alessandra budillon | Università degli studi di Napoli "Parthenope" (original) (raw)

Papers by alessandra budillon

IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium

Backscattering separation coming from ground and canopy is one of the main aims in dealing with f... more Backscattering separation coming from ground and canopy is one of the main aims in dealing with forest scenario using synthetic aperture radar (SAR) tomography. Theoretically SAR tomography (TomoSAR) provides layover solution, but in practice, insufficient vertical resolution using typical reconstruction approaches may not be sufficient for identification of the vertically aligned scatterers. To cope with this intrinsic issue, we proposed a method that separates the ground and canopy backscatterings based on Random- Volume-over-Ground (RVOG) model and by employing the generalized likelihood ratio test (GLRT) detection schemes over the covariance matrix. Such a separation allows identification of interference of the backscattering, which simply brings the possibility to resolve and separate ground and canopy superposition in the tomogram. Experimental validation of the proposed methodology is provided using a real data set acquired by the ONERA SETHI in the framework of the ESA’s campaign, TropiSAR.

Infrastructures, 2022

Structural health monitoring and damage detection tools are extremely important topics nowadays w... more Structural health monitoring and damage detection tools are extremely important topics nowadays with the civil infrastructure aging and deteriorating problems observed in urban areas. These tasks can be done by visual inspection and by using traditional in situ methods, such as leveling or using traditional mechanical and electrical sensors, but these approaches are costly, labor-intensive and cannot be performed with a high temporal frequency. In recent years, remote sensing has proved to be a very promising methodology in evaluating the health of a structure by assessing its deformation and thermal dilation. The satellite-based Synthetic Aperture Radar Tomography (TomoSAR) technique, based on the exploitation of a stack of multi-temporal SAR images, allows to remotely sense the movement and the thermal dilation of individual structures with a centimeter- to millimeter-level accuracy, thanks to new generation high-resolution satellite-borne sensors. In this paper, the effectiveness...

IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium, 2020

Synthetic Aperture Radar (SAR) tomographic techniques enable the reconstruction of the scene scat... more Synthetic Aperture Radar (SAR) tomographic techniques enable the reconstruction of the scene scattering structure along the vertical direction and can provide the temporal evolution of a cloud of reliable points located in the 3D space. The use of Generalized Likelihood Ratio Test approaches have been shown to be effective in selecting reliable multiple scatterers. Recently regularized tomographic methods have been proposed for increasing the density of the recovered scatterers in urban environments. This paper discusses the differences between these two approaches and performs a comparison of reconstruction results obtained from a stack of TerraSAR-X images, in a region of interest located in the city of Paris, France.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2022

Multilook approaches have been applied in synthetic aperture radar (SAR) tomography (TomoSAR), fo... more Multilook approaches have been applied in synthetic aperture radar (SAR) tomography (TomoSAR), for improving the density and regularity of persistent scatterers reconstructed from multipass SAR images in both rural and urban regions. Multilook operations assume that all scatterers in a given neighborhood are similar in height, thereby providing additional data for recovering the position and reflectivity of a single scatterer, so that a higher signal-to-noise ratio can be achieved. This is equivalent to assuming that scatterers belonging to a local neighborhood of range-azimuth cells are located on horizontal planes. The present article generalizes this approach by adopting the so-called local plane (LP) model for TomoSAR imaging in urban areas, accounting for local variations in the height of scatterers that are not negligible. Furthermore, an LP-generalized likelihood ratio test (LP-GLRT) algorithm is developed to implement the previous idea. Compared with the multilook generalized likelihood ratio test algorithm, LP-GLRT shows better performance in the case of urban structures and terrains in experiments based on both simulated data and TerraSAR-X images. Index Terms-Generalized likelihood ratio test (GLRT), local plane (LP), multilook, synthetic aperture radar (SAR) tomography (TomoSAR). I. INTRODUCTION S YNTHETIC aperture radar (SAR) tomography (To-moSAR) is an effective tool for unmixing overlapped reflectivity contributions in the same range-azimuth cells. It fully resolves the three-dimensional (3-D) position of the detected scatterers by exploiting the information inside multipass images over the same scene [1]-[4]. This technique and its extensions to higher dimensional cases [5], [6] have been implemented for several applications, including SAR imaging of urban and forested areas [7]-[12] and deformation monitoring Manuscript

IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium, 2019

This paper deals with the characterization of permanent scatterers in polarimetric synthetic aper... more This paper deals with the characterization of permanent scatterers in polarimetric synthetic aperture radar (SAR) images of urban environment. To this aim, the main purpose of this paper is to investigate how spaceborne SAR tomography (TomoSAR) can be employed to identify and distinguish the target scattering mechanisms. Along this, the conventional H-α classifier can be adapted to the reconstructed polarimetric coherence matrix, i.e. T, in a multi-dimensional space. However, dealing with multitemporal multi-baseline satellite images, the accurate tomographic reconstruction requires permanent scatterers between all the acquisitions. To cope with this issue, a generalized likelihood ratio test (GLRT)-based tomographic approach for polarimetric SAR tomography is developed. The proposed framework of scatterer detection and characterization is evaluated using TerraSAR-X polarimetric multi-baseline data sets over an urban area in France.

Lecture Notes in Civil Engineering, 2021

In this paper the performance of two compression methods for SAR images, based on an overcomplete... more In this paper the performance of two compression methods for SAR images, based on an overcomplete Independent Component Analysis and on a Compressive Sampling approach are analyzed. The two approaches are analyzed and compared on different set of real SAR COSMO-SkyMed data. Keywords-Synthetic Aperture Radar; Compression; Independent Component Analysis; Compressive Sampling

2004 12th European Signal Processing Conference, 2004

Control of prosodic characteristics is one of the most important problems in the area of speech s... more Control of prosodic characteristics is one of the most important problems in the area of speech synthesis. Fujisaki's model is probably the best model for pitch variations and its inversion is suitable for being integrated within speech synthesizres. This paper proposes a speech synthesis method based on Fujisaki's model (combined direct and inverse modeling) in order to preserve natural soundness of synthesized speech. The idea is to modify a pitch contour on the basis of Fujisaki's features and a reference contour. Experimental results have shown that using constraints related to Fujisaki's model guarantees good natural-sounding speech synthesis.

2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS, 2021

In this paper a Polarimetric SAR Tomographic (Pol-TomoSAR) technique, exploiting the local contex... more In this paper a Polarimetric SAR Tomographic (Pol-TomoSAR) technique, exploiting the local contextual information in small neighborhoods surrounding each range-azimuth pixel, is applied to fully polarimetric multi-baseline images of an urban area. In particular, the considered technique is based on the assumption that the pixels belonging to a neighborhood are located on a locally planar surface, whose slopes can be estimated for each range-azimuth pixel from the surrounding neighboring data. This assumption well adapts to urban areas, where the height profile can be well approximated by planes. In this way, the correlation among the heights of neighboring pixels can be taken into account for improving the accuracy of the height profile reconstruction. Preliminary results on fully polarization SAR data are presented.

IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018

Synthetic aperture radar (SAR) tomography is the most typical approach to generate the elevation ... more Synthetic aperture radar (SAR) tomography is the most typical approach to generate the elevation map of the observed scene through the 3D imaging from multi-baseline acquisition. Typically, the nominal scatterers can be derived by evaluation of the presented peaks in the reconstructed scattering reflectivity through the array signal processing methods. In this paper, we investigate the possibility to improve the height reconstruction process and achieve a reliable elevation map by jointly estimating and regularizing the solution of array processing techniques. In particular, an a priori is added to the cost function of desired parameter estimation in the processing chain. The algorithm is evaluated using simulated data correspond to the E-SAR airborne sensor of the German Aerospace Center (DLR).

IEEE Geoscience and Remote Sensing Magazine, 2020

In this paper, we present a concept for a compact ultra-wideband multielement antenna (MEA) for m... more In this paper, we present a concept for a compact ultra-wideband multielement antenna (MEA) for massive MIMO indoor base stations. The antenna concept is based on the simultaneous excitation of different characteristic modes on each element of the MEA. This enables an effective 484 port antenna using only 121 physical antenna elements. Thereby, a size reduction of 54% compared to a generic MEA based on crossed dipoles is achieved. The antenna operates in the ultra-wide frequency band of 6-8.5 GHz with a reflection coefficient of sii < −10 dB and the interelement and intraelement mutual coupling of the antenna ports is sji ≤ −20 dB.

Remote Sensing, 2019

This Special Issue hosts papers related to deformation monitoring in urban areas based on two mai... more This Special Issue hosts papers related to deformation monitoring in urban areas based on two main techniques: Persistent Scatterer Interferometry (PSI) and Synthetic Aperture Radar (SAR) Tomography (TomoSAR). Several contributions highlight the capabilities of Interferometric SAR (InSAR) and PSI techniques for urban deformation monitoring. In this Special Issue, a wide range of InSAR and PSI applications are addressed. Some contributions show the advantages of TomoSAR in un-mixing multiple scatterers for urban mapping and monitoring. This issue includes a contribution that compares PSI and TomoSAR and another one that uses polarimetric data for TomoSAR.

Remote Sensing, 2019

In this paper, we investigate the potential of polarimetric Synthetic Aperture Radar (SAR) tomogr... more In this paper, we investigate the potential of polarimetric Synthetic Aperture Radar (SAR) tomography (Pol-TomoSAR) in urban applications. TomoSAR exploits the amplitude and phase of the received data and offers the possibility to resolve multiple scatters lying in the same range–azimuth resolution cell. In urban environments, this issue is very important since layover causes multiple coherent scatterers to be mapped in the same range–azimuth image pixel. To achieve reliable and accurate results, TomoSAR requires a large number of multi-baseline acquisitions which, for satellite-borne SAR systems, are collected with long time intervals. Then, accurate tomographic reconstructions would require multiple scatterers to remain stable between all the acquisitions. In this paper, an extension of a generalized likelihood ratio test (GLRT)-based tomographic approach, denoted as Fast-Sup-GLRT, to the polarimetric data case is introduced, with the purpose of investigating if, in urban applicat...

Remote Sensing, 2018

In this paper, persistent scatterer interferometry and Synthetic Aperture Radar (SAR) tomography ... more In this paper, persistent scatterer interferometry and Synthetic Aperture Radar (SAR) tomography have been applied to Sentinel-1 data for urban monitoring. The paper analyses the applicability of SAR tomography to Sentinel-1 data, which is not granted, due to the reduced range and azimuth resolutions and the low resolution in elevation. In a first part of the paper, two implementations of the two techniques are described. In the experimental part, the two techniques are used in parallel to process the same Sentinel-1 data over two test areas. An intercomparison of the results from persistent scatterer interferometry and SAR tomography is carried out, comparing the main parameters estimated by the two techniques. Finally, the paper addresses the complementarity of the two techniques, and in particular it assesses the increase of measurement density that can be achieved by adding the double scatterers from SAR tomography to the persistent scatterer interferometry measurements.

Remote Sensing, 2017

This paper analyzes a method for Synthetic Aperture Radar (SAR) Tomographic (TomoSAR) imaging, al... more This paper analyzes a method for Synthetic Aperture Radar (SAR) Tomographic (TomoSAR) imaging, allowing the detection of multiple scatterers that can exhibit time deformation and thermal dilation by using a CFAR (Constant False Alarm Rate) approach. In the last decade, several methods for TomoSAR have been proposed. The objective of this paper is to present the results obtained on high resolution tomographic SAR data of urban areas, by using a statistical test for detecting multiple scatterers that takes into account phase variations due to possible deformations and/or thermal dilation. The test can be evaluated in terms of probability of detection (P D) and probability of false alarm (P FA), and is based on an approximation of a Generalized Likelihood Ratio Test (GLRT), denoted as Fast-Sup-GLRT. It was already applied and validated by the authors in the 3D case, while here it is extended and experimented in the 5D case. Numerical experiments on simulated and on StripMap TerraSAR-X (TSX) data have been carried out. The presented results show that the adopted method allows the detection of a large number of scatterers and the estimation of their position with a good accuracy, and that the consideration of the thermal dilation and surface deformation helps in recovering more single and double scatterers, with respect to the case in which these contributions are not taken into account. Moreover, the capability of method to provide reliable estimates of the deformations in urban structure suggests its use in structure stress monitoring.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2017

This paper is focused on the problem of the detection of multiple scatterers in synthetic apertur... more This paper is focused on the problem of the detection of multiple scatterers in synthetic aperture radar (SAR) tomography. The method presented exploits the a priori information that at most K m ax different scatterers are present in the same range-azimuth resolution cell. In particular, a simplified version of a generalized-likelihood ratio test (GLRT) detector, based on support estimation (Sup-GLRT), is proposed. The Sup-GLRT is a constant false alarm rate sequential test that detects the presence of scatterers, one after another, and estimates their positions, detecting the support of the unknown signal. The proposed simplified test denoted as Fast-Sup-GLRT detector, despite still being a multistep statistical hypothesis test, exploits, at each step i, an approximated maximum-likelihood estimate of the signal support of cardinality i−1, based on the sequential estimation of i−1 supports of cardinality one. The introduced approximation allows a considerable reduction of the computational complexity, which from the combinatorial trend of Sup-GLRT passes to the linear one of Fast-Sup-GLRT, without significantly impairing the detection probability. The performance of the proposed approach is analyzed using TerraSAR-X system parameters, with particular reference to the elevation superresolution achievable for an assigned probability of false alarm and with a given number of acquisitions. Numerical results on simulated and real data are presented and discussed.

The Scientific World Journal, 2015

The problem of detecting and locating multiple scatterers in multibaseline Synthetic Aperture Rad... more The problem of detecting and locating multiple scatterers in multibaseline Synthetic Aperture Radar (SAR) tomography, starting from compressive measurements and applying support detection techniques, is addressed. Different approaches based on the detection of the support set of the unknown sparse vector, that is, of the position of the nonzero elements in the unknown sparse vector, are analyzed. Support detection techniques have already proved to allow a reduction in the number of measurements required for obtaining a reliable solution. In this paper, a support detection method, based on a Generalized Likelihood Ratio Test (Sup-GLRT), is proposed and compared with the SequOMP method, in terms of probability of detection achievable with a given probability of false alarm and for different numbers of measurements.

IEEE Transactions on Geoscience and Remote Sensing, 2015

The availability of high-resolution along-track interferometric synthetic aperture radar (ATI-SAR... more The availability of high-resolution along-track interferometric synthetic aperture radar (ATI-SAR) data with large coverage, such as TerraSAR-X (TSX) data, motivates spaceborne ground moving target detection as an attractive alternative to conventional traffic data acquisition. In this paper, a performance analysis of ground moving targets detection by means of ATI-SAR systems and using a statistical approach is carried out on both simulated and real data. A Gaussian clutter model and a deterministic target response have been assumed. The receiver operating characteristic for the likelihood ratio test (LRT), which can be assumed as a reference best performance case, has been expressed in closed form and has been related to the deflection values, which can be exploited for assessing the improvements in the detection probability with a constant false-alarm rate. For practical applications, the performance of a generalized LRT (GLRT) has been investigated. The analysis carried out on simulated data revealed that the detection results achieved using a GLRT based on a deterministic target model are comparable with those obtained using a GLRT based on a Gaussian target model and are not significantly worse than the theoretical performance of the LRT. Finally, ground moving target detection results on TSX real data are showed.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2014

ABSTRACT Multibaseline interferometric synthetic aperture radar (In-SAR) systems are used to obta... more ABSTRACT Multibaseline interferometric synthetic aperture radar (In-SAR) systems are used to obtain the height profile of the observed ground scene with high accuracy. The techniques that are commonly used exploit only the interferometric phase information, and are based on maximum likelihood (ML) estimation. Due to the difficulty of expressing the multibaseline likelihood function in closed form, they adopt the statistical independence approximation of the interferometric phases. In this paper, we investigate the effect of this approximation, and analyze the performance of two statistical methods exploiting complex SAR images, which takes into account the mutual correlation among all the interferometric images. These two methods are based on a local and a contextual approach. The local one is based on an ML estimator, and processes each pixel independently from the neighboring ones. The contextual approach adopts a Bayesian estimator in order to regularize and improve the height reconstruction. The presented results show that the inclusion of SAR image correlation information allows to improve the height reconstruction accuracy. The proposed method also provides an estimation of speckle-reduced image intensity.

IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium

Backscattering separation coming from ground and canopy is one of the main aims in dealing with f... more Backscattering separation coming from ground and canopy is one of the main aims in dealing with forest scenario using synthetic aperture radar (SAR) tomography. Theoretically SAR tomography (TomoSAR) provides layover solution, but in practice, insufficient vertical resolution using typical reconstruction approaches may not be sufficient for identification of the vertically aligned scatterers. To cope with this intrinsic issue, we proposed a method that separates the ground and canopy backscatterings based on Random- Volume-over-Ground (RVOG) model and by employing the generalized likelihood ratio test (GLRT) detection schemes over the covariance matrix. Such a separation allows identification of interference of the backscattering, which simply brings the possibility to resolve and separate ground and canopy superposition in the tomogram. Experimental validation of the proposed methodology is provided using a real data set acquired by the ONERA SETHI in the framework of the ESA’s campaign, TropiSAR.

Infrastructures, 2022

Structural health monitoring and damage detection tools are extremely important topics nowadays w... more Structural health monitoring and damage detection tools are extremely important topics nowadays with the civil infrastructure aging and deteriorating problems observed in urban areas. These tasks can be done by visual inspection and by using traditional in situ methods, such as leveling or using traditional mechanical and electrical sensors, but these approaches are costly, labor-intensive and cannot be performed with a high temporal frequency. In recent years, remote sensing has proved to be a very promising methodology in evaluating the health of a structure by assessing its deformation and thermal dilation. The satellite-based Synthetic Aperture Radar Tomography (TomoSAR) technique, based on the exploitation of a stack of multi-temporal SAR images, allows to remotely sense the movement and the thermal dilation of individual structures with a centimeter- to millimeter-level accuracy, thanks to new generation high-resolution satellite-borne sensors. In this paper, the effectiveness...

IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium, 2020

Synthetic Aperture Radar (SAR) tomographic techniques enable the reconstruction of the scene scat... more Synthetic Aperture Radar (SAR) tomographic techniques enable the reconstruction of the scene scattering structure along the vertical direction and can provide the temporal evolution of a cloud of reliable points located in the 3D space. The use of Generalized Likelihood Ratio Test approaches have been shown to be effective in selecting reliable multiple scatterers. Recently regularized tomographic methods have been proposed for increasing the density of the recovered scatterers in urban environments. This paper discusses the differences between these two approaches and performs a comparison of reconstruction results obtained from a stack of TerraSAR-X images, in a region of interest located in the city of Paris, France.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2022

Multilook approaches have been applied in synthetic aperture radar (SAR) tomography (TomoSAR), fo... more Multilook approaches have been applied in synthetic aperture radar (SAR) tomography (TomoSAR), for improving the density and regularity of persistent scatterers reconstructed from multipass SAR images in both rural and urban regions. Multilook operations assume that all scatterers in a given neighborhood are similar in height, thereby providing additional data for recovering the position and reflectivity of a single scatterer, so that a higher signal-to-noise ratio can be achieved. This is equivalent to assuming that scatterers belonging to a local neighborhood of range-azimuth cells are located on horizontal planes. The present article generalizes this approach by adopting the so-called local plane (LP) model for TomoSAR imaging in urban areas, accounting for local variations in the height of scatterers that are not negligible. Furthermore, an LP-generalized likelihood ratio test (LP-GLRT) algorithm is developed to implement the previous idea. Compared with the multilook generalized likelihood ratio test algorithm, LP-GLRT shows better performance in the case of urban structures and terrains in experiments based on both simulated data and TerraSAR-X images. Index Terms-Generalized likelihood ratio test (GLRT), local plane (LP), multilook, synthetic aperture radar (SAR) tomography (TomoSAR). I. INTRODUCTION S YNTHETIC aperture radar (SAR) tomography (To-moSAR) is an effective tool for unmixing overlapped reflectivity contributions in the same range-azimuth cells. It fully resolves the three-dimensional (3-D) position of the detected scatterers by exploiting the information inside multipass images over the same scene [1]-[4]. This technique and its extensions to higher dimensional cases [5], [6] have been implemented for several applications, including SAR imaging of urban and forested areas [7]-[12] and deformation monitoring Manuscript

IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium, 2019

This paper deals with the characterization of permanent scatterers in polarimetric synthetic aper... more This paper deals with the characterization of permanent scatterers in polarimetric synthetic aperture radar (SAR) images of urban environment. To this aim, the main purpose of this paper is to investigate how spaceborne SAR tomography (TomoSAR) can be employed to identify and distinguish the target scattering mechanisms. Along this, the conventional H-α classifier can be adapted to the reconstructed polarimetric coherence matrix, i.e. T, in a multi-dimensional space. However, dealing with multitemporal multi-baseline satellite images, the accurate tomographic reconstruction requires permanent scatterers between all the acquisitions. To cope with this issue, a generalized likelihood ratio test (GLRT)-based tomographic approach for polarimetric SAR tomography is developed. The proposed framework of scatterer detection and characterization is evaluated using TerraSAR-X polarimetric multi-baseline data sets over an urban area in France.

Lecture Notes in Civil Engineering, 2021

In this paper the performance of two compression methods for SAR images, based on an overcomplete... more In this paper the performance of two compression methods for SAR images, based on an overcomplete Independent Component Analysis and on a Compressive Sampling approach are analyzed. The two approaches are analyzed and compared on different set of real SAR COSMO-SkyMed data. Keywords-Synthetic Aperture Radar; Compression; Independent Component Analysis; Compressive Sampling

2004 12th European Signal Processing Conference, 2004

Control of prosodic characteristics is one of the most important problems in the area of speech s... more Control of prosodic characteristics is one of the most important problems in the area of speech synthesis. Fujisaki's model is probably the best model for pitch variations and its inversion is suitable for being integrated within speech synthesizres. This paper proposes a speech synthesis method based on Fujisaki's model (combined direct and inverse modeling) in order to preserve natural soundness of synthesized speech. The idea is to modify a pitch contour on the basis of Fujisaki's features and a reference contour. Experimental results have shown that using constraints related to Fujisaki's model guarantees good natural-sounding speech synthesis.

2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS, 2021

In this paper a Polarimetric SAR Tomographic (Pol-TomoSAR) technique, exploiting the local contex... more In this paper a Polarimetric SAR Tomographic (Pol-TomoSAR) technique, exploiting the local contextual information in small neighborhoods surrounding each range-azimuth pixel, is applied to fully polarimetric multi-baseline images of an urban area. In particular, the considered technique is based on the assumption that the pixels belonging to a neighborhood are located on a locally planar surface, whose slopes can be estimated for each range-azimuth pixel from the surrounding neighboring data. This assumption well adapts to urban areas, where the height profile can be well approximated by planes. In this way, the correlation among the heights of neighboring pixels can be taken into account for improving the accuracy of the height profile reconstruction. Preliminary results on fully polarization SAR data are presented.

IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018

Synthetic aperture radar (SAR) tomography is the most typical approach to generate the elevation ... more Synthetic aperture radar (SAR) tomography is the most typical approach to generate the elevation map of the observed scene through the 3D imaging from multi-baseline acquisition. Typically, the nominal scatterers can be derived by evaluation of the presented peaks in the reconstructed scattering reflectivity through the array signal processing methods. In this paper, we investigate the possibility to improve the height reconstruction process and achieve a reliable elevation map by jointly estimating and regularizing the solution of array processing techniques. In particular, an a priori is added to the cost function of desired parameter estimation in the processing chain. The algorithm is evaluated using simulated data correspond to the E-SAR airborne sensor of the German Aerospace Center (DLR).

IEEE Geoscience and Remote Sensing Magazine, 2020

In this paper, we present a concept for a compact ultra-wideband multielement antenna (MEA) for m... more In this paper, we present a concept for a compact ultra-wideband multielement antenna (MEA) for massive MIMO indoor base stations. The antenna concept is based on the simultaneous excitation of different characteristic modes on each element of the MEA. This enables an effective 484 port antenna using only 121 physical antenna elements. Thereby, a size reduction of 54% compared to a generic MEA based on crossed dipoles is achieved. The antenna operates in the ultra-wide frequency band of 6-8.5 GHz with a reflection coefficient of sii < −10 dB and the interelement and intraelement mutual coupling of the antenna ports is sji ≤ −20 dB.

Remote Sensing, 2019

This Special Issue hosts papers related to deformation monitoring in urban areas based on two mai... more This Special Issue hosts papers related to deformation monitoring in urban areas based on two main techniques: Persistent Scatterer Interferometry (PSI) and Synthetic Aperture Radar (SAR) Tomography (TomoSAR). Several contributions highlight the capabilities of Interferometric SAR (InSAR) and PSI techniques for urban deformation monitoring. In this Special Issue, a wide range of InSAR and PSI applications are addressed. Some contributions show the advantages of TomoSAR in un-mixing multiple scatterers for urban mapping and monitoring. This issue includes a contribution that compares PSI and TomoSAR and another one that uses polarimetric data for TomoSAR.

Remote Sensing, 2019

In this paper, we investigate the potential of polarimetric Synthetic Aperture Radar (SAR) tomogr... more In this paper, we investigate the potential of polarimetric Synthetic Aperture Radar (SAR) tomography (Pol-TomoSAR) in urban applications. TomoSAR exploits the amplitude and phase of the received data and offers the possibility to resolve multiple scatters lying in the same range–azimuth resolution cell. In urban environments, this issue is very important since layover causes multiple coherent scatterers to be mapped in the same range–azimuth image pixel. To achieve reliable and accurate results, TomoSAR requires a large number of multi-baseline acquisitions which, for satellite-borne SAR systems, are collected with long time intervals. Then, accurate tomographic reconstructions would require multiple scatterers to remain stable between all the acquisitions. In this paper, an extension of a generalized likelihood ratio test (GLRT)-based tomographic approach, denoted as Fast-Sup-GLRT, to the polarimetric data case is introduced, with the purpose of investigating if, in urban applicat...

Remote Sensing, 2018

In this paper, persistent scatterer interferometry and Synthetic Aperture Radar (SAR) tomography ... more In this paper, persistent scatterer interferometry and Synthetic Aperture Radar (SAR) tomography have been applied to Sentinel-1 data for urban monitoring. The paper analyses the applicability of SAR tomography to Sentinel-1 data, which is not granted, due to the reduced range and azimuth resolutions and the low resolution in elevation. In a first part of the paper, two implementations of the two techniques are described. In the experimental part, the two techniques are used in parallel to process the same Sentinel-1 data over two test areas. An intercomparison of the results from persistent scatterer interferometry and SAR tomography is carried out, comparing the main parameters estimated by the two techniques. Finally, the paper addresses the complementarity of the two techniques, and in particular it assesses the increase of measurement density that can be achieved by adding the double scatterers from SAR tomography to the persistent scatterer interferometry measurements.

Remote Sensing, 2017

This paper analyzes a method for Synthetic Aperture Radar (SAR) Tomographic (TomoSAR) imaging, al... more This paper analyzes a method for Synthetic Aperture Radar (SAR) Tomographic (TomoSAR) imaging, allowing the detection of multiple scatterers that can exhibit time deformation and thermal dilation by using a CFAR (Constant False Alarm Rate) approach. In the last decade, several methods for TomoSAR have been proposed. The objective of this paper is to present the results obtained on high resolution tomographic SAR data of urban areas, by using a statistical test for detecting multiple scatterers that takes into account phase variations due to possible deformations and/or thermal dilation. The test can be evaluated in terms of probability of detection (P D) and probability of false alarm (P FA), and is based on an approximation of a Generalized Likelihood Ratio Test (GLRT), denoted as Fast-Sup-GLRT. It was already applied and validated by the authors in the 3D case, while here it is extended and experimented in the 5D case. Numerical experiments on simulated and on StripMap TerraSAR-X (TSX) data have been carried out. The presented results show that the adopted method allows the detection of a large number of scatterers and the estimation of their position with a good accuracy, and that the consideration of the thermal dilation and surface deformation helps in recovering more single and double scatterers, with respect to the case in which these contributions are not taken into account. Moreover, the capability of method to provide reliable estimates of the deformations in urban structure suggests its use in structure stress monitoring.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2017

This paper is focused on the problem of the detection of multiple scatterers in synthetic apertur... more This paper is focused on the problem of the detection of multiple scatterers in synthetic aperture radar (SAR) tomography. The method presented exploits the a priori information that at most K m ax different scatterers are present in the same range-azimuth resolution cell. In particular, a simplified version of a generalized-likelihood ratio test (GLRT) detector, based on support estimation (Sup-GLRT), is proposed. The Sup-GLRT is a constant false alarm rate sequential test that detects the presence of scatterers, one after another, and estimates their positions, detecting the support of the unknown signal. The proposed simplified test denoted as Fast-Sup-GLRT detector, despite still being a multistep statistical hypothesis test, exploits, at each step i, an approximated maximum-likelihood estimate of the signal support of cardinality i−1, based on the sequential estimation of i−1 supports of cardinality one. The introduced approximation allows a considerable reduction of the computational complexity, which from the combinatorial trend of Sup-GLRT passes to the linear one of Fast-Sup-GLRT, without significantly impairing the detection probability. The performance of the proposed approach is analyzed using TerraSAR-X system parameters, with particular reference to the elevation superresolution achievable for an assigned probability of false alarm and with a given number of acquisitions. Numerical results on simulated and real data are presented and discussed.

The Scientific World Journal, 2015

The problem of detecting and locating multiple scatterers in multibaseline Synthetic Aperture Rad... more The problem of detecting and locating multiple scatterers in multibaseline Synthetic Aperture Radar (SAR) tomography, starting from compressive measurements and applying support detection techniques, is addressed. Different approaches based on the detection of the support set of the unknown sparse vector, that is, of the position of the nonzero elements in the unknown sparse vector, are analyzed. Support detection techniques have already proved to allow a reduction in the number of measurements required for obtaining a reliable solution. In this paper, a support detection method, based on a Generalized Likelihood Ratio Test (Sup-GLRT), is proposed and compared with the SequOMP method, in terms of probability of detection achievable with a given probability of false alarm and for different numbers of measurements.

IEEE Transactions on Geoscience and Remote Sensing, 2015

The availability of high-resolution along-track interferometric synthetic aperture radar (ATI-SAR... more The availability of high-resolution along-track interferometric synthetic aperture radar (ATI-SAR) data with large coverage, such as TerraSAR-X (TSX) data, motivates spaceborne ground moving target detection as an attractive alternative to conventional traffic data acquisition. In this paper, a performance analysis of ground moving targets detection by means of ATI-SAR systems and using a statistical approach is carried out on both simulated and real data. A Gaussian clutter model and a deterministic target response have been assumed. The receiver operating characteristic for the likelihood ratio test (LRT), which can be assumed as a reference best performance case, has been expressed in closed form and has been related to the deflection values, which can be exploited for assessing the improvements in the detection probability with a constant false-alarm rate. For practical applications, the performance of a generalized LRT (GLRT) has been investigated. The analysis carried out on simulated data revealed that the detection results achieved using a GLRT based on a deterministic target model are comparable with those obtained using a GLRT based on a Gaussian target model and are not significantly worse than the theoretical performance of the LRT. Finally, ground moving target detection results on TSX real data are showed.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2014

ABSTRACT Multibaseline interferometric synthetic aperture radar (In-SAR) systems are used to obta... more ABSTRACT Multibaseline interferometric synthetic aperture radar (In-SAR) systems are used to obtain the height profile of the observed ground scene with high accuracy. The techniques that are commonly used exploit only the interferometric phase information, and are based on maximum likelihood (ML) estimation. Due to the difficulty of expressing the multibaseline likelihood function in closed form, they adopt the statistical independence approximation of the interferometric phases. In this paper, we investigate the effect of this approximation, and analyze the performance of two statistical methods exploiting complex SAR images, which takes into account the mutual correlation among all the interferometric images. These two methods are based on a local and a contextual approach. The local one is based on an ML estimator, and processes each pixel independently from the neighboring ones. The contextual approach adopts a Bayesian estimator in order to regularize and improve the height reconstruction. The presented results show that the inclusion of SAR image correlation information allows to improve the height reconstruction accuracy. The proposed method also provides an estimation of speckle-reduced image intensity.