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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 study, the azimuth cut-off method, typically used for SAR moderate wind speed estimation purposes, is analyzed under high wind regimes. Firstly, the importance of the pixel spacing, the size of the boxes selected for Synthetic Aperture Radar (SAR) image partitioning and the image texture in terms of homogeneities are discussed by considering their influence on the azimuth cut-off (λc) estimation. Secondly, a quality control analysis of the reliability of λc is carried out by evaluating the distance between the autocorrelation functions (ACF) and their correspondent fittings. This analysis points out the importance of filtering out the unreliable and unfeasible λc values in order to improve the wind speed estimation. The quality control procedure is based on a x2 test, applied on a large Sentinel-1A dataset. The soundness of the test is verified by an increment in terms of correlation between λc estimations and wind speed values. This approach is, then, applied under high wind regimes, i.e., tropical cyclones.

In this study, we provide a summary of research advances in the field of maritime target detection using DP (dual-polarimetric) SAR (Synthetic Aperture Radar) imagery, accomplished during the European and China collaboration in the framework of the Dragon-4 program ID 32235. The main innovative contribution is twofold: ①We addressed ship detection proposing an improved GP-PNF (Geometrical Perturbation-Polarimetric Notch Filter), termed as IGP-PNF, that is characterized by a new feature vector that includes three new scattering features; ②We addressed oil platform detection by contrasting single-polarization SAR methods with polarimetric ones in order to quantify the extra- benefit carried on polarimetric information. The proposed theoretical framework is tested against actual multi-polarization SAR data. In particular, ship detection methods are verified against a Sentinel-1 SAR scene where a large number of ships is present; while, oil platform detection is discussed using TerraSAR-X SAR data. Experimental analysis shows that: ①The IGP-PNF method performs best in terms of clutter-to-target ratio; ②Coherent polarimetric information significantly outperforms single-polarization SAR measurements in highlighting targets in challenging cases.

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.

This study deals with coastline extraction using multipolarization spaceborne synthetic aperture radar (SAR) imagery acquired over coastal intertidal areas. The latter are very challenging environments where mud flats lead to a large variability of normalized radar cross section, which may trigger a significant number of false edges during the extraction process. The performance of SAR-based coastline extraction methods that rely on a joint combination of multipolarization information (either single- or dual-polarization metrics) and speckle filtering (either local and nonlocal approaches) are analyzed using global positioning system (GPS) samples and colocated SAR imagery collected under different incidence angles. Our test site is an intertidal zone with a wetland (i.e., salt marsh) in the Solway Firth, south-west along the Scottish-English border. Experimental results, obtained processing a pair of RadarSAT-2 full-polarimetric and a pair of Sentinel-1 dual-polarimetric SAR imagery augmented by colocated GPS samples, show that: first, the multipolarization information outperforms the single-polarization counterpart in terms of extraction accuracy; second, among the single-polarization channels, the cross-polarized one performs best; third, both single- and dual-polarization methods perform better when nonlocal speckle filtering is applied; fourth, the joint combination of nonlocal speckle filter and dual-polarization information provides the best accuracy; and finally, the incidence angle plays a role in the extraction accuracy with larger incidence angles resulting in the best performance when dual-polarization metric is used.

To monitor polar regions is of paramount importance for climatological studies. Climate change due to anthropogenic activities is inducing global warming that, for example, has resulted in glacier melting. This has had a significant impact on sea levels and ocean circulation. In this study, the temporal trend of the marine-terminated d’Iberville glacier (Ellesmere Island, Canada) is analysed using C-band synthetic aperture radar satellite imagery collected by the Radarsat-2 and Sentinel-1 missions. The data set consists of a time series of 10 synthetic aperture radar data collected from 2010 to 2022 in dual-polarimetric imaging mode, where a horizontally polarised electromagnetic wave was transmitted. An automatic approach based on a global threshold constant false alarm rate method is applied to the single- and dual-polarisation features, namely the HH-polarised normalised radar cross-section and a combination of the HH- and HV-polarised scattering amplitudes, with the aim of extracting the ice front of the glacier and, therefore, estimating its behaviour over time. Independent collocated satellite optical imagery from the Sentinel-2 multi-spectral instrument is also considered, where available, to support the experimental outcomes. The experimental results show that (1) the HH-polarised normalised radar cross-section achieved better performance with respect to the dual-polarised feature, especially under the most challenging case of a sea-ice infested sea surface; (2) when the HH-polarised normalised radar cross-section was considered, the ice front extraction methodology provided a satisfactory accuracy, i.e., a root mean square error spanning from about 1.1 pixels to 3.4 pixels, depending on the sea-surface conditions; and (3) the d’Iberville glacier exhibited, during the study period, a significant retreat whose average surface velocity was 160 m per year, resulting in a net ice area loss of 2.2 km2 (0.18 km2 per year). These outcomes demonstrate that the d’Iberville glacier is behaving as most of the marine-terminated glaciers in the study area while experiencing a larger ice loss.

In this study, multi-polarization Synthetic Aperture Radar (SAR) features extracted from Sentinel-1 C-band SAR measurements are used to identify wildfires and to classify burn severity. SAR features include co- and cross-polarized normalized radar cross sections and the total backscattered power, namely the SPAN. The test case refers to the wildfire that affected about 10 km2 in Tuscany region (Central Italy) during September 2018. Experiments, undertaken on actual SAR data, collected before and after the considered wildfire, demonstrate the soundness of the proposed approach and the different sensitivity of the multi-polarization backscattering features to burn severity.

In this study, a new antenna pattern deconvolution method to enhance the spatial resolution of multi -channel microwave radiometer (MWR) measurements is developed. This technique, based on a conventional gradient-like iterative method, utilizes the information contained in a high-frequency channel to enhance the spatial resolution of the lower-frequency channel in a data-fusion fashion. The physical idea consists of initializing the gradient -like inversion scheme using higher frequency details that are filtered out by the system measurement function. Experiments, performed on a dataset that includes both simulated and actual radiometer measurements, show that the proposed technique allows outperforming the conventional gradient method, while being very robust with respect to artifacts that could be induced by the higher frequency channel.

In coastal areas, the wind vector at sea is one of the most important geophysical variable of interest. Wind field information is crucial for navigation, green energy production, fishing, etc. Nonetheless, to obtain distributed and accurate sea wind information in coastal areas is a challenging task that cannot be achieved by buoys, anemometers or satellite sensors as lidars and scatterometers. Hence, in this study, the behavior of sea wind field is analyzed over the selected test site, i. e., the Gulf of Naples (Italy, Mediterranean Sea) using level-2 ocean products obtained by the C-band Synthetic Aperture Radar (SAR) on board of the European Space Agency mission Sentinel-1. The latter are compared with space/time co-located wind vectors obtained by the Weather and Research Forecasting (WRF) model. Preliminary experimental results indicate that there is a fairly good agreement between wind vectors estimated from SAR and the ones predicted by the WRF model. They suggest that a moderate eastern wind blowed over the study area in the considered period.

In this study, dual-polarization (DP) C-band Sentinel-1 SAR imagery are processed to generate a damage map related to an earthquake damaged area. A DP change detection scheme, which uses a pair of SAR imagery collected before and after the earthquake, is used. Finally, to quantify the levels of damage a decision tree procedure is exploited. The damaged area refers to the city of Amatrice and its surroundings that were devastated by the earthquake that hit central Italy on 24 August 2016. To generate the damage map and to verify it, ground information provided by Istituto Nazionale di Ge-ofisica e Vulcanologia (INGV) is processed to generate a new index, termed as Weighted Damage Index (WDI). Numerical results show that an accuracy of about 60% can be obtained that confirms the soundness of the proposed approach.

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.

This study addresses the spatial resolution enhancement of synthetic microwave radiometer observations obtained by the Soil Moisture Active Passive (SMAP) L-Band Radiometer. An antenna pattern deconvolution method is used together with an iterative regularization scheme to reconstruct the brightness field at enhanced spatial resolution. Results obtained processing both synthetic and actual SMAP measurements show that sharper edges and coastlines can be reconstructed in a very effective way.

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.

Satellite synthetic aperture radar (SAR) is a unique tool to collect measurements over sea surface but the physical interpretation of such data is not always straightforward. Among the different sea targets of interest, low-backscattering areas are often associated to marine oil pollution even if several physical phenomena may also result in low-backscattering patches at sea. In this study, the effects of low-backscattering areas of anthropogenic and natural origin on the azimuth autocorrelation function (AACF) are analyzed using VV-polarized SAR measurements. Two objective metrics are introduced to quantify the deviation of the AACF evaluated over low-backscattering areas with reference to slick-free sea surface. Experiments, undertaken on six Sentinel-1 SAR scenes, collected in Interferometric Wide Swath VV+VH imaging mode over large low-backscattering areas of different origin under low-to-moderate wind conditions (speed ≤ 7 m/s), spanning a wide range of incidence angles (from about 30∘ up to 46∘), demonstrated that the AACF evaluated within low-backscattering sea areas remarkably deviates from the slick-free sea surface one and the largest deviation is observed over oil slicks.

This study analyzes the ability of polarimetric Synthetic Aperture Radar (PolSAR) measurements to quantify post-earthquake damages. To achieve this goal, a twofold task is addressed: on one side a ...