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  • 51.
    Sievert, Thomas
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Rasch, Joel
    Molflow, Gothenburg, SWE.
    Carlström, Anders
    RUAG Space AB, SWE.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Analysis of reflections in GNSS radio occultation measurements using the phase matching amplitude2018Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 11, nr 1, s. 569-580Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is well-known that in the presence of super-refractive layers in the lower-tropospheric inversion of GNSSradio occultation (RO) measurements using the Abel trans-form yields biased refractivity profiles. As such it is problem-atic to reconstruct the true refractivity from the RO signal.Additional information about this lower region of the atmo-sphere might be embedded in reflected parts of the signal. Toretrieve the bending angle, the phase matching operator canbe used. This operator produces a complex function of theimpact parameter, and from its phase we can calculate thebending angle. Instead of looking at the phase, in this paperwe focus on the function’s amplitude. The results in this pa-per show that the signatures of surface reflections in GNSSRO measurements can be significantly enhanced when usingthe phase matching method by processing only an appropri-ately selected segment of the received signal. This signatureenhancement is demonstrated by simulations and confirmedwith 10 hand-picked MetOp-A occultations with reflectedcomponents. To validate that these events show signs of re-flections, radio holographic images are generated. Our resultssuggest that the phase matching amplitude carries informa-tion that can improve the interpretation of radio occultationmeasurements in the lower troposphere.

  • 52.
    Sievert, Thomas
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Rasch, Joel
    Molflow, SWE.
    Carlström, Anders
    RUAG Space AB, SWE.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Vu, Viet Thuy
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Comparing reflection signatures in radio occultation measurements using the full spectrum inversion and phase matching methods2018Inngår i: PROCEEDINGS VOLUME 10786; Remote Sensing of Clouds and the Atmosphere XXIII / [ed] Comeron A.,Kassianov E.,Picard R.H.,Schafer K.,Weber K., SPIE - International Society for Optical Engineering, 2018, artikkel-id 107860AKonferansepaper (Fagfellevurdert)
    Abstract [en]

    Global Navigation Satellite System Radio Occultation (GNSS-RO) is an important technique used to sound the Earth's atmosphere and provide data products to numerical weather prediction (NWP) systems as well as toclimate research. It provides a high vertical resolution and SI-traceability that are both valuable complements toother Earth observation systems. In addition to direct components refracted in the atmosphere, many received RO signals contain reflected components thanks to the specular and relatively smooth characteristics of the ocean. These reflected components can interfere the retrieval of the direct part of the signal, and can also contain meteorological information of their own, e.g., information about the refractivity at the Earth's surface. While the conventional method to detect such reflections is by using radio-holographic methods, it has been shown that it is possible to see reflections using wave optics inversion, specically while inspecting the amplitude of the output of phase matching (PM). The primary objective of this paper is to analyze the appearance of these reflections in the amplitude output from another wave optics algorithm, namely the much faster full spectrum inversion (FSI). PM and FSI are closely related algorithms - they both use the method of stationary phase to derive the bending angle from a measured signal. We apply our own implementation of FSI to the same GNSS-RO measurements that PM was previously applied to and show that the amplitudes of the outputs again indicate reflection in the surface of the ocean. Our results show that the amplitudes output from the FSI and PM algorithms are practically identical and that the reflection signatures thus appear equally well.

  • 53.
    Sjögren, Thomas
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Vu, Viet
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Wang, Feng
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Murdin, Daniel
    Gustavsson, Anders
    Ulander, Lars
    Forest Clutter Suppression for Moving Target Detection in UHF Dual Channel SAR2013Konferansepaper (Fagfellevurdert)
  • 54.
    Sjögren, Thomas
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Vu, Viet
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Wang, Feng
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Murdin, Daniel
    Gustavsson, Anders
    Ulander, Lars
    Suppression of Clutter in Multichannel SAR GMTI2014Inngår i: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 52, nr 7, s. 4005-4013Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, results of moving target detection in multichannel UHF-band Synthetic Aperture Radar (SAR) data are shown. The clutter suppression is done using Finite Impulse Response (FIR) filtering of multichannel SAR in combination with a 2-stage Fast Backprojection (FBP) algorithm to focus the moving target using relative speed. The FIR filter coefficients are chosen with the use of STAP filtering. Two parameters are used for target focusing, target speed in range and in azimuth. When the target is focused, both speed parameters of the target are found. In the experimental results, two channels were used in order to suppress clutter. In the resulting SAR images it is obvious that very strong scatterers and the forest areas have been suppressed in comparison to the moving target in the image scene. The gain obtained can be measured using SCNR gain, which is about 19dB. Another way to measure signal processing gain is the ability to suppress the strongest reflecting object in the SAR scene. The gain of target in relation to this object is 25dB. This shows that using UHF-band SAR GMTI for suppressing forest and increasing the target signal can work.

  • 55. Sjögren, Thomas
    et al.
    Vu, Viet Thuy
    Pettersson, Mats
    2D apodization in UWB SAR using linear filtering2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, an investigation is made on how sidelobes can be suppressed in ultrawideband-ultrawidebeam (UWB) Synthetic Aperture Radar (SAR) using apodization. Due to the special properties of UWB SAR such as very wide integration angle and very large relative bandwidth, the support for the spectrum of a SAR image differs distinctively from a rectangle, which is the normal approximation in narrowband-narrowbeam (NB) SAR. The proposal in the paper is to apply non-separable windows to the spectrum, in order to suppress sidelobes. Non-separable windows are shown to give less broadening of mainlobe while maintaining the same suppression of sidelobes in comparison to separable windows. In the comparison, parameters for three different SAR systems are used.

  • 56. Sjögren, Thomas
    et al.
    Vu, Viet Thuy
    Pettersson, Mats
    A Comparative Study of the Polar Version with the Subimage Version of Fast Factorized Backprojection in UWB SAR2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a comparative study of the polar and the subimage based variants of the time domain SAR algorithm Fast Factorized Backprojection. The difference between the two variants with regard to the phase error, which causes defocusing in the image, is investigated. The difference between the algorithms in interpolation between stages is also discussed. To investigate the sidelobes in azimuth, the paper gives simulation results for a low frequency UWB SAR system for both algorithms. How the algorithms differ with regard to amount of beams and length of beams is also discussed.

  • 57. Sjögren, Thomas
    et al.
    Vu, Viet Thuy
    Pettersson, Mats
    Moving Target Refocusing Algorithm for Synthetic Aperture Radar Images2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the area of SAR imaging, it is of interest to be able to focus moving targets. In this paper, an algorithm for moving target focusing is presented. The algorithm is able to refocus a smeared moving target in a SAR image processed at one relative speed to the correct one.. The algorithm works in the frequency domain and is based on the Range Migration algorithm. The refocusing can be made on the whole SAR image or small sub images corresponding to physical areas of interest for the end user. By applying the algorithm to a small image, the computational cost is greatly reduced compared with using the full SAR image. The performance is illustrated by applying the algorithm to simulated SAR data according to the parameters for the LORA system.

  • 58. Sjögren, Thomas
    et al.
    Vu, Viet Thuy
    Pettersson, Mats
    Moving Target Relative Speed Estimation in the Presence of Strong Stationary Surrounding Using a Single Antenna UWB SAR System2008Konferansepaper (Fagfellevurdert)
  • 59. Sjögren, Thomas
    et al.
    Vu, Viet Thuy
    Pettersson, Mats
    Zepernick, Hans-Jürgen
    Gustavsson, Anders
    Speed Estimation Experiments for Ground Moving Targets in Low Frequency UWB2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an iterative method to estimate the Normalised Relative Speed (NRS) of ground moving targets in Ultra Wideband (UWB) wide beam Synthetic Aperture Radar (SAR) using one antenna. The number of iterations depends on the separation between processed NRS and true target NRS. The NRS estimate is based on a chirp rate estimator in azimuth direction of the SAR image. The paper derives an analytical expression of the azimuth phase information based on the moving target NRS and the NRS used in the image formation. The method has been tested on real data from the CARABAS-II SAR system showing good results.

  • 60.
    Sjögren, Tomas
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Vu, Viet
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Gustavsson, Anders
    Ulander, Lars
    Moving Target Relative Speed Estimation and Refocusing in Synthetic Aperture Radar Images2012Inngår i: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 48, nr 3, s. 2426-2436Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, a method for moving target relative speed estimation and refocusing based on synthetic aperture radar (SAR) images is derived and tested in simulation and on real data with good results. Furthermore, an approach on how to combine the estimation method with the refocusing method is introduced. The estimation is based on a chirp estimator that operates in the SAR image and the refocusing of the moving target is performed locally using subimages. Focusing of the moving target is achieved in the frequency domain by phase compensation, and therefore makes it even possible to handle large range cell migration in the SAR subimages. The proposed approach is tested in a simulation and also on real ultrawideband (UWB) SAR data with very good results. The estimation method works especially well in connection with low frequency (LF) UWB SAR, where the clutter is well focused and the phase of the smeared moving target signal becomes less distorted. The main limitation of the approach is target accelerations where the distortion increases with the integration time.

  • 61. Tegborg, Viktoria
    et al.
    Pettersson, Mats
    Claesson, Ingvar
    Experimental results of passive imaging of moving continuous broadband sound sources within a sensor field2011Inngår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 36, nr 1, s. 26-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sparsely distributed sensors or sparse arrays can be associated with high positional accuracy and capability for large area surveillance. This paper shows, both through simulations and with real measurement data, that sparse sensor systems can be used to accomplish high-performance underwater surveillance. The paper focuses on measurement setups with several passive single hydrophones placed hundreds of meters apart in a water depth of dozen of meters. By such a setup, a sound source is more likely to move inside the array, and thus near-field processing can be considered. The sensor pairs will also be located in different directions in relation to the sound source. These two prerequisites give the possibilities to high spatial resolution. Images of the coherent sound activity for different sensor pairs are formed, and every sensor pair map is summarized into a resulting map. In this way, an arbitrary number of sound sources of a target can be resolved. Good correlation results are shown even when the sound sources are at the same distance as the baseline of the sensor pairs. This is achieved by Doppler compensating for target movement and also by whitening of the cross spectra. The analyses of the measurements also show that baseline-dependent bandwidth can improve the results. In this paper, it is indicated from experimental data that two propeller sound sources could be resolved, and in another measurement setup, the engine could be separated from the propellers.

  • 62.
    Thomas, Sjögren
    et al.
    Totalforsvarets forskningsinstitut, SWE.
    Vu, Viet Thuy
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Experimental result for SAR GMTI using monostatic pursuit mode of TerraSAR-X and TanDEM-X on staring spotlight images2016Inngår i: Proceedings of EUSAR 2016: 11th European Conference on Synthetic Aperture Radar, IEEE, 2016, s. 207-210, artikkel-id 7559278Konferansepaper (Fagfellevurdert)
    Abstract [en]

    TerraSAR-X and TanDEM-X is able to fly in monostatic pursuit mode, a formation with the satellites in identic orbit displaced in along-Track of a distance corresponding to 10 s delay. Such formation gives e.g. The ability to detect very slow targets or targets moving only between measurements. This can be performed using Change Detection (CD) and/or the Detection of Moving Targets by Focusing (DMTF) technique. A combination of DMTF and CD is promising. To investigate the applicability of the methods for moving target detection, an experiment was performed with TerraSAR-X and TanDEM-X in monostatic pursuit mode and several deployed targets. © VDE VERLAG GMBH · Berlin · Offenbach.

  • 63.
    Viet Thuy, Vu
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Mats, Pettersson
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Thomas, Sjögren
    Swedish Defence Research Agency.
    Monostatic pursuit mode for SAR GMTI based on change detection methods2016Konferansepaper (Fagfellevurdert)
  • 64.
    Vu, Viet
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Nehru, Dheeraj
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    An Experimental Ground-based SAR System for Studying SAR Fundamentals2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper introduces a simple experimental groundbased SAR system for studying SAR fundamentals. The SAR system is developed on a vector network analyzer (VNA), for example Agilent E5071C, with some useful built-in functions such as transform and gating. The procedure of acquiring the data by using the SAR system is presented in details. The acquired empirical data is also used to reconstruct the illuminated scene. The possibilities to use the SAR system to support SAR research topics are also discussed in this paper.

  • 65.
    Vu, Viet
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Another possibility to focus moving targets by normalized relative speed in UWB SAR2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents another possibility to focus moving targets using normalized relative speed (NRS). Similar to the currently used focusing approach, the focusing approach proposed in this paper aims at the ultrawideband and ultrawidebeam synthetic aperture radar systems (UWB SAR) like CARABAS-II. The proposal is shown to overcome the shortcomings of the original focusing approach and can be extended to more complicated cases, for example bistatic SAR.

  • 66.
    Vu, Viet
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    The Capability of Time- And Frequency-domain Algorithms for Bistatic SAR Processing2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents a study of the capability of time- And frequency-domain algorithms for bistatic SAR processing. Two typical algorithms, Bistatic Fast Backprojection (BiFBP) and Bistatic Range Doppler (BiRDA), which are both available for general bistatic geometry, are selected as the examples of time- And frequency-domain algorithms in this study. Their capability is evaluated based on some criteria such as processing time required by the algorithms to reconstruct SAR images from bistatic SAR data and the quality assessments of those SAR images.

  • 67.
    Vu, Viet
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Two-Dimensional Spectrum for BiSAR Derivation Based on Lagrange Inversion Theorem2014Inngår i: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 11, nr 7, s. 1210-1214Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A 2-D spectrum for bistatic synthetic aperture radar is derived in this letter. The derivation is based on the commonly used mathematic principles such as themethod of stationary phase and the Fourier transform and the Lagrange inversion theorem in order to find the point of stationary phase in the method of stationary phase. Using the Lagrange inversion theorem allows minimizing the initial assumptions or the initial approximations. The derived 2-D spectrum is compared with the commonly used 2-D spectrum to verify it and illustrate its accuracy.

  • 68.
    Vu, Viet T.
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Machado, Renato
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Pettersson, Mats I.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Dammert, Patrik
    Saab Elect Defense Syst, S-41289 Gothenburg, Sweden..
    Hellsten, Hans
    Saab Elect Defense Syst, S-41289 Gothenburg, Sweden..
    SAR image statistics and adaptive signal processing for change detection2015Inngår i: ALGORITHMS FOR SYNTHETIC APERTURE RADAR IMAGERY XXII, 2015, artikkel-id 947509Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents investigations on SAR image statistics and adaptive signal processing for change detection. The investigations show that the amplitude distributions of SAR images with possibly detected changes, that is retrieved with a linear subtraction operator, can approximately be represented by the probability density function of the Gaussian or normal distribution. This allows emerging the idea to use the available adaptive signal processing techniques for change detection. The experiments indicate the promising change detection results obtained with an adaptive line enhancer, one of the adaptive signal processing technique. The experiments are conducted on the data collected by CARABAS, a UWB low frequency SAR system.

  • 69.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Alves, Dimas
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Palm, Brna
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Dammert, Patrik
    Saab, SWE.
    Hellsten, Hans
    Saab, SWE.
    A detector for wavelength resolution SAR incoherent change detection2019Inngår i: 2019 IEEE Radar Conference, RadarConf 2019, Institute of Electrical and Electronics Engineers Inc. , 2019, artikkel-id 8835574Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper introduces an effective detector for wavelength-resolution SAR incoherent change detection. The detector is derived from Bayes' theorem. The input of the detector is the differences between surveillance and reference magnitude images simply obtained by a subtraction while the output is a summary of the detected changes. The proposed detector is tested with 24 CARABAS images that were obtained from the measurement campaign in northern Sweden in 2002. The testing results show that the detector can provide a high average detection probability, e.g., about 96%, with a very low false alarm rate, e.g., only 0.35 per square kilometer. © 2019 IEEE.

  • 70.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Gomes, Natanael Rodrigues
    Universidade Federal de Santa Maria, BRA.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Dämmert, Patrik
    Saab Surveillance, SWE.
    Hellsten, Hans
    Saab Surveillance, SWE.
    Bivariate Gamma Distribution for Wavelength-Resolution SAR Change Detection2019Inngår i: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 57, nr 1, s. 473-481Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A gamma probability density function (pdf) is shown to be an alternative to model the distribution of the magnitudes of high-resolution, i.e., wavelength-resolution, synthetic aperture radar (SAR) images. As investigated in this paper, it is more appropriate and more realistic statistical in comparison with, e.g., Rayleigh. A bivariate gamma pdf is considered for developing a statistical hypothesis test for wavelength-resolution incoherent SAR change detection. The practical issues in implementation of statistical hypothesis test, such as assumptions on target magnitudes, estimations for scale and shape parameters, and implementation of modified Bessel function, are addressed. This paper also proposes a simple processing scheme for incoherent change detection to validate the proposed statistical hypothesis test. The proposal was experimented with 24 CARABAS data sets. With an average detection probability of 96%, the false alarm rate is only 0.47 per square kilometer. IEEE

  • 71.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Nehru, Dheeraj
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Sjögren, Thomas
    SAR Resolution Enhancement with Circular Aperture in Theory and Empirical Scenario2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    SAR systems synthesizing circular apertures have been shown to result in better spatial resolutions than the ones synthesizing linear apertures. The paper presents an investigation about the enhancement of SAR spatial resolutions with the use of circular aperture. A comparison between the spatial resolutions obtained with a SAR system synthesizing a circular aperture and with the same SAR system synthesizing a linear aperture is therefore carried out. The studying results are verified by the experimental SAR data set provided by the experimental ground-based SAR system of Blekinge Institute of Technology (BTH GB-SAR).

  • 72.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Derivation of Bistatic SAR Resolution Equations Based on Backprojection2018Inngår i: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 15, nr 5, s. 694-698Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This letter introduces ground-range and cross-range resolution equations for the side-looking bistatic synthetic aperture radar (SAR). The derivation is based on the backprojection integral and the method of stationary phase. The ground-range and cross-range resolution equations are provided in closed form, making them easy for calculation. They are, therefore, helpful for bistatic SAR system development. The derived ground-range and cross-range resolution equations are validated with the bistatic data simulated mainly using the parameters of the LORA system. IEEE

  • 73.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Doppler and Cross-range Resolutions in Bistatic Forward-looking SAR Imaging2015Inngår i: 2015 IEEE INTERNATIONAL RADAR CONFERENCE (RADARCON), IEEE Computer Society, 2015, s. 72-76Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Left/right ambiguity and low Doppler resolution are severe problems for monostatic forward-looking SAR imaging. Among approaches for the problems, using bistatic SAR is very promising. The left/right ambiguity in bistatic forwardlooking SAR has been investigated in detail recently whereas an appropriate study for enhancing bistatic forward-looking SAR Doppler resolution is still desired. A research on Doppler resolution and then cross-range resolution in bistatic forward-looking SAR is therefore presented in this paper. The research is based on the use of the gradient. Several recommendations which allow maximizing Doppler resolution and cross-range in bistatic forward-looking SAR imaging are provided.

  • 74.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Fast Backprojection Algorithms Based on Subapertures and Local Polar Coordinates for General Bistatic Airborne SAR Systems2016Inngår i: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 54, nr 5, s. 2706-2712Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper introduces a bistatic fast backprojection synthetic aperture radar (SAR) algorithm that is available for different bistatic geometries. The proposed algorithm is tested with the bistatic CARABAS-like data, and the results indicate that the algorithm is a good candidate for bistatic SAR data processing. The image quality measurements are quite similar to the referenced values obtained with the bistatic global backprojection algorithm. That is, the peak sidelobe ratio (PSLR) is -13.7 dB in comparison to the referenced PSLR of -13.8 dB. The half-power beamwidths (HPBWs) measured on the cuts in x and y and the direction where the peak sidelobes locate are 2.8, 3.7, and 3.5 m, respectively, which are approximate to the referenced HPBWs. The small differences in the measured results mainly come from the interpolation step of the algorithm.

  • 75.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Ground Moving Target Detection and Estimation By Using Dual Speed SAR Platform2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper proposes a ground moving target detection and estimation method aiming at Ultra Wide Band and -Beam (UWB) Synthetic Aperture Radar (SAR) systems. The method is developed on the moving target detection by focusing technique and requires a SAR system flying with two different speeds during the integration time. The method allows us to detect ground moving target, even hidden by clutter, and to estimate the target parameters, i.e. speed and direction of motion. The accuracy of the estimations depends strongly on the computational cost and can therefore be controlled. The proposal is tested with the simulated CARABAS data.

  • 76.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Nyquist Sampling Requirements for Polar Grids in Bistatic Time-Domain Algorithms2015Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, nr 2, s. 457-465Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper presents a derivation of Nyquist sampling requirements for the polar grids in some bistatic time-domain algorithms. The derivation is based on an airborne bistatic system with general bistatic geometry. The Nyquist sampling requirements are shown to be the functions of operating radar frequency, transmitter and receiver subaperture lengths, and bistatic geometry. How to decide the Nyquist sampling requirements for different bistatic geometries and the relationship between the Nyquist sampling requirements in the monostatic and bistatic cases are also addressed in the paper. The derived Nyquist sampling requirements is examined with the bistatic CARABAS-II like data.

  • 77.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    On Bistatic Forward-looking SAR Imaging2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Left/right ambiguity and low angular (azimuth) resolution are severe problems for monostatic forward-looking SAR imaging. It is strongly believed that these technical issues can definitely be solved with bistatic forward-looking SAR. The analysis presented in this paper points out that the left/right ambiguity problem still exits. However, an appropriate selection of the position of bistatic base line and antenna beamwidth allows us to conceal it. The paper also gives some recommendations which can be considred for the forward-looking SAR imaging.

  • 78.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Range migration algorithm for bistatic SAR2018Inngår i: IEEE Radar Conference, (RadarConf 2018), Institute of Electrical and Electronics Engineers Inc. , 2018, s. 665-669Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper introduces a Range Migration algorithm for bistatic SAR data processing. The algorithm is developed on the available function representing the two-dimension Fourier transform of the bistatic SAR data and relationship between radar signal frequency and wave-numbers for bistatic SAR or the ω - k relationship. The algorithm is tested with the simulations using different SAR geometries for validation. Some inherit limits of the developed Range Migration algorithm and the possible solutions are also discussed in the paper. © 2018 IEEE.

  • 79.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Björklund, Svante
    A method to implement SAR slow-time stap in beamforming stage of fast backprojection algorithm2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a method to implement SAR slow-time space time adaptive processing (STAP) in the beamforming stage of the fast backprojection algorithm. This method is different from the recently published method where the SAR fast-time STAP is implemented after the beamforming stage for detection and then imaging. As a common SAR STAP method, the method proposed in this paper can be used for ground moving target indication (GMTI) and reconstruction of the image of the detected moving targets. The paper also presents some simulation results in order to illustrate the proposed method.

  • 80.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Dämmert, Patrik
    SAAB Surveillance, SWE.
    Hellsten, Hans
    SAAB Surveillance, SWE.
    Two-Dimensional Data Conversion for One-Dimensional Adaptive Noise Canceler in Low Frequency SAR Change Detection2018Inngår i: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 54, nr 5, s. 2611-2618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One-dimensional (1-D) adaptive noise canceler (ANC) has been used for false alarm reduction in low frequency SAR change detection. The paper presents possibilities to process two-dimensional (2-D) data by an 1-D ANC. Beside concatenating the rows of 2-D data in a matrix form to convert it to 1-D data in a vector form, two conversion approaches are considered: concatenating the columns of 2-D data and local concatenation, i.e., the conversion to 1-D is performed locally on each block of the 2-D data. A ground object can occupy more than one row and/or more than one column of 2-D data. In addition, the properties in cross-range and range of an image are not the same. Thus, different conversion approaches may lead to different performance of an 1-D ANC and hence different change detection results. Among the considered approaches, the local concatenating approach is shown to provide slightly better performance in terms of probability of detection and false alarm rate. IEEE

  • 81.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Gomes, Natanael
    Universidade Federal de Santa Maria, BRA.
    Dammert, Patrik
    Saab Electronic Defense Systems, SWE.
    Hellsten, Hans
    Saab Electronic Defense Systems, SWE.
    Wavelength-resolution SAR change detection with constant false alarm rate2017Inngår i: 2017 IEEE Radar Conference, RadarConf 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, s. 1504-1508Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper introduces an incoherent change detection algorithm with constant false alarm rate (CFAR). The algorithm is based on a CFAR detector that preceded with an adaptive noise smoothing filter while the input of the filter is preliminary changes retrieved from a subtraction of surveillance SAR image to reference SAR image. The algorithm is tested with 24 data sets provided by CARABAS. The average probability of detection calculated for 1200 deployed vehicles is up to 96% while the false alarm rate calculated for an area of 288 square kilometers is only 0.15 per square kilometer. In our test, the algorithm did not require a longer processing time than other wavelength-resolution SAR change detection algorithms. Based on these evaluations, the introduced algorithm is seen to be effective. © 2017 IEEE.

  • 82.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Gomes, Natanael Rodrigues
    Federal University of Santa Maria, BRA.
    Stability in Sar Change Detection Results Using Bivariate Rayleigh Distribution for Statistical Hypothesis Test2019Inngår i: International Geoscience and Remote Sensing Symposium (IGARSS), Institute of Electrical and Electronics Engineers Inc. , 2019, s. 37-40, artikkel-id 8898728Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A statistical hypothesis test for wavelength-resolution SAR change detection can be derived with the bivariate distributions such as Rayleigh, Gamma and K. The paper investigates the stability of change detection results obtained with a statistical hypothesis test using bivariate Rayleigh distribution. Some practical issues concerning the implementation of the statistical hypothesis test such as scale parameter estimation, target magnitude assumptions and Bessel function calculation are also addressed. The statistical hypothesis test using bi-variate Rayleigh distribution are experimented with the data set containing 24 CARABAS II images. It is shown that beside the simplicity and efficiency, a statistical hypothesis test using bivariate Rayleigh distribution can provide very stable change detection results. © 2019 IEEE.

  • 83.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Machado, Renato
    Federal University of Santa Maria, BRA.
    Dammert, Patrik
    Saab Electronic Defense Systems, SWE.
    Hellsten, Hans
    Saab Electronic Defense Systems, SWE.
    False Alarm Reduction in Wavelength-Resolution SAR Change Detection Using Adaptive Noise Canceler2017Inngår i: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 55, nr 1, s. 591-599Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper introduces a method to reduce false alarms in wavelength-resolution synthetic aperture radar (SAR) change detection and aims at very high frequency-band systems like the Coherent All Radio Band System (CARABAS). The false alarms are usually caused by the elongated structures, such as power lines and fences, which stand out from the background. The responses of elongated structures are sensitive to flight path. The introduced method aims at minimizing the false alarms caused by the elongated structures and is based on the well-known adaptive processing mechanism, i.e., the so-called adaptive noise canceler (ANC) where a separate reference signal is required. The changes between measurements are considered by the input signal of ANC while the separate reference signal comes from the measurements without change. Hence, the method requires three SAR images associated with three measurements, with no changes between two of them. The reference data for the study are provided by CARABAS. The experimental results indicate that the method can reduce false alarms significantly and provide high probability of detection (≥98%). The experimental results also show that the method still works well even in the case where the flight tracks of the SAR system in the change detection measurements are slightly different.

  • 84.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Sjögren, Thomas
    Swedish Defence Research Agency, Linköping, Sweden.
    Experimental results on focusing moving targets in TerraSAR-X and TanDEM-X images2016Inngår i: IEEE Radar Conference, IEEE Press, 2016, s. 874-878Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Moving targets appear in TerraSAR-X and TanDEM-X images in the form of elliptic or hyperbolic curves but they can be approximated to be lines. We present here the experimental results on refocusing moving targets directly in TerraSAR-X and TanDEM-X images. The refocusing method is developed from the Range Migration algorithm and the concept of normalized relative speed. The experimental results show that the target in TerraSAR-X and TanDEM-X images is well focused to the original shape. Motion parameters of the moving target can be further estimated thank to the pursuit mode of TerraSAR-X and TanDEM-X.

  • 85.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Sjögren, Thomas
    Totalforsvarets forskningsinstitut, Stockholm, Sweden .
    Local detection of moving target by focusing in SAR images2016Inngår i: IEEE Radar Conference, IEEE Press, 2016, s. 827-832Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present here a moving target detection method so-called local detection of moving target by focusing. The term local implies that the method only works with areas of interest but not whole SAR scene whereas the term focusing indicates that the method is based on the concept of relative movement. The mathematical background of the method is presented in details. The introduced method is then examined with simulated and experimental SAR data to evaluate the method as well as to show the practicality of the method. The reference SAR system for this study is CARABAS, an airborne UWB low frequency SAR system. The method shows a number of advantages in comparison to the original version.

  • 86.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Sjögren, Thomas
    Two-Dimensional Spectrum for BiSAR Derivation Based on Lagrange Inversion Theorem2014Inngår i: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 11, nr 7, s. 1210-1214Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A 2-D spectrum for bistatic synthetic aperture radar is derived in this letter. The derivation is based on the commonly used mathematic principles such as themethod of stationary phase and the Fourier transform and the Lagrange inversion theorem in order to find the point of stationary phase in the method of stationary phase. Using the Lagrange inversion theorem allows minimizing the initial assumptions or the initial approximations. The derived 2-D spectrum is compared with the commonly

  • 87.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Sjögren, Thomas
    Gustavsson, Anders
    Swedish Def Res Agcy, SWE.
    A hybrid GMTI method for reliable detec ion results in SAR images2018Inngår i: PROCEEDINGS OF 2018 2ND INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN SIGNAL PROCESSING, TELECOMMUNICATIONS & COMPUTING (SIGTELCOM 2018) / [ed] Bao, VNQ Duy, TT, IEEE , 2018, s. 73-78Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stand-alone synthetic aperture radar (SAR) ground moving target indication (GNITI) methods have both advantages and disadvantages. This paper introduces a hybrid SAR GMTI method that is based on two well-known methods: space time adaptive processing (STAP) and moving target detection by focusing (MTDF). The input of the proposed hybrid method is two time separated complex radar images. The output is detected ground moving targets, the target normalized relative speeds (NRS), and focused images of the detected targets. In the paper, we provide the mathematical background behind the hybrid SAR GMTI method in details. We also provide some experimental results for validating the proposed method. The data for the experiments was acquired in early 2015 by TanDEMX and TerraSAR-X operating in monostatic pursuit mode. The ground scene where the measurements were conducted is around Mantorp, west of Linkoping, Sweden.

  • 88.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Sjögren, Thomas
    Gustavsson, Anders
    Totalförsvarets forskningsinstitut, SWE.
    A hybrid GMTI method for reliable detection results in SAR images2018Inngår i: Proceedings - 2018 2nd International Conference on Recent Advances in Signal Processing, Telecommunications and Computing, SIGTELCOM 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, s. 73-78Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stand-alone synthetic aperture radar (SAR) ground moving target indication (GMTI) methods have both advantages and disadvantages. This paper introduces a hybrid SAR GMTI method that is based on two well-known methods: space time adaptive processing (STAP) and moving target detection by focusing (MTDF). The input of the proposed hybrid method is two time separated complex radar images. The output is detected ground moving targets, the target normalized relative speeds (NRS), and focused images of the detected targets. In the paper, we provide the mathematical background behind the hybrid SAR GMTI method in details. We also provide some experimental results for validating the proposed method. The data for the experiments was acquired in early 2015 by TanDEM-X and TerraSAR-X operating in monostatic pursuit mode. The ground scene where the measurements were conducted is around Mantorp, west of Linköping, Sweden. © 2018 IEEE.

  • 89.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap. Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling. Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för matematik och naturvetenskap. Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    thomas, Sjögren
    Swedish Defence Research Agency, SWE.
    Moving Target Focusing in SAR Image with Known Normalized Relative Speed2017Inngår i: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 53, nr 2, s. 854-861Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the moving target focusing method, whichallows focusing moving targets in complex synthetic aperture radar(SAR) images without raw data. The method is developed on the rangemigration algorithm, where focusing moving target is an interpolationstep in the wave domain. The simulated results are provided in thepaper to illustrate the proposed method whereas the experimentalresults show its practicality. The method can be flexibly applied fromsmall area to the whole SAR scene.

  • 90.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjogren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Minardi, Michael
    Studying Csar Systems Using Irf-Csar2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, Impulse Response Function in Circular Synthetic Aperture Radar Imaging (IRF-CSAR), which is a special version of Impulse Response Function in Ultrawideband-Ultrawidebeam Synthetic Aperture Radar Imaging (IRF-USAR), is presented and shown to be valid for representing the CSAR image of a point-like scatterer. IRF-CSAR can therefore be used in studying different CSAR systems such as predicting the pattern of a point-like scatterer illuminated by a CSAR system, estimating resolution achieved by that system. Applying IRF-CSAR to define the image quality assessments for CSAR is also presented in the paper.

  • 91. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    A comparison between Fast Factorized Backprojection and frequency-domain algorithms in UWB low frequency SAR2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Two frequency-domain algorithms Chirp Scaling (CS) with the advantage of simplification and Range Migration (RM) with the advantage of accuracy are candidates for a comparative study to the time-domain algorithm Fast Factorized Backprojection (FFBP) with reference to a UWB system are presented in this paper. The comparison is based on UWB SAR image quality measurements such as spatial resolution, Integrated Sidelobe Ratio (ISLR), Peak Sidelobe Ratio (PSLR) and processing time connected to computational cost. The simulated SAR data, which is used in this study, is based on the parameters of the airborne UWB low frequency CARABAS-II system.

  • 92. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Fast backprojection algorithm for UWB bistatic SAR2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper introduces an algorithm for Ultrawideband Ultrawidebeam (UWB) bistatic Synthetic Aperture Radar (SAR). The algorithm works in time-domain and therefore inherits time-domain characteristics such as unlimited scene size, local processing and manageable motion compensation. The proposed algorithm is not limited by any configuration of bistatic SAR. The algorithm processes the UWB bistatic SAR data on a subaperture and subimage basis. This means, instead of backprojecting directly the SAR data to a ground image plane, the algorithm handles the data in two stages: beam forming and local backprojection. The algorithm is named Bistatic Fast Backprojection (BiFBP) and has been tested successfully with the simulated UWB bistatic SAR data.

  • 93. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Fast Detection of Moving Targets by Focusing in Multi-Channel Ultra-Wideband SAR2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Long processing time and, in certain cases, restricted ability to detect moving targets are seen as the shortcomings of the moving target detection by focusing technique. The detection ability reduces significantly when Normalized Relative Speeds (NRS) with respect to the speed of the platform are approximated or equal to one. This paper propose solutions for such problems. Local Backprojection (LBP) replaces Global Backprojection (GBP) in the focusing approach of the detection method to save the processing time and a space-time processing technique, namely Displaced Phase Center Antenna (DPCA) is used to pre-process multi-channel SAR data to strengthen detection ability. Simulation results demonstrates a fast- and reliable detection achieved with these proposals.

  • 94. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Fast detection of moving targets by focusing in Ultra-wideband SAR2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Moving target detection in Ultra-Wideband (UWB) SAR is associated with long integration time and has to handle azimuth focusing for reliable detection. This paper presents the theory and simulation results of the Fast Detection of Moving Targets by Focusing method (FDMTF) which is understood as the Detection of Moving Targets by Focusing method (DMTF) incorporating fast time-domain algorithms in the process. Two fast time-domain algorithms Fast Backprojection (PBP) and Fast Factorized Backprojection (FFBP) are considered. The results show that FDMTF performs very efficiently and still retains the ability of detection.

  • 95. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Fast factorized backprojection algorithm for UWB SAR image reconstruction2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The fast factorized backprojection for bistatic SAR algorithm (BiFFBP), which processes the bistatic SAR data in more than one beam forming stage, is presented in this paper. The algorithm is developed on the bistatic fast backprojection algorithm SAR (BiFBP) and inherits time-domain characteristics such as unlimited scene size, real time processing, local processing, manageable motion compensation, and large range migration handling. Also, the algorithm works well with different kinds of bistatic configuration. For these reason, it is very suitable for UWB bistatic SAR processing. The proposed algorithm is tested successfully with simulated UWB bistatic SAR data.

  • 96.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Fast Time-Domain Algorithms for UWB Bistatic SAR Processing2013Inngår i: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 49, nr 3, s. 1982-1994Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two fast time-domain algorithms are introduced for ultrawideband-ultrawidebeam (UWB) bistatic synthetic aperture radar (SAR) processing; they are bistatic fast backprojection (BiFBP) and bistatic fast factorized backprojection (BiFFBP). Both algorithms process radar echoes on a subaperture and subimage basis in order to minimize processing time. They are shown to work with any configuration of bistatic SAR. They also own time-domain characteristics, which are essential for UWB radar signal processing. BiFBP and BiFFBP are experimented successfully on the CARABAS-II simulated data.

  • 97.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Ground Moving Target Detection and Estimation with Different Sar Linear Flight Tracks2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper proposes a groundmoving target detection and estimation method aiming at UltraWide Band and -Beam (UWB) Synthetic Aperture Radar (SAR) systems. The method is developed on the moving target detection by focusing technique and requires a SAR system flying with two different linear flight tracks. The method allows us to detect ground moving target, even hidden by clutter, and to estimate the target parameters such as speed and direction of motion. The accuracy of the estimations depends strongly on the computational cost and can therefore be controlled.

  • 98. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Integrating Space-time Processing Into Time-Domain Backprojection Process to Detect and Imaging Moving Objects2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper discusses a possibility to integrate space-time processing into the time-domain backprojection process. This combination allows detection as well as imaging moving objects. Two space-time techniques, Displaced Phase Center Antenna (DPCA) and Space-Time Adaptive Processing (STAP), are considered for this integration. Simulated results based on the LORA parameters demonstrate the efficiency of detection and imaging moving objects.

  • 99. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Moving target detection by focusing for frequency-domain algorithms in UWB low frequency SAR2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Moving target detection at low radar frequencies is associated with long integration time and has to handle azimuth focusing for reliable detection. The detection by focusing in which time-domain is the basis for the focusing approach has been proposed and successfully experimented in reality. The main objective of this paper is to apply and evaluate the detection method for frequency-domain algorithms. Range Migration Algorithm (RM) is chosen as a candidate for this study due to the accuracy of the algorithm with very wide integration angles. The simulated SAR data, which is used in this study, is based on the parameters of an airborne UWB low frequency system such as CARABAS-II.

  • 100.
    Vu, Viet Thuy
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Moving Target Focusing with Normalized Relative Speed in Azimuth-Invarian Bistatic Sar2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Focusing moving targets with Normalized Relative Speed (NRS) for bistatic synthetic aperture radar (SAR) is discussed in this paper. The discussion concentrates on azimuth invariant bistatic geometry. The focusing approach for azimuth-invariant bistatic geometry is derived analytically. The validity of the proposed approach for other bistatic geometry like azimuth-variant is also investigated.

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