The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform

Renbiao Wu - One of the best experts on this subject based on the ideXlab platform.

  • migration through Resolution Cell compensation in isar imaging
    IEEE Geoscience and Remote Sensing Letters, 2004
    Co-Authors: Mengdao Xing, Renbiao Wu
    Abstract:

    Range-Doppler (RD) processing is widely used in conventional inverse synthetic aperture radar (ISAR) imaging. The unwanted translational motion of moving targets is compensated by envelope alignment and autofocus. For existing ISAR imaging algorithms, the scatterers' migration through Resolution Cells (MTRC) caused by the rotational motion is usually ignored. With the improvement of Resolution or the increase of target size, MTRC cannot be neglected. In this letter, the keystone formatting algorithm developed in SAR is used for the MTRC compensation in ISAR. Before the keystone formatting, coherent processing must be performed on the raw phase history data. An effective approach is proposed for this kind of coherent processing. Numerical examples are provided to demonstrate the performance of the proposed approach.

Blas Pablo Dorta-naranjo - One of the best experts on this subject based on the ideXlab platform.

  • SAR System for UAV Operation with Motion Error Compensation beyond the Resolution Cell
    Sensors, 2008
    Co-Authors: J.-t. González-partida, P. Almorox-gonzález, M. Burgos-garcía, Blas Pablo Dorta-naranjo
    Abstract:

    This paper presents an experimental Synthetic Aperture Radar (SAR) system that is under development in the Universidad Politecnica de Madrid. The system uses Linear Frequency Modulated Continuous Wave (LFM-CW) radar with a two antenna configuration for transmission and reception. The radar operates in the millimeter-wave band with a maximum transmitted bandwidth of 2 GHz. The proposed system is being developed for Unmanned Aerial Vehicle (UAV) operation. Motion errors in UAV operation can be critical. Therefore, this paper proposes a method for focusing SAR images with movement errors larger than the Resolution Cell. Typically, this problem is solved using two processing steps: first, coarse motion compensation based on the information provided by an Inertial Measuring Unit (IMU); and second, fine motion compensation for the residual errors within the Resolution Cell based on the received raw data. The proposed technique tries to focus the image without using data of an IMU. The method is based on a combination of the well known Phase Gradient Autofocus (PGA) for SAR imagery and typical algorithms for translational motion compensation on Inverse SAR (ISAR). This paper shows the first real experiments for obtaining high Resolution SAR images using a car as a mobile platform for our radar.

  • SAR system for UAV operation with motion error compensation beyond the Resolution Cell
    Sensors, 2008
    Co-Authors: J.-t. González-partida, P. Almorox-gonzález, M. Burgos-garcía, Blas Pablo Dorta-naranjo
    Abstract:

    This paper presents an experimental Synthetic Aperture Radar (SAR) system that is under development in the Universidad Politécnica de Madrid. The system uses Linear Frequency Modulated Continuous Wave (LFM-CW) radar with a two antenna configuration for transmission and reception. The radar operates in the millimeter-wave band with a maximum transmitted bandwidth of 2 GHz. The proposed system is being developed for Unmanned Aerial Vehicle (UAV) operation. Motion errors in UAV operation can be critical. Therefore, this paper proposes a method for focusing SAR images with movement errors larger than the Resolution Cell. Typically, this problem is solved using two processing steps: first, coarse motion compensation based on the information provided by an Inertial Measuring Unit (IMU); and second, fine motion compensation for the residual errors within the Resolution Cell based on the received raw data. The proposed technique tries to focus the image without using data of an IMU. The method is based on a combination of the well known Phase Gradient Autofocus (PGA) for SAR imagery and typical algorithms for translational motion compensation on Inverse SAR (ISAR). This paper shows the first real experiments for obtaining high Resolution SAR images using a car as a mobile platform for our radar.

Eric Pottier - One of the best experts on this subject based on the ideXlab platform.

  • First Investigations on Influence of Resolution Cell Size for Monitoring Bare Agricultural Soil by using Ground Based SAR (PoSAR) System Measurements
    2014 44th European Microwave Conference, 2014
    Co-Authors: Sophie Allain, Stephane Meric, Hongquan Wang, Eric Pottier
    Abstract:

    —The objective of this study is to evaluate the influence of Resolution Cell size of a SAR image in order to monitor bare agricultural soil. In order to achieve this objective, we propose to use Ground Based (GB) SAR experiments, in which the specific levels of surface roughness and soil moisture are set deliberately. For these first investigations, we propose to study the backscattering coefficients σHH for different surface roughness values regarding multi-Resolution. These first results we obtained with our GB-SAR system (called PoSAR for Pocket SAR) are in agreement with previous experiments on indoor SAR measurements (JRC dataset).

  • 3D urban remote sensing using dual-baseline POL-inSAR images at L-band
    International Geoscience and Remote Sensing Symposium (IGARSS), 2008
    Co-Authors: Stefan Sauer, Andreas Reigber, Laurent Ferro-famil, Eric Pottier
    Abstract:

    This paper generalizes a multibaseline interferometric SAR signal model to the polarimetric configuration. Based on this formulation, two high-performance array signal processing techniques are adapted to analyze multibaseline POL-InSAR observations. These new methods enhance the height estimation of scatterers by calculating optimal polarization combinations and allow the determination of their physical characteristics. Applying the algorithms to urban environments, the building layover problem is resolved by means of polarimetric dual-baseline InSAR measurements: Up to two components within one azimuth-range Resolution Cell are separated. The techniques are tested using dual-baseline Pol-InSAR data acquired by DLR's E-SAR system over Dresden city.

  • 3D visualisation and physical feature extraction of urban areas using multibaseline POL-InSAR Data at L-Band
    2007 Urban Remote Sensing Joint Event, URS, 2007
    Co-Authors: Stefan Sauer, Laurent Ferro-famil, Eric Pottier, Andreas Reigber
    Abstract:

    This paper extends two single polarization multibaseline interferometric SAR spectral analysis techniques to the fully polarimetric configuration. These new algorithms enhance the height estimation of scatterers by calculating optimal polarization combinations and allow to determine their physical characteristics. First experimental results show the retrieval of building height and their polarimetric properties by means of single-baseline polarimetric datasets. Dual-baseline observations permit the solution of the layover problem by separating two contributions within one Resolution Cell. The algorithms are tested using multibaseline Pol-InSAR data acquired by DLR’s E-SAR system.

  • Influence of Resolution Cell size for surface parameters retrieval from polarimetric SAR data
    IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477), 2003
    Co-Authors: Sophie Allain, Laurent Ferro-famil, Eric Pottier, Joaquim Fortuny
    Abstract:

    This paper introduces a study of the influence of the size of SAR Resolution Cell on polarimetric scattering characteristics over rough surfaces. Surface scattering is shown to be dependent on the Cell size to correlation length ratio. SAR Resolution is taken into account by dividing a surface spectrum in two parts: a low-frequency spectrum corresponding to local slopes and a high-frequency component, defining the roughness inside a Resolution Cell. Backscattering coefficients are calculated for each Resolution Cell with the IEM model using local incidence angles. Surface scattering is characterized with three polarimetric indicators H/A//spl alpha//spl I.bar/, highly related to the soil characteristics. These models are validated on indoor polarimetric SAR measurements acquired at the JRC laboratory.

Mengdao Xing - One of the best experts on this subject based on the ideXlab platform.

  • migration through Resolution Cell compensation in isar imaging
    IEEE Geoscience and Remote Sensing Letters, 2004
    Co-Authors: Mengdao Xing, Renbiao Wu
    Abstract:

    Range-Doppler (RD) processing is widely used in conventional inverse synthetic aperture radar (ISAR) imaging. The unwanted translational motion of moving targets is compensated by envelope alignment and autofocus. For existing ISAR imaging algorithms, the scatterers' migration through Resolution Cells (MTRC) caused by the rotational motion is usually ignored. With the improvement of Resolution or the increase of target size, MTRC cannot be neglected. In this letter, the keystone formatting algorithm developed in SAR is used for the MTRC compensation in ISAR. Before the keystone formatting, coherent processing must be performed on the raw phase history data. An effective approach is proposed for this kind of coherent processing. Numerical examples are provided to demonstrate the performance of the proposed approach.

Peter Willett - One of the best experts on this subject based on the ideXlab platform.

  • IR pixel size optimization from a tracking perspective
    Signal and Data Processing of Small Targets 2004, 2004
    Co-Authors: Xin Zhang, Peter Willett, Yaakov Bar-shalom
    Abstract:

    This paper considers the optimal Resolution Cell (pixel) size in detection and tracking IR targets. Using refined Resolution can help localizing the position of the targets precisely. However, along with a smaller Resolution Cell the signal power in each Resolution Cell becomes lower, because a point target is recorded as a blur according to the point spread function (PSF). Meanwhile, since the noise power is proportional to the area of the pixel, the noise is also lower. On the other hand, using coarse Resolution (which is the result of opting for a high signal power in the Resolution Cell) renders less accurate target position estimates together with higher noise power. That is, as the pixel size changes there is a trade-off in terms of detection performance versus estimation accuracy. We submit that the only defensible way to rationalize this is from system level concerns: what is best for tracking? We will first look at the initial state estimation of a constant velocity target. Relationships between the Cramer-Rao lower bound for the initial state estimation and the Resolution Cell size will be established. Then, from a general target tracking perspective, the pixel-size effects on the probability of detection and the target location centroiding accuracy will be analyzed.

  • From the waveform through the Resolution Cell to the tracker
    1999 IEEE Aerospace Conference. Proceedings (Cat. No.99TH8403), 1999
    Co-Authors: Peter Willett, Yaakov Bar-shalom
    Abstract:

    Waveform selection problems and some sidelobe-reduction techniques are investigated from a system engineering point of view via the hybrid conditional averaging (HYCA) method. A probabilistic data association filter (PDAF) is assumed in the HYCA method. The Resolution Cells are defined as tesselating parallelograms with constant volume, which are oriented and shaped to match the ambiguity function. The detection model is improved by considering the effect of detections in neighboring Cells caused by ambiguity function sidelobes. Both Swerling 1 and Swerling 3 target models are investigated. Results indicate that up-sweep linear FM (LFM), and 50%-50% upsweep LFM with low sweep rate/CF combination, are both competitive choices. As far as the two kinds of sidelobe-reduction techniques are concerned, Hamming windowing is found preferable to Gaussian shading. The effect of the detection threshold is also studied. For the constant volume of the Resolution Cell, we take that volume as natural for the CF waveform. From the coded pulse results, it appears that this volume is an important parameter to be varied in future investigations.

  • Predetection fusion: Resolution Cell grid effects
    IEEE Transactions on Aerospace and Electronic Systems, 1999
    Co-Authors: C. Rago, Peter Willett, M. Alford
    Abstract:

    If members of a suite of sensors from which fusion is to be carried out are not colocated, it is unreasonable to assume that they share a common Resolution Cell grid; this is generally ignored in the data fusion community. We explore the effects of such "noncoincidence", and we find that what at first seems to be a problem can in fact be exploited. The idea is that a target is known to be confined to an intersection of overlapping Resolution Cells, and this overlap is generally small. We examine noncoincidence from two viewpoints: tracking and detection. With respect to tracking our analysis is first static, by which is meant that we establish the decrease in measurement error; and then dynamic, meaning that the overall effect in the tracking problem is quantified. The detection viewpoint considers noncoincidence as it has impact on a predetection fusion system. Specifically, the role of the fusion rule is examined, and the use of noncoincidence to improve detection performance (rather than that of tracking) is explored.

  • Data-Fusion: Performance Enhancement Via Resolution Cell Processing.
    1995
    Co-Authors: C. Rago, Peter Willett
    Abstract:

    Abstract : This report discusses the Resolution Cell grid topological connectedness as understood by a plurality of sensors. This is a data fusion obstacle ignored by previous multisensor fusion treatments. This connectedness, if properly considered, can provide enhanced Resolution. The noncoherent case draws attention to the sort of processing necessary when multiplatform fusion is used. The problem is described and analyzed for both the static and dynamic cases. Since performance gains depend on the fusion rule used, pre-detection fusion rules are developed. 'Same-sensor' fusion makes use of the complementary features, detection, and Resolution of long and short pulses. This teaming approach appears very promising. If different single sensor pulses are fused, then coherent processing is possible. A pair of different complementary pulses is transmitted abutted in the time domain and the returns optimally fused. Combined constant frequency and linearly frequency modulated pulses are treated, and order magnitude tracking error reduction over isolated single pulse performance is demonstrated.

  • Tracking with fused noncoincident measurements
    Signal and Data Processing of Small Targets 1994, 1994
    Co-Authors: C. Rago, Peter Willett, Yaakov Bar-shalom
    Abstract:

    If members of a suite of sensors from which fusion is to be carried out are not co-located, it is unreasonable to assume that they share a common Resolution Cell grid; this is generally ignored in the data fusion community. In this paper we explore the effects of such `noncoincidence', and we find that what at first seems to be a problem can in fact be exploited. The idea is that a target is known to be confined to an intersection of overlapping Resolution Cells, and this overlap is generally small.