-passing interface (MPI) implementation whose speedup is about 8 on 9 processors, achieving near real-time processing of raw SAR data even on a moderately aged parallel platform. Moreover, we discuss a hybrid two-level parallelization approach that involves the use of both MPI and OpenMP. We also present GridStore, a novel data grid service to manage raw, focused and post-processed SAR data in a grid environment. Indeed, another aim of this work is to show how the processed data can be made available in a grid environment to a wide scientific community, through the adoption of a data grid service providing both metadata and data management functionalities. In this way, along with near real-time processing of SAR images, we provide a data grid-oriented system for data storing, publishing, management, etc. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
34. Focusing of Airborne Synthetic Aperture Radar Data From Highly Nonlinear Flight Tracks.
- Author
-
Frey, Othmar, Magnard, Christophe, Rüegg, Maurice, and Meier, Erich
- Subjects
- *
SYNTHETIC aperture radar , *IMAGING systems , *COHERENT radar , *ARTIFICIAL satellite tracking , *REMOTE sensing , *ARTIFICIAL satellites , *ELECTRONIC surveillance - Abstract
Standard focusing of data from synthetic aperture radar (SAR) assumes a straight recording track of the sensor platform. Small nonlinearities of airborne platform tracks are corrected for during a motion-compensation step while maintaining the assumption of a linear flight path. This paper describes the processing of SAR data acquired from nonlinear tracks, typical of sensors mounted on small aircraft or drones flying at low altitude. Such aircraft do not fly along straight tracks, but the trajectory depends on topography, influences of weather and wind, or the shape of areas of interest such as rivers or traffic routes. Two potential approaches for processing SAR data from such highly nonlinear flight tracks are proposed, namely, a patchwise frequency-domain processing and mosaicking technique and a time-domain back-projection-based technique. Both are evaluated with the help of experimental data featuring tracks with altitude changes, a double bend, a 90° curve, and a linear flight track. In order to assess the quality of the focused data, close-ups of amplitude images are compared, impulse response functions of a point target are analyzed, and the coherence is evaluated. The experimental data were acquired by the German Aerospace Center's E-SAR L-band system. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
35. Measurement of Ionospheric Faraday Rotation in Simulated and Real Spaceborne SAR Data.
- Author
-
Jehle, Michael, Rüegg, Maurice, Zuberbühler, Lukas, Small, David, and Meier, Erich
- Subjects
- *
SIMULATION methods & models , *OPTICAL polarization , *OPTICAL measurements , *SYNTHETIC aperture radar , *IONOSPHERE , *BROADBAND communication systems , *IMAGING systems , *ELECTROMAGNETIC waves , *REMOTE sensing - Abstract
The influence of the atmosphere on a frequency-modulated electromagnetic wave traversing the ionosphere is becoming increasingly important for recent and upcoming low-frequency and wide-bandwidth spaceborne synthetic aperture radar (SAR) systems. The ionized ionosphere induces Faraday rotation (FR) at these frequencies that affects radar polarimetry and causes signal path delays resulting in a reduced range resolution. The work at hand introduces a simulation model of SAR signals passing through the atmosphere, including both frequency-dependent FR and path delays. Based on simulation results from this model [proven with real Advanced Land Observing Satellite Phased Array L-band Synthetic Aperture Radar (PALSAR) data], estimation of FR in quad-polarized SAR data using the given approach is shown for raw, range-compressed, and focused radar images. Path delays and signal chirp bandwidth effects are considered. Investigations discuss the suitability of raw and compressed data versus combination of total electron content maps with the Earth's magnetic field for FR estimation and deduced from a large number of analyzed PALSAR data sets. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
36. Estimation of the Temporal Evolution of the Deformaltion Using Airborne Differential SAR Interferometry.
- Author
-
Prats, Pau, Reigber, Andreas, Mallorquí, Jordi J., Scheiber, Rolf, and Moreira, Alberto
- Subjects
- *
SYNTHETIC aperture radar , *COHERENT radar , *RADAR , *INTERFEROMETRY , *IMAGE , *OPTICAL measurements - Abstract
This paper presents airborne differential synthetic aperture radar (SAR) interferometry results using a stack of 14 images, which were acquired by the Experimental SAR system of the German Aerospace Center (DLR) during a time span of 2.5 h. An advanced differential technique is used to retrieve the error in the digital elevation model and the temporal evolution of the deformation for every coherent pixel in the image. The two main limitations in airborne SAR processing are analyzed, namely, the existence of residual motion errors (RMEs) (inaccuracies in the navigation system on the order of 1-5 cm) and the accommodation of the topography and the aperture dependence on motion errors during the processing. The coupling between them is also addressed, showing that the estimation of the differential RME, i.e., baseline error, can be biased when using techniques based on the coregistration between interferometric looks. The SAR focusing chain to process the data is also presented together with the modifications in the differential interferometry processor deal with the remaining baseline error. The detected motion to of a corner reflector and the measured deformation in several agricultural fields allows one to validate the proposed techniques. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
37. A Keystone Transform Without Interpolation for SAR Ground Moving-Target Imaging.
- Author
-
Daiyin Zhu, Yong Li, and Zhaoda Zhu
- Abstract
Synthetic aperture radar (SAR) image formation for a ground moving target necessitates the compensation of the unknown target trajectory. The keystone transform has been employed to remove the linear component of the range migration for the moving target, where interpolation is required. In this letter, a realization of the keystone transform avoiding interpolation is presented. The kernel of this transform, i.e., the range-frequency-dependent azimuth time rescaling, is implemented using only complex multiplications and fast Fourier transforms based on the scaling principle, which has been successfully applied in the equalization of the space-variant range cell migration in SAR processing. In addition, the moving target is coarsely focused according to the SAR geometry and the platform velocity while exploiting the scaling principle. This preliminary focusing is helpful in the isolation of the moving target from ground clutter, so as to facilitate a more refined processing with respect to each mover. SAR raw data combined with simulated echoes of moving targets are utilized to validate the presented approach [ABSTRACT FROM PUBLISHER]
- Published
- 2007
- Full Text
- View/download PDF
38. Modified range-Doppler processing for FM-CW synthetic aperture radar.
- Author
-
de Wit, J.J.M., Meta, A., and Hoogeboom, P.
- Abstract
The combination of compact frequency-modulated continuous-wave (FM-CW) technology and high-resolution synthetic aperture radar (SAR) processing techniques should pave the way for the development of a lightweight, cost-effective, high-resolution, airborne imaging radar. Regarding FM-CW SAR signal processing, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. In FM-CW SAR, the so-called stop-and-go approximation is no longer valid due to the relatively long sweeps that FM-CW radars transmit. The main effect of the continuous motion is a Doppler frequency shift throughout the SAR observation time. This Doppler frequency shift can be compensated for by modifying the range migration compensation. [ABSTRACT FROM PUBLISHER]
- Published
- 2006
- Full Text
- View/download PDF
39. ON THE USE OF TIME-DOMAIN SAR FOCUSING IN SPACEBORNE SAR MISSIONS
- Author
-
Marc Rodriguez-Cassola, Pau Prats-Iraola, Alberto Moreira, and Gerhard Krieger
- Subjects
020301 aerospace & aeronautics ,numerical Omega-k ,Computer science ,fast-factorized backprojection ,Use of time ,0211 other engineering and technologies ,Process (computing) ,02 engineering and technology ,Variance (accounting) ,Domain (software engineering) ,0203 mechanical engineering ,spaceborne SAR ,Relevance (information retrieval) ,Time domain ,SAR processing ,021101 geological & geomatics engineering ,Remote sensing - Abstract
This paper discusses the relevance and use of efficient focusing in the time domain in spaceborne SAR. With the increasing number of space-variant corrections required by higher resolution and wide swath observations, the efficiency of SAR focusing algorithms in the Fourier domain drops significantly. The main sources of space variance to be faced in future spaceborne SAR missions and their implications on the complexity of the focusing process are discussed. The paper also presents a direct comparison between time-domain and frequency-domain approaches, providing an estimate of the computational burden of a fast-factorized backprojection algorithm compared to a sophisticated numerical ωk, identifying the operation areas where the the former may show an efficiency advantage.
- Published
- 2019
40. Time-Domain and Monostatic-like Frequency-Domain Methods for Bistatic SAR Simulation.
- Author
-
Di Martino, Gerardo, Iodice, Antonio, Natale, Antonio, and Riccio, Daniele
- Subjects
- *
ALGORITHMS , *PRODUCTION planning , *GEOMETRY - Abstract
In recent years, an increasing interest has been devoted to bistatic SAR configurations, which can be effectively used to improve system performance and/or to increase the amount of physical information retrievable from the observed scene. Within this context, the availability of simulation tools is of paramount importance, for both mission planning and processing algorithm verification and testing. In this paper, a time domain simulator useful to obtain the point-spread function and the raw signal for the generic bistatic SAR configuration is presented. Moreover, we focus on the case of two bistatic configurations, which are of considerable interest in actual SAR applications, i.e., the translational invariant SAR and the one-stationary SAR acquisition geometries, for which we obtain meaningful expressions of the Transfer Functions. In particular, these expressions are formally equal to those obtained for the monostatic SAR configuration, so that the already available monostatic simulator can be easily adapted to these bistatic cases. The point-target raw signals obtained using the (exact) time domain simulator and the (approximated) frequency domain one are compared, with special attention to acquisition geometries that may be of practical interest in Formation-Flying SAR applications. Results show that the phase difference between raw signals simulated with the two approaches is, in all cases, smaller (and often much smaller) than about 10 degrees, except that at the very edge of the raw signals, where however, it does not exceed about 50 degrees. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
41. The BIOMASS Ground Processor Prototype: An Overview
- Author
-
Prats-Iraola, Pau, Papathanassiou, Konstantinos, Kim, Jun Su, Rodriguez-Cassola, Marc, D'Aria, Davide, Piantanida, Riccardo, Valentino, Antonio, Giudici, Davide, Jäger, Marc, Scheiber, Rolf, Pinheiro, Muriel, Yague-Martinez, Nestor, Nannini, Matteo, Gracheva, Valeria, Guardabrazo, Tomás, and Moreira, Alberto
- Subjects
RFI ,ionosphere ,Synthetic Aperture Radar ,SAR processing ,BIOMASS - Published
- 2018
42. Imagerie SAR haute résolution aéroportée
- Author
-
Oriot, Hélène, DEMR, ONERA, Université Paris Saclay (COmUE) [Palaiseau], Université Paris Saclay (COmUE)-ONERA, UNIVERSITE DE PARIS-SUD CENTRE D'ORSAY, and Sylvie MARCOS
- Subjects
[PHYS]Physics [physics] ,SYSTEME RADAR ,IMAGERIE SAR ,INTERFEROMETRIE ,DETECTION CIBLE MOBILE ,SAR PROCESSING ,AEROPORTEE ,SAR IMAGERY ,RADAR ,INTERFEROMETRY ,[SPI]Engineering Sciences [physics] ,RADAR SYSTEM ,GMTI ,AIRBORNE SENSOR - Abstract
With the growing number of operating spatial systems, SAR imagery has become a major topic of research in the remote sensing community. In France, most of the research focuses on the exploitation of satellite SAR images. On the contrary, given the lower availability of such data, the airborne domain concerns a smaller community. This report aims at presenting the specificities of high-resolution airborne radar imagery and their impacts on multi-channel applications.A first part is devoted to a theoretical analysis of airborne SAR processing in its different modalities. The various SAR processing approaches adapted to high resolution are presented from a geometric point of view rather than frequential point of view. Then, the principles of multichannel processing are presented with emphasis on the phenomenology associated with the improvement of the resolution: link between image registration and interferometric phase, behavior of point like scatterers, anisotropic or surfacic backscatters. A second part is dedicated to the impact of real acquisition systems on SAR processing and multichannel applications. Issues related to the radar hardware, the antenna particularities, non-linearities of the trajectories are discussed and illustrated on applications such as calibration of polarimetric data, 3D extraction, ground moving target detection .; Avec la multiplication des systèmes spatiaux, l’imagerie radar fait l’objet de nombreux travaux de recherche. En France, la majorité des travaux se concentre sur l’exploitation des images radar spatiales, de résolution de plus en plus fine. Le domaine aéroporté concerne une communauté plus restreinte étant donnée la moindre disponibilité de telles données. Ce rapport a pour vocation de présenter les spécificités de l’imagerie radar aéroportée haute résolution et d’en comprendre les impacts sur les applications multi-voies.Une première partie est consacrée à l’analyse théorique du traitement SAR aéroporté dans ses différentes modalités. Les diverses approches de traitement SAR adaptés à la haute résolution sont présentées selon un point de vue géométrique plutôt que fréquentiel. Puis, toujours sous ce même angle, les principes des traitements multivoies sont abordés en insistant sur les phénomènes apparaissant avec l’amélioration de la résolution : lien entre recalage d’images et phase interférométrique, comportement des rétrodiffuseurs ponctuels, surfaciques et anisotropes.Une deuxième partie est consacrée à l’étude de l’impact d’un système réel d’acquisition sur le traitement SAR et les applications multivoies. Les problématiques liées à la chaîne radar, aux diagrammes d’antennes, aux trajectoires non linéaires sont abordées.Enfin, différents travaux d’exploitation d’images radar haute résolution aéroportées (calibration de données polarimétriques, extraction du 3D sur les images SAR, détection de cibles mobiles) illustrent le propos.
- Published
- 2018
43. Airborne high resolution SAR imagery
- Author
-
Oriot, Hélène, André, Cécile, DEMR, ONERA, Université Paris Saclay (COmUE) [Palaiseau], Université Paris Saclay (COmUE)-ONERA, UNIVERSITE DE PARIS-SUD CENTRE D'ORSAY, and Sylvie MARCOS
- Subjects
[PHYS]Physics [physics] ,SYSTEME RADAR ,IMAGERIE SAR ,INTERFEROMETRIE ,[SPI] Engineering Sciences [physics] ,DETECTION CIBLE MOBILE ,SAR PROCESSING ,AEROPORTEE ,SAR IMAGERY ,RADAR ,[PHYS] Physics [physics] ,INTERFEROMETRY ,[SPI]Engineering Sciences [physics] ,RADAR SYSTEM ,GMTI ,AIRBORNE SENSOR - Abstract
With the growing number of operating spatial systems, SAR imagery has become a major topic of research in the remote sensing community. In France, most of the research focuses on the exploitation of satellite SAR images. On the contrary, given the lower availability of such data, the airborne domain concerns a smaller community. This report aims at presenting the specificities of high-resolution airborne radar imagery and their impacts on multi-channel applications.A first part is devoted to a theoretical analysis of airborne SAR processing in its different modalities. The various SAR processing approaches adapted to high resolution are presented from a geometric point of view rather than frequential point of view. Then, the principles of multichannel processing are presented with emphasis on the phenomenology associated with the improvement of the resolution: link between image registration and interferometric phase, behavior of point like scatterers, anisotropic or surfacic backscatters. A second part is dedicated to the impact of real acquisition systems on SAR processing and multichannel applications. Issues related to the radar hardware, the antenna particularities, non-linearities of the trajectories are discussed and illustrated on applications such as calibration of polarimetric data, 3D extraction, ground moving target detection ., Avec la multiplication des systèmes spatiaux, l’imagerie radar fait l’objet de nombreux travaux de recherche. En France, la majorité des travaux se concentre sur l’exploitation des images radar spatiales, de résolution de plus en plus fine. Le domaine aéroporté concerne une communauté plus restreinte étant donnée la moindre disponibilité de telles données. Ce rapport a pour vocation de présenter les spécificités de l’imagerie radar aéroportée haute résolution et d’en comprendre les impacts sur les applications multi-voies.Une première partie est consacrée à l’analyse théorique du traitement SAR aéroporté dans ses différentes modalités. Les diverses approches de traitement SAR adaptés à la haute résolution sont présentées selon un point de vue géométrique plutôt que fréquentiel. Puis, toujours sous ce même angle, les principes des traitements multivoies sont abordés en insistant sur les phénomènes apparaissant avec l’amélioration de la résolution : lien entre recalage d’images et phase interférométrique, comportement des rétrodiffuseurs ponctuels, surfaciques et anisotropes.Une deuxième partie est consacrée à l’étude de l’impact d’un système réel d’acquisition sur le traitement SAR et les applications multivoies. Les problématiques liées à la chaîne radar, aux diagrammes d’antennes, aux trajectoires non linéaires sont abordées.Enfin, différents travaux d’exploitation d’images radar haute résolution aéroportées (calibration de données polarimétriques, extraction du 3D sur les images SAR, détection de cibles mobiles) illustrent le propos.
- Published
- 2018
44. 2D SAR imaging scheme based on compressive sensing.
- Author
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Zhang, Xin, Huang, Puming, and Li, Xiaohui
- Abstract
Synthetic aperture radar (SAR) processing is assumed to start with a demodulated baseband signal and attempt to solve ground reflectivity. An expression of two‐dimensional SAR echo data in the discrete domain is presented. To meet the requirements of the processing power and reduce the storage, a compressive sensing framework is adopted to solve the ground reflectivity. By a small number of signal samplings, the imaging is constructed efficiently and has a higher resolution. Promising results were obtained by several experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
45. Advanced Processing Techniques for GeoSAR Missions
- Author
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Li, Dexin
- Subjects
CoSAR ,GeoSAR ,SAR missions ,SAR processing ,SAR - Published
- 2017
46. Coseismic Ground Displacement after the M w 6.2 Earthquake in NW Croatia Determined from Sentinel-1 and GNSS CORS Data.
- Author
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Bjelotomić Oršulić, Olga, Markovinović, Danko, Varga, Matej, and Bašić, Tomislav
- Subjects
STRIKE-slip faults (Geology) ,EARTHQUAKES ,LINEAR operators ,EARTHQUAKE zones ,REMOTE-sensing images ,EARTHQUAKE aftershocks ,LAND subsidence - Abstract
At the very end of the year 2020, on 29 December, a hazardous earthquake of M
w = 6.2 hit the area of Petrinja and its surroundings, in the NW of Croatia. The earthquake was felt across the area of 400 km, leaving an inconceivable damage in the vicinity of the epicenter, devastated towns and ruined lives. In order to map the spreading of earthquake waves and to determine the coseismic ground displacement after the mainshock, we have analyzed open satellite radar images of Sentinel-1 and the GNSS data from the nearest CORS station related to the epicenter, along with the seismic faults. In this paper, we addressed and mapped the displacement linear surface ruptures detected by the SAR interferometry. The results show the vertical ground displacement to the extent of −12 cm in the southern area and up to 22 cm in the north-western part of a wide area struck by the earthquake impact, related to the epicenter. Subsidence and uplift in a range of ±5 cm over a wider affected area indicate a spatial extent and hazardous impact made by the earthquake. The ground displacement of 30 cm to the West and 40 cm to the East has been identified considering the intersection of Pokupsko and Petrinja strike-slip fault system in the seismic zone of Pannonian basin. Accordingly, we obtained matching results of 5 cm south-easting shift and −3 cm subsidence on Sisak GNSS CROPOS station, addressing the tectonic blocks movement along the activated complex fault system. The results compared with the geology data confirm the existence of two main faults; the Pokupsko and the Petrinja strike-slip faults and interpret the occurrence of secondary post-seismic events over the observed area. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
47. Comment on 'Measurement of Ionospheric TEC in Spaceborne SAR Data'
- Author
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Li Li, Michael Jehle, Yongsheng Zhang, Diannong Liang, and Zhen Dong
- Subjects
Synthetic aperture radar ,Physics ,Autofocus ,total electron content (TEC) ,TEC ,Bandwidth (signal processing) ,0211 other engineering and technologies ,02 engineering and technology ,synthetic aperture radar (SAR) ,Geodesy ,law.invention ,Spaceborne radar ,Ionospheric total electron content ,law ,Chirp ,General Earth and Planetary Sciences ,Ionosphere ,Electrical and Electronic Engineering ,SAR processing ,021101 geological & geomatics engineering ,Remote sensing - Abstract
Two novel approaches for measuring the ionospheric total electron content (TEC) from single-polarized spaceborne SAR data were proposed in the mentioned paper, i.e., the TEC autofocus method and the systematic alternate up/down pulse methodology. The up/down pulse methodology indicates that ionospheric TEC could be estimated using the difference between range-compressed phase distributions of the up and down chirps. However, it can be shown theoretically that the difference between the up and down chirps after compression is not expected. Thus, the estimation of TEC from alternating up versus down chirp combinations might not be feasible.
- Published
- 2016
48. On the Processing of Very High Resolution Spaceborne SAR Data
- Author
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Rolf Scheiber, Marco Schwerdt, Marc Rodriguez-Cassola, Francesco De Zan, Alberto Moreira, Benjamin Bräutigam, Pau Prats-Iraola, Steffen Wollstadt, Andreas Reigber, and Josef Mittermayer
- Subjects
Synthetic aperture radar ,Early-warning radar ,Computer science ,Spotlight SAR ,Fire-control radar ,Space-based radar ,law.invention ,Troposphere ,law ,Radar imaging ,Interferometric synthetic aperture radar ,Chirp ,Electrical and Electronic Engineering ,Radar ,Low-frequency radar ,SAR processing ,Impulse response ,SAR-Technologie ,Remote sensing ,Pulse-Doppler radar ,stop-and-go approximation ,Side looking airborne radar ,Radar lock-on ,Synthetic aperture radar (SAR) ,Continuous-wave radar ,Inverse synthetic aperture radar ,Man-portable radar ,troposphere ,3D radar ,General Earth and Planetary Sciences ,Satelliten-SAR-Systeme ,Radarkonzepte - Abstract
This paper addresses several important aspects that need to be considered for the processing of spaceborne synthetic aperture radar (SAR) data with resolutions in the decimeter range. In particular, it will be shown how the motion of the satellite during the transmission/reception of the chirp signal and the effect of the troposphere deteriorate the impulse response function if not properly considered. Further aspects that have been investigated include the curved orbit, the array pattern for electronically steered antennas, and several considerations within the processing itself. For each aspect, a solution is proposed, and the complete focusing methodology is expounded and validated using simulated point targets and staring spotlight data acquired by TerraSAR-X with 16-cm azimuth resolution and 300-MHz range bandwidth.
- Published
- 2014
49. Efficient Evaluation of Fourier-Based SAR Focusing Kernels
- Author
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Andreas Reigber, Francesco De Zan, Pau Prats-Iraola, Rolf Scheiber, Marc Rodriguez-Cassola, and Paco Lopez-Dekker
- Subjects
Synthetic aperture radar ,Image formation ,SAR spectrum ,Computer science ,spotlight SAR ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Institut für Hochfrequenztechnik und Radarsysteme ,Transfer function ,SAR simulation ,symbols.namesake ,Radar imaging ,Optical transfer function ,Computer vision ,Electrical and Electronic Engineering ,Image sensor ,Point target ,Image resolution ,SAR processing ,Impulse response ,SAR-Technologie ,business.industry ,synthetic aperture radar (SAR) ,Geotechnical Engineering and Engineering Geology ,Bistatic radar ,Fourier transform ,Kernel (statistics) ,symbols ,Artificial intelligence ,business ,Algorithm ,Radarkonzepte - Abstract
This letter addresses the efficient evaluation of Fourier-based kernels for synthetic aperture radar (SAR) image formation. The goal is to evaluate the quality of the focused impulse response function and the residual phase errors of the kernel without having to implement the processor itself nor perform a costly point-target simulation followed by the processing. The proposed methodology is convenient for situations where the assumption of a hyperbolic range history does not hold anymore, and hence, a compact analytic expression of the point target spectrum is not available. Examples where the hyperbolic range history does not apply include very high resolution spaceborne SAR imaging or bistatic SAR imaging. The approach first numerically computes the 2-D spectrum of a point target and then uses the transfer function of the focusing kernel to match it. The spectral support is then computed to adapt the spectrum to the output imaging geometry, so that the impulse response function (IRF) is finally obtained. The proposed approach is valid under the assumption of a large time-bandwidth product, as is usually the case for current air- and spaceborne SAR sensors. The methodology is validated by comparing the matched IRFs with the ones obtained using point-target simulations.
- Published
- 2014
50. MIMO-OFDM signal optimization for SAR imaging radar
- Author
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Eric Pottier, Jean-Yves Baudais, Stephane Meric, Vishal Riche, SCN, Institut d'Électronique et des Technologies du numéRique (IETR), Université de Nantes (UN)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Nantes (UN)-Université de Rennes 1 (UR1), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Université de Nantes (UN)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Nantes (UN)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Nantes Université (NU)-Université de Rennes 1 (UR1), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Nantes Université (NU)-Université de Rennes 1 (UR1)
- Subjects
Synthetic aperture radar ,Computer science ,Orthogonal frequency-division multiplexing ,MIMO ,0211 other engineering and technologies ,Data_CODINGANDINFORMATIONTHEORY ,02 engineering and technology ,MIMO SAR ,law.invention ,Robustness (computer science) ,law ,Radar imaging ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,ComputerSystemsOrganization_SPECIAL-PURPOSEANDAPPLICATION-BASEDSYSTEMS ,Radar ,SAR processing ,Computer Science::Information Theory ,021101 geological & geomatics engineering ,business.industry ,020206 networking & telecommunications ,MIMO-OFDM ,Image quality parameters ,Continuous-wave radar ,Range ambiguity ,Genetic algorithm ,OFDM signals ,Telecommunications ,business ,[SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing - Abstract
International audience; This paper investigates the optimization of the coded orthogonal frequency division multiplexing (OFDM) transmitted signal in a synthetic aperture radar (SAR) context. We propose to design OFDM signals to achieve range ambiguity mitigation. Indeed, range ambiguities are well known to be a limitation for SAR systems which operates with pulsed transmitted signal. The ambiguous reflected signal corresponding to one pulse is then detected when the radar has already transmitted the next pulse. In this paper, we demonstrate that the range ambiguity mitigation is possible by using orthogonal transmitted wave as OFDM pulses. The coded OFDM signal is optimized through genetic optimization procedures based on radar image quality parameters. Moreover, we propose to design a multiple-input multiple-output (MIMO) configuration to enhance the noise robustness of a radar system and this configuration is mainly efficient in the case of using orthogonal waves as OFDM pulses. The results we obtain show that OFDM signals outperform conventional radar chirps for range ambiguity suppression and for robustness enhancement in 2×2 MIMO configuration.
- Published
- 2016
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