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In this article, we will show how to improve the standard procedure in the Annex G of IEC 61000-4-21 on the shielding effectiveness (SE) of materials and gaskets through measurements performed in reverberation chambers. We thoroughly analyze and discuss measurement models (MMs), which are already present in the literature including the standardized model. Moreover, we further derive one of these MMs in a different way and introduce a different application, which is suitable to measure high SE values. We apply such MMs and compare results. By the analysis, discussion, and comparisons of measurement results, we clearly provide a robust improvement to the standard measurement procedure.

The ability to enhance the spatial resolution of measurements collected by a conical-scanning microwave radiometer (MWR) is discussed in terms of noise amplification and improvement of the spatial resolution. Simulated (and actual) brightness temperature profiles are analyzed at variance of different intrinsic spatial resolutions and adjacent beams overlapping modeling a simplified 1-D measurement configuration (MC). The actual measurements refer to Special Sensor Microwave Imager (SSM/I) data collected using the 19.35 and the 37.00 GHz channels that match the simulated configurations. The reconstruction of the brightness profile at enhanced spatial resolution is performed using an iterative gradient method which allows a fine tuning of the level of regularization. Objective metrics are introduced to quantify the enhancement of the spatial resolution and noise amplification. Numerical experiments, performed using the simplified 1-D MC, show that the regularized deconvolution results in negligible advantages when dealing with low-overlapping/fine-spatial-resolution configurations. Regularization is a mandatory step when addressing the high-overlapping/low-spatial-resolution case and the spatial resolution can be enhanced up to 2.34 with a noise amplification equal to 1.56. A more stringent requirement on the noise amplification (up to 0.6) results in an improvement of the spatial resolution up to 1.64.

In this study, a reverberation chamber is used to perform measurements of shielding effectiveness (SE) and average total radiated power (ATRP) related to a domestic microwave oven for human exposure purposes. The ATRP is measured according to Annex E in the standard IEC 61000-4-21 procedure, and a new nondestructive procedure is proposed to measure SE that relies on the internal source of the microwave oven and on the reverberation chamber. Under mild hypothesis, the nondestructive procedure is both theoretically and experimentally equivalent to the IEEE 299.1 one. In addition, the measured ATRP values are within the limits defined in EN 62233.

In this article, a new reverberation chamber (RC) loading configuration is proposed that consists of using the conventional central barrier, i.e., absorbing material arranged on the floor of the RC, together with anechoic corners. The latter are built covering the two edges of the chamber and the nearby floor with absorbing material. This configuration, termed Semi-RC, is tested against both emulated and actual indoor wireless propagation channels. The former ones are obtained using the RC of the Universita degli Studi di Napoli “Parthenope.” The key metrics adopted to discuss the performance of the proposed approach are based on second-order channel descriptors, i.e., the power delay profile (PDP) and the autocorrelation function. Experimental results confirm the soundness of the proposed approach that outperforms the state-of-the-art central barrier loading configuration when dealing with channels calling for very steep-descendant PDPs. The two configurations result in comparable performance when slowly descendant PDPs are considered.

Sea waves constitute a natural phenomenon with a great impact on human activities, and their monitoring is essential for meteorology, coastal safety, navigation, and renewable energy from the sea. Therefore, the main measurement techniques for their monitoring are here reviewed, including buoys, satellite observation, coastal radars, shipboard observation, and microseism analysis. For each technique, the measurement principle is briefly recalled, the degree of development is outlined, and trends are prospected. The complementarity of such techniques is also highlighted, and the need for further integration in local and global networks is stressed.

The detection of wind turbines in a strong clutter background is analyzed at variance of polarimetric synthetic-aperture radar (SAR) configurations. The area of interest is the intertidal zone near Jiangsu, China and two detectors are used, the polarimetric notch filter (PNF) and a change detector that optimizes the ratio between covariance matrices. The detection performance is quantitatively analyzed using the receiver operating characteristic (ROC) curve, while the scattering mechanisms that characterize wind turbines are analyzed using the Yamaguchi decomposition. Experimental analysis shows that: 1) wind turbines result in a nontrivial scattering mechanism and 2) full-polarimetric measurements achieve the best detection performance independently of the two detectors.

In this paper, we introduce a novel approach to enhance the spatial resolution of single-pass microwave data collected by mesoscale sensors. The proposed rationale is based on an $L^{p}$ -minimization approach with a variable $p$ exponent. The algorithm automatically adapts the $p$ exponent to the region of the image to be reconstructed. This approach allows taking benefit of the advantages of both the regularization in Hilbert ( $p = 2$ ) and Banach ( $1 ) spaces. Experiments are undertaken considering the microwave radiometer and refer to both actual and simulated data collected by the special sensor microwave imager (SSM/I). Results demonstrate the benefits of the proposed method in reconstructing abrupt discontinuities and smooth gradients with respect to conventional approaches in Hilbert or Banach spaces.

A novel physical paradigm is explored in this paper: synthetic-aperture radar (SAR) ocean speckle is informative. This paper experimentally analyzes the SAR ocean speckle intensity K-distribution model versus sea-surface wind field. It is shown that the normalized intensity moments of the K-distribution measured from actual C-band SAR data well fit the theoretical ones under different wind conditions, i.e., wind regime and relative SAR-wind azimuth direction. In addition, it is observed that the K-distribution shape parameter decreases as wind speed increases. A sensitivity of the K-distribution shape parameter on incidence angle and wind direction is also observed, where the largest variability is experienced at higher incidence angles and under crosswind relative azimuth angle.

An enhanced spatial resolution brightness temperature product is proposed for future conical scan microwave radiometers. The technique is developed for Copernicus Imaging Microwave Radiometer (CIMR) measurements that are simulated using the CIMR antenna pattern at the L-band and the measurement geometry proposed in the Phase A study led by Airbus. An inverse antenna pattern reconstruction method is proposed. Reconstructions are obtained using two CIMR configurations, namely, using measurements collected at L-band by the forward (FWD) scans only, and combining forward and backward (FWD+BWD) scans. Two spatial grids are adopted, namely, 3km × 3 km and 36km × 36km. Simulation results, referred to synthetic and realistic reference brightness fields, demonstrate the soundness of the proposed scheme that provides brightness temperature fields reconstructed at a spatial resolution up to ~1.9 times finer than the measured field when using the FWD+BWD combination., This work has been produced for the European Space Agency (ESA) in the frame of the Copernicus programme as a partnership between ESA and the European Commission.

In this study, a method to improve the reconstruction performance of antenna-pattern deconvolution based on the gradient iterative regularization scheme is proposed. The method exploits microwave measurements acquired by a multichannel radiometer to enhance their native spatial resolution. The proposed rationale consists of using the information carried on a high-frequency (finer spatial resolution) channel to ameliorate the spatial resolution of the lowest resolution radiometer channel. Experiments performed using both synthetic and real special sensor microwave/imager (SSM/I) radiometer data demonstrate that an enhanced spatial resolution 19.35-GHz channel can be obtained by ingesting in the algorithm information coming from 37.0-GHz channel. This multichannel spatial resolution method is also shown to outperform the conventional gradient-like regularization scheme in terms of both observation of smaller targets and reduction of ringings and fluctuations.

In this letter, a new approach is proposed to ameliorate the performance of iterative gradient-like regularization schemes aimed at enhancing the spatial resolution of microwave radiometer measurements in the Hilbert space. The approach consists of preconditioning the ill-conditioned discrete problem to let the iterative gradient-based inversion technique be more computer-time effective. Experiments undertaken on the simulated radiometer brightness profiles demonstrate the soundness of the proposed rationale that outperforms conventional gradient-like methods in terms of both computer-time effectiveness and accuracy in reconstructing spot-like discontinuities while resulting in larger fluctuations over the background.

In this paper, we highlight the importance of high-resolution wind data on the application of multicriteria evaluation technique to colocate offshore wind farms and open-water mussel cultivations. An index of colocation sustainability (SI), based on an environmental information, is constructed using remote sensing data and taking into account both physical constraints (i.e., water depth and wind speed) and environmental data (i.e., chlorophyll-a, sea surface temperature anomaly, and particulate organic carbon). To verify the proposed methodology, five showcases are presented, where SI is evaluated considering potential installation sites in Kattegat, Denmark, using both low-resolution (LR) wind reanalysis maps related to the Modern Era Retrospective-Analysis for Research and Application data set and fine-resolution wind maps obtained by processing synthetic aperture radar (SAR) data. Experimental results show that the availability of a reliable fine-resolution wind information is of great importance in coastal areas where the presence of the land and the isles limits the use of LR wind data.

In this letter, Global Navigation Satellite System Reflectometry (GNSS-R) delay Doppler maps (DDMs) acquired by the U.K. TechDemoSat-1 (TDS-1) mission are analyzed to identify sea ice infesting waters in circumpolar areas. First, the sensitivity of actual DDM to sea ice is investigated using reference information provided by a Sentinel-1 synthetic aperture radar imagery and a Special Sensor Microwave/Imager based sea–ice concentration map. Then, a new product is proposed that consists of normalized radar cross section measurements derived from actual DDMs and arranged in gridded format. This product is shown to provide spatial information on the sea ice transition that cannot be obtained exploiting the conventional DDM product. Hence, this new product can be used to improve/complement conventional remote sensing techniques for sea ice observation.

In this paper, a time series of 33 TerraSAR-X copolarized synthetic aperture radar (SAR) imagery collected in Stripmap mode over the Gulf of Mexico in a wide range of incidence angles and sea-state condition is exploited, together with a theoretical framework based on the X-Bragg scattering model, to analyze the effects of noise, angle of incidence, (AOI) and wind speed on the standard deviation of the copolarized phase difference ( $\sigma _{\phi _{c}}$ ) evaluated over sea surface with and without oil slicks. This large data set represents an unprecedented opportunity to analyze, for the first time, the influence of both SAR acquisition and surface parameters on the broadening of the copolarized phase difference probability density function (pdf), $p_{\phi _{c}}(\phi _{c})$ . Experimental results show that the X-Bragg scattering model, here adopted to predict the sea surface $p_{\phi _{c}}(\phi _{c})$ , gives an understanding of the increasing trend of $\sigma _{\phi _{c}}$ with respect to AOI. It is shown that the noise significantly contributes to broaden $p_{\phi _{c}}(\phi _{c})$ over both slick-free and slick-covered sea surface, while the effects of low-to-moderate wind regimes are negligible. In addition, $\sigma _{\phi _{c}}$ exhibits a larger sensitivity to the scene variability, if compared to single-polarization intensity channels, over both slick-free and oil-covered sea surface. This sensitivity is more pronounced at lower AOIs due to the higher noise equivalent sigma zero (NESZ) that affects larger AOIs.

10 pages, 10 figures, 3 tables, In this paper, the synthetic aperture radar (SAR) azimuth cutoff method is thoroughly revised and a new and general implementation is proposed. The key roles of the pixel spacing, the size of the image box, and the texture of the SAR scene are analyzed and optimized in terms of azimuth cutoff (λ c ) estimation. The reliability of the λ c estimation is analyzed by measuring the distance between the measured and fitted autocorrelation functions. This analysis shows that it is of paramount importance to filter unfeasible/unreliable λ c values. To identify those values in an objective way, a criterion that is based on the χ2 test performed over a large data set of Sentinel1 SAR imagery is defined and proven to be effective. The new robust implementation of the λ c estimation at about 1-km grid spacing is then used to produce averaged λ c at about 10-km grid spacing. The performance of the new estimation procedure, analyzed using a λ c -to-wind-speed forward model, is shown to provide improved wind speed retrievals, with a root-mean-square error of 1.8-2 m/s when verified against independent numerical weather prediction model output and scatterometer winds

In this paper, a theoretical and experimental analysis of polarimetric synthetic aperture radar (SAR) architectures is undertaken for sea oil slick observation purposes. Reference is made to the conventional full-polarimetric (FP) SAR that is here contrasted with new-generation polarimetric SAR architectures, known as compact-polarimetric (CP) SAR. Two CP modes are considered, i.e., the hybrid-polarity and π/4 modes, whose measurements are emulated from actual L- and C-band FP SAR data. Polarimetric sea surface scattering is predicted according to an extended version of the Bragg scattering model (X-Bragg) in order to point out the differences exhibited between FP and CP SAR architectures and among CP SAR modes. Theoretical predictions are then contrasted with experiments undertaken on actual polarimetric SAR data collected over well-known oil slicks and weak-damping surfactants. Results confirm model prediction, showing that differences mainly apply when polarimetric features are estimated over slick-free sea surface using different SAR architectures, with the π/4 mode behaving closer to FP SAR. Although CP SAR architectures measure only a subset of the FP information content, they represent an interesting operational alternative for both detecting oil slicks and discriminating them from weak-damping surfactants.

In this letter, fully polarimetric (FP) and compact polarimetric (CP) synthetic aperture radar (SAR) features are investigated over the sea surface. While exhibiting similar trends, subtle differences are observed and investigated here using a new model-based approach. The model indicates that differences between the FP and CP architectures, and among the CP modes, are due to the difference in mapping between the polarimetric observables and the eigenvalues. This is verified using actual FP SAR data and emulated CP SAR measurements.

This paper reviews some significant achievements in the research activity and academic career of Paolo Corona, with particular focus on electromagnetic reverberation theory and measurements. An annotated selection is presented for some of his celebrated publications as well as some lesser well-known unpublished works.Some of his recorded views on issues and directions for future research on reverberation chambers are also included.

The quintessence of electromagnetic fields propagating in complex environments is its stochastic nature. The canonical test facility to emulate such a complex case is the reverberating chamber (RC). In order to design, test, and model the electromagnetic field in an RC, one must consider the vectorial nature of the field. The electromagnetic field within an RC has a random 3-D structure that must be properly taken into account to analyze it. A robust and basis invariant analysis of the randomness of such 3-D field is here undertaken estimating the polarization purity, i.e., the degree of polarization. In this paper, a new approach, based on the decomposition of the 3-D degree of polarization, is exploited to analyze the electromagnetic field within an RC. Experiments, undertaken exploiting the RC of Universita degli Studi di Napoli Parthenope, formerly Istituto Universitario Navale (IUN), provide a first experimental validation of the aforementioned decomposition in the microwave range of frequency. In addition, such decomposition, being able to sort out information related to the stability of the polarization ellipse and of the direction of propagation, is a key tool to analyze the effectiveness of the stirring process within the RC.

In this paper, the standard measurement uncertainty (MU) of the insertion loss (IL) in loaded and unloaded continuous mode stirred reverberation chambers (RCs) in presence of both mechanical and frequency stirring is evaluated. The frequency stirring (FS) is essential to increases the total number of uncorrelated samples in an RC; however, when it is combined to a mechanical continuous stirring, a data preprocessing is necessary to check the total number of non-correlated samples. The methodology proposed in this paper is fast and general, i.e., it can be used for several applications of RCs. Since the loading increases the non-uniformity of fields in RCs and it affects the standard MU of the IL, results are also evaluated under the effect of a load.

We analyze the uncertainty of measurements carried out in a reverberation chamber. The adopted model includes the frequency stirring method and different $K$ -Factor values. Two majorants are proposed to enhance the uncertainty computation of the chamber insertion loss.

In this study, typhoon monitoring is addressed using X-band synthetic aperture radar (SAR) imagery collected by the German TerraSAR-X mission and the Italian COSMO-SkyMed constellation during the typhoon Megi. Geometrical features, rain rate, and wind speed associated with the typhoon are retrieved by the SAR data set. One of the key benefits of the X-band observations relies in their sensitivity to rain that can be exploited to provide an estimate of geometrical features and rain rate by analyzing attenuation bands present in the SAR data. In addition, wind speed is retrieved using a rain-free model based on two geophysical model functions (GMFs) and experimental results show that the nonlinear relationship between normalized radar cross section and wind speed provided by one of the GMFs can be exploited to provide a rough estimate of high wind speeds.

In this paper, performance of different indicators for the profiling of Ultra Wide Band (UWB) wireless propagation channel are analyzed. In particular, the γ-indicator and the kurtosis index k are compared in terms of the standard error. In order to improve the accuracy in the kurtosis case, results of the bootstrap error procedure are also accomplished. Further, an evaluation on the computational time needed for error estimation, is also provided. The comparison is made according to a real set of data derived from UWB measurement campaign accomplished within a modern laboratory/office building in which the two above mentioned indicators have been evaluated.

In this paper, it is shown an enhancement of a previous model on the measurement standard uncertainty (MU) of the insertion loss (IL) in a reverberation chamber (RC) including frequency stirring (FS). Differently from the previous model, the enhanced does not require specific conditions on the parameter to be measured. Such an enhancement is applicable for all usable measurement conditions in RCs. Moreover, a useful majorant is also shown; it is obtained under a weak condition on the coefficient of variation (CV) of the parameter to be measured. Results by measurements support the validity of the proposed enhancement and of the majorant., Comment: 8 pages, 20 figures

The probability density function (PDF) of the quality factor Q of well-stirred mode tuned, source stirred, and mode stirred reverberation chambers (STRCs, SSRCs and MSRCs, respectively) is derived. The approach is based on the volumetric number of independent field samples, and a new physical model is introduced to estimate the ratio between the stored energy and the dissipated power, so that the stirring speed is taken into account for MSRCs. The ergodicity of the spatial-correlation function of the energy density in the chamber volume is initially assumed; in other words, the independent sample number of the energy density, which contributes to the Q , is assumed to initially be constant for each field distribution across the volume. Then, this assumption is relaxed and the theory is enhanced to the case where the size of the independent volumetric samples is considered random, as well as their number. By invoking the central limit theorem, the Q PDF is achieved. It is shown that the Q PDF is basically normal, and its standard deviation decreases with the increasing of the independent variables that contribute to the Q itself. The Doppler effect tends to increase the standard deviation of the Q PDF.

Most of the inverse problems arising in applied electromagnetics come from an underdetermined direct problem, this is the case, for instance, of spatial resolution enhancement. This implies that no unique inverse operator exists; therefore, additional constraints must be imposed on the sought solution. When dealing with microwave remote sensing, among the possible choices, the minimum $p$ –norm constraint, with $1 , allows obtaining reconstructions in Hilbert $(p=2)$ and Banach $(1 subspaces. Recently, it has been experimentally proven that reconstructions in Banach subspaces mitigate the oversmoothing and the Gibbs oscillations that typically characterize reconstructions in Hilbert subspaces. However, no fair intercomparison among the different reconstructions has been done. In this paper, a mathematical framework to analyze reconstructions in Hilbert and Banach subspaces is provided. The reconstruction problem is formulated as the solution of a $p$ –norm constrained minimization problem. Two signals are considered that model abrupt and spot-like discontinuities. The study, undertaken in both the noise-free and the noisy cases, demonstrates that $l^p$ reconstructions for $1 significantly outperform the $l^2$ ones when spot-like discontinuities are considered; when dealing with abrupt discontinuities, $l^2$ and $l^p$ reconstructions are characterized by similar performance; however, $l^p$ reconstructions exhibit oscillations when the background is not properly accounted for.

In this study, hybrid-polarity (HP) architecture is exploited to observe sea oil slicks. HP features are interpreted in terms of sea surface scattering with or without oil slicks, under low-to-moderate wind conditions. They are shown to exhibit a different sensitivity with respect to slick-free, weak-damping slick-covered, and oil-covered sea surfaces. This sensitivity is verified against HP measurements obtained transforming actual L- and C-band quad-polarimetric synthetic aperture radar (SAR) data where both oil slicks and weak-damping look-alikes are present. Experiments demonstrate: 1) the remarkable performance of HP features to both observe oil slicks and distinguishing them from weak-damping look-alikes; 2) the marginal effect played by the sensor's noise floor on HP features performance; 3) the pronounced sensitivity of the HP features to the damping properties of the surfactants; and 4) the comparable performance that characterizes polarimetric entropy derived by HP and conventional polarimetric measurements.

A reconstruction technique, based on the 2-D truncated singular value decomposition, is first proposed to enhance the spatial resolution of radiometer earth observation measurements. The technique is very computer time effective when the kernel is a 2-D tensor product. The key issue regarding the selection of the truncation parameter is addressed by the statistically based generalized cross-validation approach. Experiments undertaken on a data set consisting of both simulated and actual 2-D special sensor microwave imager radiometer measurements show the robustness of the technique against the additive noise and its effectiveness in terms of processing time. A typical 2-D radiometer scene is processed in seconds by a standard PC processor.

In this study, a model based on the generalised-K (GK) distribution is proposed for identifying ultra-wideband (UWB) indoor channel profiles. In particular, an index (γ-index) based on a proper combination of GK parameters is proposed to unambiguously and effectively distinguish among line-of-sight (LOS) and non-LOS propagation conditions. This clear distinction is achieved by defining two non-overlapping sets which correspond to the two well-defined profiles. The technique is user-friendly since it does not call for any complex estimation process. Comparison among the results achieved by both real measurements and IEEE.802.15.4a channel model simulations confirm the soundness of the employed method and the effectiveness of the proposed γ-index.

ScanSAR is a synthetic aperture radar (SAR) acquisition mode particularly suitable to several environmental applications due to its very large swath. This mode, once operated by virtual or real constellations, is able to remarkably reduce the revisit time, and this is of great relevance in all marine applications. Unfortunately, this particular kind of acquisition is affected by an intrinsic phenomenon, called scalloping, that hampers image interpretation, particularly in the case of data acquired over the sea. In this letter, an innovative and computationally efficient postprocessing procedure is presented in order to get rid of scalloping in ScanSAR data. Experiments accomplished over multilook ground-detected SAR COSMO-SkyMed data confirm the physical soundness of the proposed technique.

A physical dual-polarimetric model to observe man-made metallic targets at sea in dual-polarimetric coherent X-band synthetic aperture radar (SAR) data is proposed. The model exploits the intrinsic different symmetry properties of man-made targets and sea surface and is tested over actual StripMap TerraSAR-X HH-HV and VV-VH dual-polarimetric SAR data and colocated ground truth measurements. Then, an operational physically based filter to observe targets at sea is proposed. The filter is very attractive in terms of both detection performances and processing time. A typical SAR scene is processed in seconds by a conventional PC processor.

In this paper, test study on low-cost civil engineering construction material is presented. In fact, in several civil constructions the strategy is to build up to flrst \fence" to EMI that limits interferences while using only in some limited areas high-cost ad hoc shielding material. The materials used in this study are tested at the Universitµa di Napoli Parthenope, formerly Istituto Universitario Navale (IUN) Reverberating Chamber (RC) according to a nested approach. Tests are made in the frequency range from 2 to 18GHz and show that low-cost materials are able to achieve about 16dB of shielding efiectiveness (SE) in contrast to ad hoc materials that show about 50dB in SE.

A dual-polarimetric model to exploit X-band COSMO-SkyMed (CSK) dual-polarimetric PingPong mode synthetic aperture radar (SAR) data for metallic target observation purposes is first developed. The model relates the correlation between the copolarized channels, in case of sea surface with and without metallic targets, to the time offset between bursts related to the HH and VV polarimetric channels. Following this theoretical rationale, a constant false alarm rate (CFAR) approach is implemented to first exploit CSK PingPong full-resolution SAR data for target observation purposes. Experiments undertaken over a large data set of COSMO-SkyMed single look complex slant (SCS) PingPong HH/VV SAR data demonstrate the physical soundness of the approach and its effectiveness from an operational viewpoint. A whole CSK SAR scene is processed in about 10 s. Furthermore, the dual-polarization approach is also compared with a conventional single-polarization CFAR one and it is shown to perform best.

A new methodology to estimate the growth stages of agricultural crops using the time series of polarimetric synthetic aperture radar (PolSAR) images is proposed. The methodology is based on the complex Wishart classifier and both phenological intervals and training areas are identified measuring the distances among polarimetric covariance matrices obtained from the time series of PolSAR data. Consequently, the computation of PolSAR features, which is the main step of state-of-the-art methods, is no longer needed, and the proposed approach can be applied in the same way to any crop type. Experiments undertaken on a dense time series of fully polarimetric C-band RADARSAT-2 images, collected at incidence angles ranging from 23° to 39°, in ascending/descending orbit passes, demonstrate that the proposed methodology can be successfully applied to retrieve the phenological stages of four different crop types. In addition, the effect of combining beams corresponding to different sensor's configurations has been evaluated, showing that it affects the retrieval accuracies. Validation with ground data shows the following: overall accuracy is between 54% and 86%; producer's accuracy (PA) and user's accuracy (UA) range between 21% and 100% and between 33% and 100%, respectively. This work was supported in part by the Spanish Ministry of Economy and Competitiveness (MINECO) and EU FEDER under Projects TEC2011-28201-C02-02 and TIN2014-55413-C2-2-P.

In this paper, target at sea detection is addressed using hybrid-polarity (HP) synthetic aperture radar (SAR) architecture. Wave polarimetry concepts are used to define HP features that are used to observe targets at sea. The sensitivity of HP features to both targets and the surrounding environment is analyzed through a novel objective norm, namely the Relative Sensitivity for Polarimetric Features (RSPolF) index. Detection performance is evaluated by the novel Dependency of Sea state and Target (DoST) surface characteristics metric, and by the well-known Figure of Merit (FoM). Experiments undertaken on HP measurements emulated from Radarsat-2 and ALOS-PALSAR full-polarimetric actual SAR data demonstrate the effectiveness of the proposed HP approach and the different sensitivity of HP features to targets and background sea characteristics. Following those results, a ranking of the HP features performance is proposed which mainly highlights that HP features complement each other in the detection process. Finally, a constant false alarm rate (CFAR) approach is proposed to exploit two HP features for target detection in an unsupervised way.

In this paper, a new paradigm for coherent microwave polarimetric remote sensing observation of man-made metallic targets at sea is presented and demonstrated over real polarimetric synthetic aperture radar (SAR) data. It is based on the different symmetry properties of the sea and of the man-made targets. The rationale relies on physical principles instead of standard image processing. Hence, a simple and very effective filter to observe man-made metallic targets at sea by full-resolution dual-polarized SAR data is developed. The technique is compared to a classic polarimetric approach, namely the polarimetric cross-entropy (PCE) constant false alarm rate (CFAR), and it is shown to perform best. Experiments, undertaken over a large data set of single look complex (SLC) L-band ALOS-PALSAR and C-band RADARSAT-2 full-polarimetric SAR data, demonstrate the physical soundness of the theory and the effectiveness of the approach from an operational viewpoint.

Within the National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Administration, multiplatform synthetic aperture radar (SAR) imagery is being used to aid post hurricane and postaccident response efforts in the Gulf of Mexico, such as in the case of the recent Deepwater Horizon oil spill. The main areas of interest related to such disasters are the following: (1) to identify oil pipeline leaks and other oil spills at sea and (2) to detect man-made metallic targets over the sea. Within the context of disaster monitoring and response, an innovative processing chain is proposed to observe oil fields (i.e., oil spills and man-made metallic targets) using both Land C-band full-resolution and fully polarimetric SAR data. The processing chain consists of two steps. The first one, based on the standard deviation of the phase difference between the copolarized channels, allows oil monitoring. The second one, based on the different symmetry properties that characterize man made metallic targets and natural distributed ones, allows man made metallic target observation. Experiments, accomplished over single-look complex L-band Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) and C-band RADARSAT-2 fully polarimetric SAR data gathered in the Gulf of Mexico and related to the Deepwater Horizon accident, show the effectiveness of the proposed approach. Furthermore, the proposed approach, being able to process both Land C-band fully polarimetric and full resolution SAR measurements, can take full benefit of both the ALOS PALSAR and RADARSAT-2 missions, and therefore, it allows enhancing the revisit time and coverage which are very critical issues in oil field observation.

This paper enhances the new nested chambers shielding effectiveness approach proposed by Holloway. The enhanced model considers the multiple interactions between the two chambers and nonreciprocal samples. Results show that the enhancement is remarkable when the two chambers are tightly coupled and the shielding effectiveness is not marginal.

In this letter, a fully polarimetric electromagnetic model for sea surface Mueller matrix is exploited to characterize the scattering from oil and biogenic slicks, under low-to-moderate wind conditions. The model predicts a completely different scattering mechanism for oil-covered and oil-free sea surface, while biogenic slicks are indistinguishable from sea surface in terms of polarimetric scattering. Following this theoretical rationale, a simple and very effective filtering technique is proposed for synthetic aperture radar (SAR) sea oil slick observation. Experiments, accomplished over C-band multilook complex SIR-C/X-SAR data, show the effectiveness of the proposed model and the capabilities of the filter to both observe oil slicks and distinguish them from biogenic look-alikes.

Synthetic aperture radar (SAR) ship detection is an important application in the context of environment and security monitoring. It allows monitoring traffic, fisheries, and associating ships with oil discharge over wide areas with high spatial resolution almost independently from weather conditions and both day and night time. Since full-resolution SAR images are heavily affected by the presence of speckle, ship detection algorithms generally employ speckle reduced SAR images at the expense of a degradation of the spatial resolution. A new physical approach, which considers ships as dominant scatterers and, therefore, responsible for a strong and coherent backscattered signal, is here proposed. Based on this rationale, a new simple and very effective filtering technique, which is able to process full-resolution SAR images, has been conceived and implemented. Experiments, accomplished over C-band European Remote Sensing satellite (ERS) 1/2 single-look complex SAR images, show the effectiveness of the proposed approach.

Interferometric synthetic aperture radar processing requires interpolating a slave image onto a master one. Since the signals requiring interpolation are limited in both time and bandwidth, the Knab sampling window provides an almost optimal and viable interpolation kernel. Its performance in terms of coherence preservation and interferometric phase error as a function of the number of retained samples and oversampling factor are shown.

A study on sea oil spill observation by means of polarimetric synthetic aperture radar (SAR) data is accomplished. It is based on the use of a polarimetric constant false alarm rate filter to detect dark patches over SAR images. Then, the target decomposition theorem is exploited to distinguish oil spills and look-alikes. Experiments are conducted on polarimetric SAR data acquired during the SIR-C/X-SAR mission on October 1994. The data were processed and calibrated at the Jet Propulsion Laboratory, National Aeronautics and Space Administration. Results show that the new polarimetric approach is able to assist classification

A new physically based speckle model for marine single-look complex (SLC) synthetic aperture radar (SAR) images is here presented and investigated. The model allows using full-resolution SAR images instead of multilook SAR images, in which, at the expense of a coarser spatial resolution, the speckle is mitigated. The model is based on the three-parameters generalized-K (GK) probability density function (pdf). GK pdf is a suitable physically-based speckle model for marine SAR images ensuring a continuous and physically consistent transition among different scattering scenarios. This speckle model embodies Rayleigh, K, and Rice scattering scenes which are typical of marine scenes. The use of the three parameters, related to the GK pdf ones, is able to highlight the presence of both low backscattering areas and areas in which a small dominant scatterer is present. This is operationally interesting in SAR oil spill detection procedures.

A simple innovation that enables a faster convergence rate of iterative gradient-like descent approaches is proposed and applied to linear image reconstruction problems from irregular sampling. The key idea is to reduce the amount of regularization effects of the conventional Tikhonov functional by introducing a negative seminorm penalty term, whose role is to speed up the convergence without reducing the reconstruction accuracy. The method is employed to enhance the spatial resolution of microwave remotely sensed products. First experiments, undertaken on simulated radiometer data, demonstrate that the technique significantly increases the convergence rate, halving the number of iterations when applied to speed up the basic and widely used Landweber method.

International audience; In this paper, a new computer-time effective iterative method is proposed to enhance the spatial resolution of microwave radiometer data in both Hilbert and Banach spaces. The reconstruction method is based on the conjugate gradient (CG) method. CG is a well-known method in electromagnetics, where it is commonly used to address inverse problems in Hilbert spaces. However, the method has never been applied to inverse problems related to spatial resolution enhancement of microwave remotely sensed measurements. In this paper, CG is adapted to the microwave radiometer case and exploited to reconstruct the brightness field at enhanced spatial resolution. Then, CG is, for the first time, extended to Banach spaces by means of duality maps and then applied to enhance the radiometer spatial resolution. Experiments undertaken on both simulated and actual radiometer data confirm the soundness of the proposed approach in Banach spaces and demonstrate that CG is able to provide a reconstruction accuracy similar to the conventional Landweber method, but with a significantly reduced processing time.

The measurement of the absorption cross section (ACS) is one of the applications of a reverberation chamber. In this letter, a statistical analysis of the uncertainty of ACS measurements is shown. The achieved model enhances the one already present in the literature and is done differently. Measurements show the importance of the uncertainty component connected to the position of the antennas and/or of the absorbing sample and how it is reduced so that the simple model based only on independent samples can be effectively used.

In this study, a simple model for the autocorrelation function (ACF) within a reverberating chamber (RC) is developed and verified. In particular, in a well-stirred RC when n mechanical stirrers operate, the ACF of the total field is given by the product of n ACFs obtained when the n stirrers are singularly operated. Hence, a parameterisation of the ACF is accomplished. Accordingly, it is possible to parameterise the coherence time, T C, of the RC emulated wireless propagation channels. Experiments accomplished at the RC of the Universita degli Studi di Napoli Parthenope, formerly Istituto Universitario Navale, confirm the soundness of the proposed model and its operational effectiveness.

In this paper, a physical approach to support oil spills observation over synthetic aperture radar (SAR) images is presented. Electromagnetic model is based on an enhanced damping model that takes into account oil viscoelastic properties and wind speed. As a matter of fact, a multisensor approach is considered and a constant false alarm rate (CFAR) filter is used to minimize speckle effect. A set of experiments is presented and discussed. They show that oil spill processing is effective over single-look SAR images using mean input data.