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  • 101. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Håkansson, Lars
    Gustavsson, Anders
    Ulander, Lars
    RFI Suppression in Ultrawideband SAR Using an Adaptive Line Enhancer2010In: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 7, no 4, p. 694-698Article in journal (Refereed)
    Abstract [en]

    In this letter, we propose an approach to suppress radio-frequency interference (RFI) in ultrawideband (UWB) low-frequency synthetic aperture radar (SAR). According to the proposal, RFI is suppressed by using an adaptive line enhancer controlled by the normalized least mean square algorithm. The approach is tested successfully on real UWB low-frequency SAR data. In order to keep the computational burden down, possible ways to integrate the RFI suppression approach into SAR imaging algorithms are also suggested.

  • 102. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Marques, Paulo
    Application of Moving Target Detection by Focusing Technique in Civil Traffic Monitoring2010Conference paper (Refereed)
    Abstract [en]

    This paper presents an application of the detection of moving target by focusing technique (DMTF) in civil traffic monitoring. With an assumption of known moving directions of vehicles, DMTF allows first detecting these vehicles, then estimating their speed and finally imaging the vehicles of interest. With DMTF, the civil traffic monitoring requires only a singlechannel airborne SAR system.

  • 103.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Sjögren, Thomas
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Pettersson, Mats
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Minardi, Michael
    The Availability ff Fast Time-Domain Algorithms for Circular Sar Data Processing2012Conference paper (Refereed)
    Abstract [en]

    The paper shows an investigation of the availability of the fast time-domain algorithms to process data collected by synthetic aperture radar systems with circular apertures (CSAR). In the investigation, the reconstruction of CSAR images from data is suggested to be in a ground plane instead of a slant-range plane. The Fast Backprojection (FBP) algorithms are considered to examine the availability of time-domain algorithms for CSAR data processing. However, the availability is also applied to the Fast Factorized Backprojection (FFBP) algorithms. The simulated CSAR data with respect to the CARABAS-II parameters is used.

  • 104. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Zepernick, Hans-Jürgen
    Gustavsson, Anders
    Experimental Results on Moving Targets Focusing in UWB Low Frequency SAR2007Conference paper (Refereed)
    Abstract [en]

    The main objective of this paper is to present and evaluate a method to detect moving targets in Ultra Wideband (UWB) low frequency Synthetic Aperture Radar (SAR). Moving target detection at low radar frequencies is associated with long integration time and has to handle azimuth focusing for reliable detection. The examined method tests different hypotheses on relative speeds in the area of interest. The optimum step size between the hypotheses is found from a point target approximation. Experimental results show that the ability to detect moving targets increases significantly. In this study, the improvement of the Signal-to-Clutter Noise Ratio (SCNR) is up to approximately 20dB using a single antenna. The focusing method allows initial estimates in speed of moving targets. The SAR data, which is used in our experiments, was collected by the airborne UWB low frequency CARABAS-II system.

  • 105.
    Zepernick, Hans-Jürgen
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Lundberg, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Systems and Software Engineering.
    Pettersson, Mats
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Quality of Experience Based Cross-Layer Design of Mobile Video Systems2008Conference paper (Refereed)
    Abstract [en]

    This paper introduces and discusses quality of experience based cross-layer design of mobile video systems as a means of providing technologies for jointly analyzing, adopting, and optimizing system quality. The many benefits of our novel approaches over traditional concepts will range from efficient video processing techniques over advanced real-time scheduling algorithms, to networking and service level management techniques. This will lead to better service quality and resource utilization in mobile video systems.

  • 106. Zetterberg, Viktoria
    et al.
    Pettersson, Mats
    Claesson, Ingvar
    Acoustic passive 3D imaging method for scattered array2006Conference paper (Refereed)
    Abstract [en]

    An acoustic passive positioning/image method using widely distributed sensors in a network is shown. Previous studies have shown that, despite decreased coherence (due to the larger sensor separation) between sensor signals, a scattered array can give a better positioning capabillity. The positioning method divides the water into volumes and uses a weighting of each sensor pair’s correlation (Generalized Cross Correlation) result to test each volume individually. Various aspects can govern the weight assigned to a sensor pair and we have in this paper used distance from sensor to target. By projecting the correlation results over the map an intersection point is found. By looking at different depths the intersection point is found at the layer where the sound source is located. 3D positioning though requires an end fire sensor pair close to the sound source. The more pairs of that kind, the better the position in 3D will be. The developed method is tested on both simulations and real measurement data from a measurement campaign along the Swedish coastline. In order to image moving targets by scattered sensors it is also important to Doppler compensate.

  • 107. Zetterberg, Viktoria
    et al.
    Pettersson, Mats
    Claesson, Ingvar
    Comparison between whitened generalized cross correlation and adaptive filter for time delay estimation with scattered arrays for passive positioning of moving targets in Baltic Sea shallow waters2005Conference paper (Refereed)
    Abstract [en]

    Results from an acoustic measurement campaign in shallow waters (at 22 meters depth) are given. Eight hydrophones, placed at the seabed, were used simultaneously to investigate how different distances between hydrophones affect the Time Delay Estimation (TDE). In order to position targets two TDE methods were applied. The used methods were the Generalized Cross Correlation (GCC) function weighted by the Phase Transform (PHAT) and an adaptive Normalized Least Mean Square (NLMS) filter estimating the TDE between pairs of sensors. The two methods gave approximately the same result, except for the largest baseline where the GCC PHAT performed better. In the study we found that increasing separation distance decrease the bandwidth of coherence between the signals, however the study also indicated that scattered arrays with large baselines has better positioning capability than those with small baselines.

  • 108. Zetterberg, Viktoria
    et al.
    Pettersson, Mats
    Tegberg, Lars
    Claesson, Ingvar
    Passive scattered array positioning method for underwater acoustic source2006Conference paper (Refereed)
    Abstract [en]

    This paper considers large scattered arrays for 3D underwater acoustic positioning and imaging, where the hydrophone sensors, in the array, form a network over the total area of interest. A method where the Generalized Cross Correlation (GCC) function is projected over the volume is being used, and 3D images are formed. In this paper we determine the discretization of these images so they fulfill the Nyqvist criteria. In order to detect and position targets by scattered sensors it is important to Doppler compensate and weight the different sensor pair results. In this paper we divide the water into volumes where Doppler compensation and pair weights are implemented for each volume individually. Various aspects can govern the weights assigned to a sensor pair and in this paper we have used opening angle between sensor pair and target. The baseline of the sensor pairs varies from 17 – 181 meters, therefore different frequency bandwidths for each sensor pair is used. The developed method is tested on both simulations and real measurement for a surface target.

123 101 - 108 of 108
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