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We present a novel configuration for an axial virtual cathode oscillator (Vircator) operating in the C-band and designed for high output power applications. In order to enhance the efficiency, we have employed a geometry with up to seven reflectors along the drift space. While in previous research works this optimization process has been performed only varying the reflectors radii while using a fixed distance between reflectors,in our work we propose an optimization in terms of both reflectors radii and distances. Our optimized structure for the axial Vircator is able to provide an efficiency up to 15.6% and an output power of 1.6 GW in the C-band, with a working voltage of 510 kV and a cathodic current of 24 kA.

The retrieval of soil moisture information with spatially and temporally high resolution from Synthetic Aperture Radar (SAR) observations is still a challenge. By using multi-orbit Sentinel-1 C-band time series, we present a novel approach for estimating volumetric soil moisture content for agricultural areas with a temporal resolution of one to two days, based on a short-term change detection method. By applying an incidence angle normalization and a Fourier Series transformation, the effect of varying incidence angles on the backscattering signal could be reduced. As the C-band co-polarized backscattering signal is prone to vegetational changes, it is used in this study for the vegetational correction of its related backscatter ratios. The retrieving algorithm was implemented in a cloud-processing environment, enabling a potential global and scalable application. Validated against eight in-situ cosmic ray neutron probe stations across the Rur catchment (Germany) as well as six capacitance stations at the Apulian Tavoliere (Italy) site for the years 2018 to 2020, the method achieves a correlation coefficient of R of 0.63 with an unbiased Root Mean Square Error of 0.063 m3/m3.

This paper presents a novel slotted array for dual-band and circular-polarized applications. Two different propagation modes within a Substrate Integrated Waveguide (SIW), TE10 and TE20, feed at the same time two pairs of slots, aimed at different frequency bands. The pairs are properly placed to be illuminated by an only propagation mode, whereas the magnetic field of the other propagation mode presents a null. Unlike many dual-band slot arrays, this novel antenna holds the same beam tilt for both frequency bands by a new method, which is only feasible through the use of two propagation modes. A dual-mode transition, based on a double microstrip input, allows to excite both propagation modes within the SIW, and it can be fed by a novel single layer dual-band phase shifter with a different shift at each frequency. A square patch is placed over each pair of slots to increase the coupled energy per element, resulting in a low polarization loss and high performance compact antenna at 3.5GHz and 6GHz for dual-band TX/RX systems at C-Band.

A wideband circularly-polarized (CP) monopole antenna is implemented. It comprises of the single P-shaped radiator fed by the L-shaped microstrip transmission line with edged ground plane on the reverse side of the square substrate. The optimization of the radiator and feed gap parameters helps in enhancing impedance bandwidth (IBW) and axial ratio bandwidth (ARBW). The measured IBW is of 5.65 GHz (3.9–9.55 GHz, 84.01%, center resonating frequency frc = 6.725 GHz) and the simulated IBW is of 5.73 GHz (3.8–9.53 GHz, 85.97%, frc = 6.6 GHz), respectively. The corresponding simulated ARBW is of 1.47 GHz (6.62–8.09 GHz, 19.99%, CP resonating frequency fCP = 7.35 GHz) inside measured and simulated IBW curves. The peak gain is maximum at the frequency of 7.76 GHz, and it is equal to 5.01 dBi. Simulated results using Ansys Electronics Desktop 2020R1 match well with measurements. The optimized dimension of the proposed compact antenna is of 20×20×1.6 mm3, with 57.49% reduction in size. It can be suitable for the applications in C-band wireless communication.

Passive Optical Networks (PON), able to operate at 50 Gbps per wavelength (), are under development and standardization, based on intensity-modulation (IM) and direct-detection (DD) systems. The next step in PON evolution will be driven by 5G/6G fronthauling capacity demands, and will require the development of 100 Gbps/ (and beyond) systems, which poses big challenges if maintaining the DD-format. In this contribution, we analyze a 100 Gbps/ PON architecture able to preserve the IM-DD approach at the Optical Network Unit (ONU), placing the complexity at the Optical Line Terminal (OLT), thanks to Digital Signal Processing (DSP). We experimentally demonstrate a 100 Gbps/ transmission using this architecture in the downstream (DS) direction. Chromatic dispersion digital pre-compensation (CD-DPC) in combination with an IQ Mach-Zehnder Modulator (IQ-MZM) is used at the transmitter (TX). Keeping the ONU DSP as simple as possible, as compared with current DSP proposals for 50 Gbps/ PON, is another main goal of this work. Adaptive equalization (AEQ) is used to correct for linear impairments, in addition to digital non-linear correction (NLC) at the receiver (RX). We compare two NLC approaches: a full Volterra Non-Linear Equalizer (VNLE) and a simpler NLC technique based on a square-root like function (SQRT). Operation over standard single-mode fiber (SMF) in C-band, achieving reaches from 0 km to 100 km and Optical Path Loss (OPL) values higher than 29 dB, are shown. The analyzed proposal is directly applicable to Terabit-capable wavelength division multiplexing (WDM)-PON, and can be extended to very high-speed Time Division Multiplexing (TDM)-PON and TWDM-PON, with some modifications discussed here.

Very high-resolution (∼10–100 m) surface soil moisture (SM) observations are important for applications in agriculture, among other purposes. This is the original goal of the S2MP (Sentinel-1/Sentinel-2-Derived Soil Moisture Product) algorithm, which was designed to retrieve surface SM at the agricultural plot scale by simultaneously using Sentinel-1 (S1) backscatter coefficients and Sentinel-2 (S2) NDVI (Normalized Difference Vegetation Index) as inputs to a neural network trained with Water Cloud Model simulations. However, for many applications, including hydrology and climate impact assessment at regional level, large maps with a high resolution (HR) of around 1 km are already a significant improvement with respect to most of the publicly available SM datasets, which have resolutions of about 25 km. In this study, the S2MP algorithm was adapted to work at 1 km resolution and extended from croplands to herbaceous vegetation types. A target resolution of 1 km also allows the evaluation of the interest in using NDVI derived from Sentinel-3 (S3) instead of S2. Two sets of SM maps at 1 km resolution were produced with S2MP over six regions of ∼104 km2 in Spain, Tunisia, North America, Australia, and the southwest and southeast regions of France for the whole year of 2019. The first set was derived from the combination of S1 and S2 data (S1 + S2 maps), while the second one was derived from the combination of S1 and S3 (S1 + S3 maps). S1 + S2 and S1 + S3 SM maps were compared to each other, to those of the 1 km resolution Copernicus Global Land Service (CGLS) SM and Soil Water Index (SWI) datasets, and to those of the Soil Moisture Active Passive (SMAP) + S1 product. The S2MP S1 + S2 and S1 + S3 SM maps are in very good agreement in terms of correlation (R≥0.9), bias (≤0.04 m3 m−3), and standard deviation of the difference (SDD≤0.03 m3 m−3) over the six domains investigated in this study. In a second step, the S1 + S3 S2MP maps were compared to the other HR maps. S1 + S3 SM maps are well correlated to the CGLS SM maps (R∼0.7–0.8), but the correlations with respect to the other HR maps (CGLS SWI and SMAP + S1) drop significantly over many areas of the six domains investigated in this study. The highest correlations between the HR maps were found over croplands and when the 1 km pixels have a very homogeneous land cover. The bias among the different maps was found to be significant over some areas of the six domains, reaching values of ±0.1 m3 m−3. The S1 + S3 maps show a lower SDD with respect to CGLS maps (≤0.06 m3 m−3) than with respect to the SMAP + S1 maps (≤0.1 m3 m−3) for all the six domains. Finally, all the HR datasets (S1 + S2, S1 + S3, CGLS, and SMAP + S1) were also compared to in situ measurements from five networks across five countries, along with coarse-resolution (CR) SM products from SMAP, SMOS, and the European Space Agency Climate Change Initiative (CCI). While all the CR and HR products show different bias and SDD, the HR products show lower correlations than the CR ones with respect to in situ measurements. The discrepancies in between the different HR datasets, except for the more simple land cover conditions (homogeneous pixels with croplands) and the lower performances with respect to in situ measurement than coarse-resolution datasets, show the remaining challenges for large-scale HR SM mapping.

Vegetation optical depth (VOD), as a microwave-based estimate of vegetation water and biomass content, is increasingly used to study the impact of global climate and environmental changes on vegetation. However, current global operational VOD products have a coarse spatial resolution (~25 km), which limits their use for agriculture management and vegetation dynamics monitoring at regional scales (1–5 km). This study aims to retrieve high-resolution VOD from the C-band Sentinel-1 backscatter data over a grassland of the Heihe River Basin in northwestern China. The proposed approach used an analytical solution of a simplified Water Cloud Model (WCM), constrained by given soil moisture estimates, to invert VOD over grassland with 1 km spatial resolution during the 2018–2020 period. Our results showed that the VOD estimates exhibited large spatial variability and strong seasonal variations. Furthermore, the dynamics of VOD estimates agreed well with optical vegetation indices, i.e., the mean temporal correlations with normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and leaf area index (LAI) were 0.76, 0.75, and 0.75, respectively, suggesting that the VOD retrievals could precisely capture the dynamics of grassland.

Feature extraction techniques play an essential role in classifying and recognizing targets in synthetic aperture radar (SAR) images. This article proposes a hybrid feature extraction technique based on convolutional neural networks and principal component analysis. The proposed method is used to extract features of oil rigs and ships in C-band synthetic aperture radar polarimetric images obtained with the Sentinel-1 satellite system. The extracted features are used as input in the logistic regression (LR), support vector machine (SVM), random forest (RF), naive Bayes (NB), decision tree (DT), and k-nearest-neighbors (kNN) classification algorithms. Furthermore, the statistical tests of Kruskal-Wallis and Dunn were considered to show that the proposed extraction algorithm has a significant impact on the performance of the classifiers. © 2022 SPIE. open access

This study investigates the potential of L- and C- bands Polarimetric Synthetic Aperture Radar (PolSAR) data to monitor soil moisture over the forested sites of SMAP Validation Experiment 2012 (SMAPVEX12). The optimal backscattering coefficients and polarimetric parameters to characterize the soil moisture were determined based on L-band Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), C-band RADARSAT-2, and ground measurements composed of soil and vegetation parameters collected during SMAPVEX12. Linear and circular backscattering coefficients (σ0) and polarimetric parameters such as correlation coefficients (ρHHVV) and phase difference (φHHVV) between HH and VV, pedestal height (PH), entropy (H), anisotropy (A), α angle, surface (Ps), and double bounce (Pd) powers were used to develop the relationships with soil moisture. The analysis of these relationships shows that over the forested sites of SMAPVEX12: (a) at L-band several optimal backscattering coefficients and polarimetric parameters allow the monitoring of soil moisture, particularly the linear and circular σ0 (r = 0.60–0.96), Ps (r = 0.59–0.84), Pd (r = 0.60–0.82), ρHHHV_30°, ρVVHV_30°, φHHHV_30° and φHHVV_30° (r = 0.56–0.81). However, compared to the results obtained with σ0, there is no added value of the polarimetric parameters for soil moisture retrievals. (b) at C-band, only a few polarimetric parameters φHHHV, φVVHV, and φHHVV are correlated with soil moisture (r = ~0.90). They can contribute to soil moisture retrievals over forested sites when L-band data are not available.

This work presents a dual-wavelength C-band erbium-doped fiber laser assisted by an artificial backscatter reflector. This fiber-based reflector, inscribed by femtosecond laser direct writing, was fabricated into a single mode fiber with a length of 32 mm. The dual-wavelength laser obtained, centered at 1527.7 nm and 1530.81 nm, showed an optical signal-to-noise ratio over 46 dB when pumped at 150 mW. Another feature of this laser was that the power difference between the two channels was just 0.02 dB, regardless of the pump power, resulting in a dual emission laser with high equalization. On the other hand, an output power level and a central wavelength instability as low as 0.3 dB and 0.01 nm were measured, in this order for both channels. Moreover, the threshold pump power was 40 mW. Finally, the performance of this dual-wavelength fiber laser enhanced with a random reflector for sensing applications was studied, achieving the simultaneous measurement of strain and temperature with sensitivities around 1 pm/µε and 9.29 pm/°C, respectively. This work is part of the projects PID2019-107270RB, funded by MCIN/AEI/10.13039/ 501100011033 and FEDER 'A way to make Europe', and PDC2021-121172 funded by MCIN/AEI/10.13039/ 501100011033 and European Union 'Next generation EU'/PTR, the Ministerio de Educación, Cultura y Deporte of Spain (PhD grant FPU2018/02797).

Discrimination of mangrove stage changes is useful for the conservation of this valuable natural resource. However, present-day optical satellite imagery is not fully reliable due to its high sensitivity to weather conditions and tidal variables. Here, we used the Vertical Transmit—Vertical Receive Polarization (VV) and Vertical Transmit—Horizontal Receive Polarization (VH) backscatter from the same and multiple-incidence angles from Sentinel-1 SAR C-band along with Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Moisture Index (NDMI), Normalized Difference Red Edge (NDVIRE) and Chlorophyll Index Green (CIGreen) from the optical satellite imageries from Sentinel-2 to discriminate between the changes in disturbance, recovery, and healthy mangrove stages in Samut Songkhram province, Thailand. We found the mean NDVI values to be 0.08 (±0.11), 0.19 (±0.09), and −0.53 (±0.16) for the three stages, respectively. We further found their correlation with VH backscatter from the multiple-incidence angles at about −17.98 (±2.34), −16.43 (±1.59), and −13.40 (±1.07), respectively. The VH backscatter from multiple-incidence angles was correlated with NDVI using Pearson’s correlation (𝑟2 = 0.62). However, Pearson’s correlation of a single plot (ID2) of mangrove stage change from disturbance to recovery, and then on to the healthy mangrove stage, displayed a 𝑟2 of 0.93 (p value is less than 0.0001, n = 34). This indicated that the multitemporal Sentinel-1 C-band backscatter and Sentinel-2 data could be used to discriminate mangrove stages, and that a reduced correlation to significant observations was the result of variations in both optical and SAR backscatter data.

This paper presents the design of a flat-panel metasurface reflectarray antenna fed by a circular horn antenna for satellite applications. A metasurface-based reflectarray antenna is similar to a flat-panel reflector and is characterized by a reflection angle adjustment that is free from the well-known Snell’s law. This was done by compensating the angle of the incident wave using the structure of each unit cell. A unit cell of the designed metasurface is composed of a dual-ring resonator. Many satellites use a reflectarray antenna due to its flat-panel structure and the capability of steering the reflection angle of the incident wave. This paper presents the detailed design procedure using a commercial 3D EM simulator and the operation principle of the flat-panel metasurface reflectarray antenna, including the simulation setup, design environment and automation. The proposed design method is scalable to any EM solvers for numerical analysis. A reflectarray composed of a 16 × 16-unit cell array at 5.8 GHz (C-band) was designed and validated by measurement as a proof of concept. It is excited by a low-cost linearly polarized circular horn cantenna. The measured antenna gain and radiation patterns show good agreement with the simulation. The measured antenna gain of the reflectarray was 22.4 dBi (cross-pol suppression level: 36 dB), and the reflection angle was 15° at normal incidence.

Wind wave-induced artifact surface velocity (WASV) is an important component of the sea surface motions detected by synthetic aperture radar (SAR) systems. Understanding the characteristics of the interference of WASV on SAR current velocity estimates is necessary to improve the accuracy of retrievals. In this study, we assessed and analyzed the sensitivity of WASV in C-band along-track interferometric (ATI) SAR to radar configuration, wind field, swell field, and a wave spectrum model. Results showed that the influence of wind speed on WASV increased with the current velocity. The swell also affected WASV, especially at higher wind speeds; WASV was more strongly influenced by swell amplitude than by swell wavelength. In terms of radar configurations, results showed that VV polarization was more suitable than HH polarization in the estimation of WASV. The interference of WASV was minimal at moderate incidence angles (around 40°), and an appropriate ATI baseline selection was also given. The WASV was more strongly influenced by sea states than by the wave spectrum model or by a spreading function. The findings of this study improve our understanding of WASV and provide a reference for the design of future ATI SAR current measurement instruments and projects.

SOA-based multiband OADMs are experimentally assessed in the context of providing optical transparency between metro aggregration nodes and far-edge OLTs. Results show lossless and error-free opetation with penalties ≤ 4dB for up to 3 nodes.

A compact triple-band operation ultra-wideband (UWB) antenna with dual-notch band characteristics is presented in this paper. By inserting three metamaterial (MTM) square split-ring resonators (MTM-SSRRs) and a triangular slot on the radiating patch, the antenna develops measured dual-band rejection at 4.17–5.33 GHz and 6.5–8.9 GHz in the UWB frequency range (3–12 GHz). The proposed antenna offers three frequency bands of operation in the UWB range, which are between 3–4.17 GHz (~1.2 GHz bandwidth), 5.33–6.5 GHz (~1.17 GHz bandwidth), and 8.9–12 GHz (~3.1 GHz bandwidth), respectively. The higher resonating frequency band can be tuned/controlled by varying the width of the triangle slot, while the medium operational band can be controlled by adjusting the width of the SSRR slot. Initially, the simulated S-parameter response, 2D and 3D radiation patterns, gain, and surface current distribution of the proposed UWB inverted triangular antenna has been studied using epoxy glass FR4 substrate having parameters εr = 4.3, h = 1.6 mm, and tan δ = 0.025, respectively. In order to validate the simulation results, the proposed UWB antenna with dual-notch band characteristics is finally fabricated and measured. The fabricated antenna’s return-loss and far-field measurements show good agreement with the simulated results. The proposed antenna achieved the measured gain of 2.3 dBi, 4.9 dBi, and 5.2 dBi at 3.5 GHz, 6.1 GHz, and 9.25 GHz, respectively. Additionally, an in-depth comparative study is performed to analyze the performance of the proposed antenna with existing designs available in the literature. The results show that the proposed antenna is an excellent candidate for fifth-generation (5G) mobile base-stations, next-generation WiFi-6E indoor distributed antenna systems (IDAS), as well as C-band and X-band applications.

In this study, a dense Copernicus Sentinel-1 time series is analyzed to gain a better understanding of the influence of undergrowth vegetation, in particular of eagle fern (Pteridium aquilinum), on the C-band SAR signal in a temperate forest in the Free State of Thuringia, Germany. Even if signals from the ground below the canopy may not be expected at C-band, previous studies showed seasonal fluctuations of the backscatter for temperate forests without canopy closure, notably for evergreen coniferous stands. Many factors can be responsible for these observed fluctuations, but in this study, we analyze one possible factor: the presence of undergrowth vegetation, in particular, of fern. Especially, the Sentinel-1 backscatter signal is analyzed for different acquisition configurations regarding its temporal and its spatial stability at different growth stages. This time series study shows that a difference of backscattered signal of up to 0.7 dB exists between forest patches with a dense fern density in the understory and the ones with low undergrowth vegetation. This signal difference depends on the season and is remarkably strong comparing winter (no fern undergrowth) with summer (major fern undergrowth).

This study presents an approach for friction velocity and aerodynamic drag coefficient retrieval utilizing C-band VH SAR observations from Sentinel-1. The dataset contained 14 SAR images collected under six hurricane scenes co-analyzed with stepped frequency microwave radiometer (SFMR) measurements. The basis for creating this approach utilizes the results proposed earlier linking the parameters of the atmospheric boundary layer from GPS-dropsondes data to the ocean surface emissivity from SFMR measurements. The obtained dependencies of the ocean surface emissivity on surface friction velocity, aerodynamic drag coefficient, and surface wind speed are analyzed together with the collocated SAR data leading to the new GMF valid for the retrieval of friction velocities ranging from 0.55–1.56 m/s and drag coefficient values ranging from 0.00076–0.00232 for all sub swaths. Within the framework of the proposed approach, dependences of the normalized radar cross-section on the surface wind speed were also obtained and used for comparison with existing GMFs to show that the proposed approach is valid. A good consistency was obtained when comparing our results with H14E and MS1A. As an example the distributions of friction velocity, drag coefficient, and surface wind speed retrieved from the Hurricane Maria SAR image (23 September 2017) were considered.

Dense time series of stripmap RADARSAT-2 data acquired in the Multilook Fine mode were used for detecting and mapping the extent of selective logging operations in the tropical forest area in the northern part of the Republic of the Congo. Due to limited radiometric sensitivity to forest biomass variation at C-band, basic multitemporal change detection approach was supplemented by spatial texture analysis to separate disturbed forest from intact. The developed technique primarily uses multi-temporal aggregation of orthorectified synthetic aperture radar (SAR) imagery that are acquired before and after the logging operations. The actual change analysis is based on textural features of the log-ratio image calculated using two SAR temporal composites compiled of SAR scenes acquired before and after the logging operations. Multitemporal aggregation and filtering of SAR scenes decreased speckle and made the extracted textural features more prominent. The overall detection accuracy was around 80%, with some underestimation of the area of forest disturbance compared to reference based on optical data. The user’s accuracy for disturbed forest varied from 76.7% to 94.9% depending on the accuracy assessment approach. We conclude that change detection utilizing RADARSAT-2 time series represents a useful instrument to locate areas of selective logging in tropical forests.

This research proposes a compact quadri-cluster broadband circularly polarized (CP) sequentially-rotated metasurface-based (MTS) antenna array for the C-band frequency spectrum. One cluster of the quadri-cluster MTS-based antenna array consisted of 4 $\times $ 4 S-shaped periodically-arranged MTS elements. The sequentially-rotated feed network was utilized to realize circular polarization and improve the impedance bandwidth (IBW), 3-dB axial ratio bandwidth (ARBW) and 3-dB boresight gain bandwidth of the quadri-cluster MTS-based antenna array. Simulations were performed and results were compared with experiments. The measured IBW and ARBW were 84.74% (4.0–9.0 GHz) and 57.6% (4.2–7.6 GHz) at the center frequency of 5.9 GHz, rendering the proposed quadri-cluster MTS-based antenna array suitable for satellite communication applications. In addition, the quadri-cluster MTS-based antenna array achieved the measured 3-dB boresight gain bandwidth of 81.3% (3.9–8.7 GHz), the maximum gain of 10.04 dBic at 5.6 GHz, and low radar cross-section. Specifically, the novelty of this research lies in the use of the sequentially-rotated feed network with the S-shaped MTS elements to effectively enhance ARBW of the quadri-cluster MTS-based antenna array for the C-band frequency spectrum.

This paper explores a new concept for the design of high scanning-range phased array antennas: the Interleaved Parasitic Arrays Antenna or IPAA. In this concept, we use periodic parasitic elements and the generator impedance to control the Active Voltage Standing Wave Ratio (AVSWR) over a wide scanning range. This new array architecture comes with a design methodology enabling a smooth step-by-step design process aiming at reducing the need for full-wave calculations. First, a numerical dual-polarization design is presented in detail to illustrate the methodology and to give the design keys to the reader. Then, a prototype working in the 5G C-band between 3.4 and 3.8 GHz (11% bandwidth) was designed using this methodology and measured for a 36-element array. It is meant to demonstrate and validate the mutual coupling management done by the interleaved parasitic arrays and the design process accuracy. Good correspondence between measurements and simulation was found and the proposed unit cell with its corresponding tile can be integrated in a larger phased array with active modules to perform beam steering over an important scanning range without deteriorating the AVSWR. The proposed unit cell is designed for a high-scanning range going from $\theta =0^{\circ }$ to $\theta = 70^{\circ }$ for every $\varphi $ -directions and shows an active reflection coefficient for an infinite array below −13.6dB.

This research proposed an S-shaped metasurface (MTS)-based wideband circularly polarized (CP) patch antenna for C-band uplink frequency spectrum. The proposed MTS-based CP patch antenna was of low profile and fabricated on three substrate layers: upper, middle, and lower. The upper substrate contained $4\times 4$ periodic S-shaped MTS elements, the middle substrate functioned as ground plane with a rectangular-shaped slot at the center, and the lower substrate contained a coplanar waveguide with microstrip and ground. The S-shaped MTS elements converted linearly polarized (LP) into CP wave. Simulations were performed, and an antenna prototype was fabricated and experiments carried out. The measured impedance bandwidth and axial ratio bandwidth (ARBW) at the center frequency of 5.9 GHz were 43.22% (4.05 – 6.6 GHz) and 22% (5.3 – 6.6 GHz), respectively, rendering the proposed antenna suitable for satellite communication applications. The proposed antenna achieved the maximum gain of 6.16 dBic at 5.6 GHz. The novelty of this research lies in the use of S-shaped MTS elements to efficiently convert LP into CP wave and achieve wider ARBW for the C-band uplink spectrum.

Land cover mapping is essential to monitoring the environment and understanding the effects of human activities on it. The automatic approaches to land cover mapping (i.e., image segmentation) mostly used traditional machine learning that requires heuristic feature design. On natural images, deep learning has outperformed traditional machine learning approaches for image segmentation. On remote sensing images, recent studies demonstrate successful applications of specific deep learning models to small-scale land cover mapping tasks (e.g., to classify wetland complexes). However, it is not readily clear which of the existing models are the best candidates for which remote sensing task. In this study, we answer that question for mapping the fundamental land cover classes using satellite radar data. We took Sentinel-1 C-band SAR images available at no cost to users as representative data. CORINE land cover map was used as a reference, and the models were trained to distinguish between the 5 major CORINE classes. We selected seven among the state-of-the-art semantic segmentation models so that they cover a diverse set of approaches: U-Net, DeepLabV3+, PSPNet, BiSeNet, SegNet, FC-DenseNet, and FRRN-B. The models were pre-trained on the ImageNet dataset and further fine-tuned in this study. All the models demonstrated solid performance with overall accuracy between 87.9% and 93.1%, and with good to a very good agreement (kappa statistic between 0.75 and 0.86). The two best models were FC-DenseNet and SegNet, with the latter having a much smaller inference time. Overall, our results indicate that the semantic segmentation models are suitable for efficient wide-area mapping using satellite SAR imagery and also provide baseline accuracy against which the newly proposed models should be evaluated.

Data from TanDEM-X in single-pass and bistatic interferometric mode together with the interferometric water cloud model (IWCM) can provide estimates of forest height and stem volume (or the related above-ground biomass) of boreal forests with high accuracy. We summarize results from two boreal test sites using two approaches, i.e., 1) based on model calibration using reference insitu stands, and 2) based on minimization of a cost function. Both approaches are based on inversion of IWCM, which models the complex coherence and backscattering coefficient of a homogeneous forest layer, which includes gaps where free-space wave propagation is assumed. A digital terrain model of the ground is also needed. IWCM is used to estimate forest height or stem volume, since the two variables are assumed to be related through an allometric equation. A relationship between the fractional area of gaps, the area-fill, and stem volume is also required to enable model inversion. The accuracy of the stem volume estimate in the two sites varies between 16% and 21% for height of ambiguity

Recently different capacity boosting technologies, including 3D beamforming and expanding operating bandwidth have been investigated and included in the enhanced fourth generation (4G) and fifth-generation standards. For mobile operators to enhance their network performance, applying these advanced technologies is vital. To achieve that, planning and optimization work need to consider the spatiotemporal distribution of users. Although the capacity impact of advanced antenna technologies is investigated well, deployment options to exploit their benefits in a cost-effective manner considering a realistic network environment are seldom reported. This work presents a data driven and multi-objective based optimal vertical beams placement for an enhanced 4G mobile network with the newly introduced C-band. The method is utilized for an area located in Addis Ababa, Ethiopia, taking into account the existing 4G mobile network as a reference configuration. Users are distributed based on the data collected by ethio-telecom network management system. Findings indicate that optimal vertical beams placement achieved for gradual deployment with consideration cell edge and aggregate throughput performances while reducing network cost. While being cost-effective, up to 69.2% and 73.8% cell edge performance gain is achieved at 20 and 30 pareto points relative to an existing macro mobile network.

We demonstrate a C-band optical transmitter with an integrated widely-tunable III-V-on-silicon laser on the imec iSiPP50G platform using micro-transfer printing. Back-to-back operation at 40 Gbit/s non-return-to-zero On-Off keying over the C-band is presented.

Ultra-wideband antenna with band notch for rejecting bands. Rectangular slots are introduced on an arborescent patch to get UWB, coverage from 3.1–10.6 GHz. The antenna structure is fancied on FR4 the substrate with a size of 24 mm×24 mm×1.6 mm, a band notch located at 4.7 GHz is generated by adding the rectangular slot on the patch this microstrip antenna is simulated by computer simulation technology, the simulated and manufactured results show the antenna for wireless communication,to reduce the problem of interference in bands in communication systems by using the current distribution techniques, large bandwidths are reduced and unwanted bands are rejected by inserting notch such as rectangular slit and side slot on the patch. The presented antenna, use current redistribution technology, for the antenna designed by adding a rectangular aperture on a rectangular patch to change the current path to a zero value. Despite the fact that these antennas have strong band-notch characteristics and can match the criteria of UWB communication applications.

In this study, we assess the potential of X-band Interferometric Synthetic Aperture Radar imagery for automated classification of sea ice over the Baltic Sea. A bistatic SAR scene acquired by the TanDEM-X mission over the Bothnian Bay in March of 2012 was used in the analysis. Backscatter intensity, interferometric coherence magnitude, and interferometric phase have been used as informative features in several classification experiments. Various combinations of classification features were evaluated using Maximum likelihood (ML), Random Forests (RF) and Support Vector Machine (SVM) classifiers to achieve the best possible discrimination between open water and several sea ice types (undeformed ice, ridged ice, moderately deformed ice, brash ice, thick level ice, and new ice). Adding interferometric phase and coherence-magnitude to backscatter-intensity resulted in improved overall classification performance compared to using only backscatter-intensity. The RF algorithm appeared to be slightly superior to SVM and ML due to higher overall accuracies, however, at the expense of somewhat longer processing time. The best overall accuracy (OA) for three methodologies were achieved using combination of all tested features were 71.56, 72.93, and 72.91% for ML, RF and SVM classifiers, respectively. Compared to OAs of 62.28, 66.51, and 63.05% using only backscatter intensity, this indicates strong benefit of SAR interferometry in discriminating different types of sea ice. In contrast to several earlier studies, we were particularly able to successfully discriminate open water and new ice classes.

In this study, we analyse Sentinel-1 time series in order to characterise the observed seasonality of different land -cover classes in East-Thuringia, Germany and identify multi-temporal metrics for their classification. We consider different polarisations and different pass directions in order to assess their influence onf the multi-temporal backscatter profile. The observed seasonality is discussed together with meteorological information (precipitation & air temperature). The novelty of this approach is the determination of phenological parameters, like xxx, based on a tool that has been originally developed for optical imagery. Furthermore, several additional multi-temporal metrics are determined for the different classes, in order to investigate their separability for potential multi-temporal classification schemes. The results of the study show a seasonality for vegetation classes, which differs depending on the considered class: whereas pastures and broad-leaved forests show a decrease of the backscatter in VH polarisation during summer, an increase of the backscatter in VH polarisation is observed for coniferous forest in summer. Furthermore, a dependence of the backscatter of the pass direction (ascending /descending) is observed particularly for the urban land cover classes, whereas no difference is observed for other land-cover classes. Multi-temporal metrics indicate a good separability of principal land-cover classes, but further investigation and use of seasonal parameters is needed for a distinct separation of specific sub-classes. Theis analysis of the multi-temporal signature of Sentinel-1 backscatter data is a preliminary requisite for further physical modelling, i.e. quantify the respective impact of all influence factors on the Sentinel-1 backscatter signal using e.g. radiative transfer models.

In Winter 2017, the University of Massachusetts Amherst's Imaging Wind and Rain Airborne Profiler (IWRAP) was flown on a National Oceanic and Atmospheric Administration (NOAA) WP-3D Hurricane Hunter aircraft under the direction of scientists from Center for Satellite Applications and Research (STAR) at NOAA/National Environmental Satellite, Data, and Information Service (NESDIS) over the North Atlantic ocean out of Shannon, Ireland. IWRAP is a dual-frequency, conically scanning, profiling Doppler radar initially developed by Microwave Remote Sensing Laboratory (MIRSL) at the University of Massachusetts Amherst that is routinely installed on the NOAA WP-3D research aircraft. The flight on February 6, 2017, targeted a region of high winds (greater than 30 m/s) that was also observed by the Sentinel-1B satellite's synthetic aperture radar. Sentinel-1B was configured to observe in extended wide swath mode in both VV- and VH-polarizations, whereas the IWRAP C-band radar was configured to measure all of VV-, VH-, and HH-polarizations. IWRAP and Sentinel-1B VV and VH normalized radar cross section (NRCS) at the same Earthincidence angle along the flight path match reasonably well during the entire flight, but some additional trends between aircraft and satellite can be observed. IWRAP VV-polarized NRCS generally match the CMOD5.h geophysical model function (GMF), suggesting errors in the Sentinel-1B processing chain.

In this paper, we present a modified UWB antenna with hexagonal slotted ground plane inspired with a double combined symmetric T-shaped slots and dual rotated L-shaped strip for dual band notched characteristics. Initially, the operating frequency range is from 3GHz to 12 GHz. To eliminate the unwanted C-band (3.625-4.2GHz) and the entire uplink and downlink of X-band satellite communication systems (7.25 -8.39 GHz) frequency bands, we are investigating the conventional UWB patch antenna and loaded it with a mentioned strips and slots respectively. The performances of the antenna are optimized both by CST Microwave Studio and Ansoft HFSS. To further analyze the parametric effects of the slots and strips, the surface current distribution is presented and discussed. The antenna gain versus frequency gives an acceptable value except the notched band regions, these values are reduced from its normal to be a negative in the notched bands (3.625-4.2GHz) and (7.25 to 8.39 GHz).

Cerebellar Ataxia (CA) is a neurological disease with the symptom of poor coordination of movement and balance disorders. In clinical medicine, the heel-knee-shin test and the rapid alternating movements test are important basis for assessing CA. Based on the above tests, this paper presents a non-contact method and investigates the feasibility of this method for detecting CA. This body sensor networks uses wireless devices operating in the C-band frequency range to capture data of both types of tests without intrusiveness. The obtained data of tests contains massive useful information about human health which is really significant to subjects. But the information can be so subtle that people ignore the value hidden in it. So utility pattern mining (UPM) is used for the purpose of mining subjects’ activity pattern. We find that the subjects’ activity pattern differs greatly in amplitude information. We extracted the amplitude information that is helpful for analyzing the test’ results to determine whether the test is positive or negative. Then we use different kind of algorithms to classify the data samples. Among them, support vector machine (SVM) has the best classification effect on both tests. In the heel-knee-shin test, the coincidence rate ( $\pi$ ) is 98.7%, the sensitivity (Se) is 98.9% and the specificity (Sp) is 98.5%. In the rapid alternating movements test, the $\pi $ is 99.4%, Se is 99.8% and Sp is 99%. The experimental results show that this technique has the potential to open up new clinical opportunities for contactless and accurate CA monitoring in a patient-friendly and flexible environment.

In this paper, we propose and experimentally demonstrate a receiver-side electronic dispersion compensation (EDC) algorithm for direct-detection 56 Gbit/s on-off keying signal in C-band over 20 km dispersion-uncompensated standard single-mode fiber transmission. The proposed receiver-side EDC algorithm includes the feed-forward equalizer, post noise-whitening filter and modified iterative detection algorithm, which is originally used in spectrally efficient frequency division multiplexing systems for inter-carrier interference cancellation. Only with the aid of the proposed EDC algorithm for the compensation of power fading effect caused by bandwidth limit and chromatic dispersion, bit-error ratio below the 7% hard-decision forward error correction limit is achieved. This scheme can keep the system cost-effective and flexible, showing potentials for optical interconnects.

This article describes the first step toward the development of the geophysical model function (GMF) for the retrieval of wind speed and wind stress in hurricanes, based on developing a relation between the cross-polarized satellite SAR data from Sentinel-1 and winds/stress observed from collocated NOAA GPS-dropsondes data. Field measurements and remote sensing data for tropical cyclones in the Atlantic Ocean were analyzed. Using the data measured by GPS-dropsondes, average wind velocity profiles were obtained, while the parameters of the wind boundary layer (drag coefficient and friction velocity) were restored from the “wake” part of the velocity profiles using the self-similarity property. The self-similarity of the velocity profile “defect” in the boundary layer, known from the fluid dynamics, was used to retrieve the parameters of the atmospheric boundary layer (the surface wind velocity, drag coefficient, and friction velocity) from the dropsonde wind velocity profiles in ten major hurricanes. Based on the processing of the measurements in the hurricanes Irma 2017/09/07 and Maria 2017/09/21 and 2017/09/23 at a time close to the time of acquisition of the Sentinel-1 images, the dependencies of the cross-polarized normalized radar cross section on the wind speed and wind friction velocity were obtained and used for constructing the GMFs.

Development of satellite and radar applications has been continuously studied to reach the demand in the recent communication technology. In this study, a new oval-square-shaped split-ring resonator with left-handed metamaterial properties was developed for C-band and X-band applications. The proposed metamaterial was fabricated on 9 × 9 × 0.508 mm3 size of Rogers RO4003C substrate. The proposed metamaterial structure was designed and simulated using Computer Simulation Technique (CST) Microwave Studio with the frequency ranging between 0 to 12 GHz. The simulated result of the proposed design indicated dual resonance frequency at 5.52 GHz (C-band) and 8.81 GHz (X-band). Meanwhile, the experimental result of the proposed design demonstrated dual resonance frequency at 5.53 GHz (C-band) and 8.31 GHz (X-band). Therefore, with a slight difference in the dual resonance frequency, the simulated result corresponded to the experimental result. Additionally, the proposed design exhibited the ideal properties of electromagnetic which is left-handed metamaterial (LHM) behavior. Hence, the metamaterial structure is highly recommended for satellite and radar applications.

In this paper we present the simulative analysis of a 200 Gbps per wavelength (λ) 8-level pulse amplitude modulation (PAM-8) downstream communication over up to 20 km single mode fiber (SMF) in C-band based on direct detection (DD) achieving at least a 29 dB link power budget in a PON environment. We use chromatic dispersion digital pre-compensation (CD-DPC) and a dual-arm in-phase and quadrature Mach–Zehnder modulator (IQ-MZM) at the optical line termination (OLT) side, while preserving DD in the optical network unit (ONU). Three receiver digital-signal-processing (DSP) options are analyzed and compared: square-root-like technique (SQRT) in combination with a feed forward equalizer (FFE) and a decision feedback equalizer (DFE), the Volterra nonlinear equalizer (VNLE), and the SQRT in combination with the VNLE. The SQRT can be applied in combination with the VNLE to decrease the receiver DSP complexity while maintaining the required system performance. We show that PAM-8 with CD-DPC and the SQRT in combination with the VNLE is a feasible solution for 200 Gbps per λ downstream C-band transmission for PON.

This work presents an experimental analysis and comparison of the performance of quasi-randomly distributed reflectors inscribed into a single-mode fiber as a sensing mirror both in C- and L-band. Single-wavelength emission has been obtained in either band when using these artificially controlled backscattering fiber reflectors in a ring-cavity fiber laser. Single-longitudinal mode operation with an optical signal to noise ratio (OSNR) of 47 dB and an output power instability as low as 0.04 dB have been measured when employing a C-band optical amplifier. When replaced by an L-band optical amplifier, a single-longitudinal mode behavior has also been obtained, showing an OSNR of 44 dB and an output power instability of 0.09 dB. Regarding their performance as fiber-laser sensing systems, very similar temperature and strain sensitivities have been obtained in both bands, comparable to fiber Bragg grating sensors in the case of temperature and one order of magnitude higher in the case of strain variations. This work was supported in part by the MCIN/AEI/10.13039/501100011033 and FEDER A way to make Europe under Grant PID2019-107270RB, in part by the Ministerio de Educación, Cultura y Deporte of Spain under Ph.D. Grant FPU2018/02797, and in part by MCIN/AEI/10.13039/501100011033 and the European Union Next generation EU/PTR under Grant PDC2021-121172.

Frekans seçici yüzeyler (FSY), belirlenen frekans aralığında yüzeye gelen elektromanyetik dalgaların iletim, yansıma veya soğurma özelliği göstermesini sağlayan periyodik yapılardır. Bu çalışmada birden fazla frekans bandını kapsayacak şekilde (C-bandı (4-8 GHz) ve X bandı (8-12 GHz)), ultra geniş bant aralığına sahip, halka ve kesikli artı şekillerinin birleştirilmesiyle elde edilen yeni UGB FSY ile radar kesit alanının (RKA) azaltımı amaçlanmıştır. Çalışmanın ilk kısımlarında halka ve kesikli artı şekilli yapılar tek tek analiz edilmiştir. Analiz sonucunda en verimli olan iki yapı birleştirilerek elde edilen yeni FSY ile -10 dB kazanç değerinde bant genişliği arttırılmıştır. Önerilen yapı üzerinde temel parametreleri değiştirerek, ultra geniş bantlı (UGB) radar sistemlerinde kullanılabilecek iyi zayıflama düzeyine sahip, dalganın geliş açısından bağımsız ve bant durduran filtre karakteristiğine sahip yapı elde edilmiştir. Frequency selective surfaces (FSS) are periodic structures that allow electromagnetic waves arriving on the surface to show transmission, reflection or absorption properties in the determined frequency range. In this study, radar cross section with the new UGB FSY was obtained by combining ring and dashed cross shapes with ultra-wide band gap, covering more than one frequency band (C-band (4-8 GHz) and X-band (8-12 GHz)). In the first part of the study, the ring and dashed crosshairs were analyzed one by one. As a result of the analysis, the bandwidth has been increased by -10 dB gain with the new FSY obtained by combining the two most efficient structures. FSY designs with a good attenuation level that can be used in ultra-wideband (UGB) radar systems have been carried out. Simulation and analysis of the design were carried out with the CST Studio Suite 3D electromagnetic simulation program.

One promising and competitive solution to keep up with the rapid growth in data traffic while at the same time addressing increasing network cost, is the efficient reuse of legacy optical fiber infrastructure. This is highly desirable as deployed single mode fibers represent a valuable asset in the network while new installations would require high additional investments. Multiband (MB) or ultra-wideband (UWB) systems, combined with high symbol rates and higher-order modulation formats, are promising solutions to capitalize the already existing fiber plants. In this contribution, we experimentally demonstrate S-C-L-band reception with 64 GBd dual-polarization (DP) 64-ary and 32-ary quadrature-amplitude modulation (QAM) while using C band components off the shelf (COTS) such as DP-IQ modulators and coherent receivers. To achieve such broadband operation with components that are not optimized for an out of band use, mitigation of the associated penalties is decisive. To this end, we apply an end-to-end electro-optical Volterra based coherent system identification followed by nonlinear digital predistortion of the transmitter. We achieve 150-nm operation bandwidth of the transmission system by performing only a single identification and predistortion at a reference wavelength of 1500 nm.

In this paper, we illustrate the RF design and measurements of a C-band prototype structure for an Ultra High Dose Rate medical linac. (1) Background: FLASH Radiotherapy (RT) is a revolutionary new technique for cancer cure. It releases ultra-high radiation dose rates (above 100 Gy/s) in microsecond short pulses. In order to obtain a high dose in a very short time, accelerators with high-intensity currents (the order of 100 mA peak currents) have to be developed. In this contest, Sapienza University, in collaboration with SIT-Sordina IORT Technology spa, is developing a new C-band linac to achieve the FLASH regime. (2) Methods: We performed the RF electromagnetic design of the prototype of the C band linac using CST STUDIO Suite Code and the RF low power RF test at Sapienza University of Rome. The measurements of the field in the cavity have been done with the bead-pull technique. (3) Results: This device is a nine-cell structure operating on the π/2 mode at 5.712 GHz (C-band). We report and discuss the test measurement results on a full-scale copper prototype, showing good agreement with CST RF simulations. A tuning procedure has been implemented in order to ensure proper operating frequency and to reach a field profile flatness of the order of a few percent. (4) Conclusions: The prototype of a C-band linac for FLASH applications was successfully tested with low RF power at Sapienza University. The fabrication and ad hoc tuning procedures have been optimized and discussed in the paper.

Irrigation monitoring is important for the optimization of water use. Soil moisture (SSM) is a key variable for irrigation management. Furthermore, early detection of water stress can contribute to optimal irrigation water use. C-band radar data have shown great potential for monitoring soil and vegetation hydric conditions. In this context, the objective of this thesis is to evaluate the potential of C-band radar data in the monitoring of the water functioning of irrigated crops. The specific objectives are: (1) the development and evaluation of a new approach for SSM retrieval using radar data only; (2) the development of an approach for the estimation of irrigation timing and amounts at the plot scale basing on the new SSM products; (3) the investigation of the C-band radar response potentialities for the monitoring of the canopy physiological functioning and, in fine, the detection of water stress. First, the time series of Sentinel-1 data, including the backscattering coefficient (sigma^0), the polarization ratio (PR) and the interferometric coherence (rho) are analyzed based on field data collected over irrigated winter wheat fields in Morocco. The results show that rho and PR are highly related to vegetation development while sigma^0 was found to be sensitive to SSM variations during the early growth stages of wheat. In addition, drastic changes in the geometry of the canopy associated to the heading stage had a strong impact on sigma^0. The Water Cloud model (WCM) is then calibrated and validated over the study site. The results show that the model is able to reproduce the seasonal cycle of Sentinel-1. Thanks to a multi-layer configuration of the physical backscattering model Karam, the second cycle is attributed to the volume scattering from the upper layer composed of wet heads. Secondly, a new approach for SSM estimate based on the inversion of WCM is developed using only Sentinel-1 data. For this purpose, the aboveground biomass (AGB) and the vegetation water content (VWC) are estimated from rho and PR (which corresponds to four methods). These relationships are then used as vegetation descriptor in the WCM. The best SSM inversion results are obtained using the relationship between rho_VV and AGB (R = 0.82 and RMSE = 0.05 m3/m3). The SSM products derived using the method rho_VV-AGB are assimilated into the FAO-56 model using a particle filter technique based on a set of irrigation scenarios for irrigation timing and amounts estimation. First, synthetic experiments are designed in order to assess the impact of some parameters of the approach. In a second step, the method is evaluated using in situ SSM measurements with different revisit times (3, 6 and 12 days). Finally, the SSM products derived from the rho_VV-AGB approach are assimilated. Using in situ data, accurate results are obtained. With an observation every 6 days, the seasonal amounts are retrieved with R > 0.98 and RMSE < 32 mm. Similarly, over the flood-irrigated fields, more than 70% of the events are correctly detected. Using the SSM products derived from Sentinel-1, the statistics are still acceptable. For the drip-irrigated fields, the 15-day cumulative amounts are estimated with R = 0.64 and RMSE = 28.7 mm; metrics close to those obtained using in situ data (R = 0.74 and RMSE = 24.8 mm). Finally, the last part is devoted to the preliminary analysis of in situ radar acquisition by the C-band antennas installed on a wheat field in Morocco. The analysis of the fully polarimetric acquisitions (sigma^0 and rho) with a time step of 15 min reveals the existence of a diurnal cycle of rho whose amplitude evolves with the development of the canopy. The drop in rho at dawn is concomitant with the increase in evapotranspiration. In contrast, the lowest coherence values at the end of the afternoon are rather related to wind peaks.; Le suivi de l'irrigation est un enjeu important pour l'optimisation de l’irrigation. L'humidité superficielle (SSM) est une variable clé pour la gestion de l'irrigation. De plus, la détection précoce du stress hydrique peut contribuer à une utilisation optimale de l'eau agricole. Les données radar en bande C ont montré un grand potentiel pour le suivi des conditions hydriques du sol et de la végétation. Dans ce contexte, cette thèse a pour objectif général d’évaluer les potentialités des données radar bande C pour suivre le fonctionnement hydrique des céréales irriguées. Nos objectifs spécifiques sont : (1) développer une nouvelle approche pour l'inversion de la SSM en utilisant uniquement les données radar ; (2) proposer une méthodologie pour l’estimation des quantités et des dates d’irrigation à l'échelle de la parcelle sur la base de ces nouveaux produits de SSM ; (3) étudier les potentialités de la réponse radar bande C pour le suivi du fonctionnement physiologique et, in fine, la détection du stress hydrique. En préliminaire à l’inversion, les séries temporelles de données Sentinel-1, notamment le coefficient de rétrodiffusion (σ^0), le rapport de polarisation (PR) et la cohérence interférométrique (ρ) sont interprétées à l'aide de données expérimentales collectées sur des parcelles de blé irriguées au Maroc. Les résultats montrent que ρ et PR sont fortement liés au développement de la végétation alors que la dynamique de σ^0 suit les variations de SSM pendant les premiers stades de croissance du blé. En outre, les changements drastiques de la géométrie du couvert associés à la phase d'épiaison ont un fort impact sur σ^0. Les résultats montrent que le modèle Water Cloud (WCM) est capable de reproduire le cycle saisonnier de Sentinel-1. Grâce à une configuration multicouche du modèle Karam, le 2ème cycle est attribué à la diffusion de volume au sein de la couche des épis. Dans un 2ème temps, une nouvelle approche basée sur l'inversion du WCM pour estimer la SSM a été proposée en utilisant uniquement les données radar Sentinel-1. Dans ce but, les descripteurs de la végétation : la biomasse aérienne (AGB) et le contenu en eau de la végétation ont été estimés à partir de ρ et PR. Les meilleurs résultats d’inversion de SSM sont obtenus en utilisant la relation entre ρ_VV et l'AGB (R = 0.82 et RMSE = 0.05 m3/m3). Les produits SSM sont assimilés dans la FAO-56 par une technique de filtrage particulaire pour estimer les dates et les quantités d’irrigation. Premièrement, des expériences jumelles sont conçues pour évaluer l'impact de certains paramètres de l'approche. La méthode est ensuite évaluée en utilisant des mesures in situ de SSM avec 3 temps de revisite différents (3, 6 et 12 jours). Enfin, les produits de SSM Sentinel-1 dérivés par l’approche ρ_VV-AGB sont utilisés. L'utilisation de données in situ permet d'obtenir de bons résultats. Avec une observation tous les 6 jours, les quantités saisonnières sont inversés avec R > 0.98 et RMSE < 32 mm. De même, sur les parcelles en irrigation gravitaire, plus de 70 % des événements sont correctement détectés. En utilisant les produits SSM Sentinel-1, les statistiques restent raisonnables. Concernant les parcelles en goutte-à-goutte, les cumuls sur 15 jours sont inversés avec un R = 0.64 et RMSE = 28.7 mm; des métriques assez proches de celles obtenues en utilisant les données in situ (R=0.74 et RMSE = 24.8 mm ). Enfin, la dernière partie est consacré à l’analyse préliminaire d’acquisition radar in situ par des antennes bande C installées sur une parcelle de blé au Maroc. L’analyse des acquisitions pleinement polarimétriques (σ^0 et ρ) avec un pas de temps de 15 mn révèlent l'existence d’un cycle diurne de ρ dont l’amplitude évolue avec le développement du couvert. La chute de ρ à l’aube est concomitante avec l’augmentation de l’évapotranspiration. Par contraste, les valeurs de ρ les plus faibles en fin d’après-midi seraient plutôt dues aux pics de vent.

This study tested the ability of Sentinel-1 C-band to separate forest from other common land use classes (i.e., urban, low vegetation and water) at two different sites. The first site is characterized by temperate forests and rough terrain while the second by tropical forest and near-flat terrain. We trained a support vector machine classifier using increasing feature sets starting from annual backscatter statistics (average, standard deviation) and adding long-term coherence (i.e., coherence estimate for two acquisitions with a large time difference), as well as short-term (six to twelve days) coherence statistics from annual time series. Classification accuracies using all feature sets was high (>92% overall accuracy). For temperate forests the overall accuracy improved by up to 5% when coherence features were added: long-term coherence reduced misclassification of forest as urban, whereas short-term coherence statistics reduced the misclassification of low vegetation as forest. Classification accuracy for tropical forests showed little differences across feature sets, as the annual backscatter statistics sufficed to separate forest from low vegetation, the other dominant land cover. Our results show the importance of coherence for forest classification over rough terrain, where forest omission error was reduced up to 11%.

Proceedings of: 2021 International Symposium on Antennas and Propagation (ISAP), 19-22 October, 2021, Taipei, Taiwan. Design and analysis of a wideband compact flexible antenna is presented in this paper. The bandwidth enhancement of conventional triangular quarter wave monopole antenna is achieved by utilizing the combination of a fractal structure along with open ended stub. Moreover, the flexibility analysis was studied to show the stability of presented work for conformal analysis. Furthermore, compact size, wideband, stable performance in flexibility condition makes the proposed work potential candidate for WLAN, Wi-Fi and C-band Applications. This project has received funding from Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant Agreement No 801538. Also, this work is partially supported by Antenna and Wireless Propagation Group (AWPG); https://sites.google.com/view/awpgrp.

The upcoming launch of the L-band Synthetic Aperture Radar (SAR) satellite mission Radar Observing System for Europe L-band SAR (ROSE-L) will enable multi-frequency SAR observations when combined with existing C-band satellite missions (e.g., Sentinel-1). Due to the different penetration depths of the SAR signals, multi-frequency SAR offers great potential for field-scale agricultural monitoring and the estimation of soil and plant parameters. The SARSense campaign, conducted between June and August 2019 at the Selhausen agricultural test site near Jülich, Germany, has yielded a comprehensive dataset that includes both air- and space-borne C- and L-band SAR data, extensive in-situ field measurements of soil and plant parameters as well as unmanned aerial systems (UAS)-based multispectral and thermal infrared measurements and cosmic neutron sensing observations. The study provides both, an insight into the strengths and limitations of the acquired dataset as well as an analysis of the different behaviour of C- and L-band backscattering on changing soil moisture and plant parameters for taproot crops and cereals.

The multitemporal acquisition of images from the Sentinel-1 satellites allows continuous monitoring of a forest. This study focuses on the use of multitemporal C-band synthetic aperture radar (SAR) data to assess the results for forest type (FTY), between coniferous and deciduous forest, and tree species (SPP) classification. We also investigated the temporal stability through the use of backscatter from multiple seasons and years of acquisition. SAR acquisitions were pre-processed, histogram-matched, smoothed, and temperature-corrected. The normalized average backscatter was extracted for interpreted plots and used to train Random Forest models. The classification results were then validated with field plots. A principal component analysis was tested to reduce the dimensionality of the explanatory variables, which generally improved the results. Overall, the FTY classifications were promising, with higher accuracies (OA of 0.94 and K = 0.86) than the SPP classification (OA of 0.66 and K = 0.54). The use of merely winter images (OA = 0.89) reached, on average, results that were almost as good as those using of images from the entire year. The use of images from a single winter season reached a similar result (OA = 0.87). We conclude that multiple Sentinel-1 images acquired in winter conditions are feasible to classify forest types in a hemi-boreal Swedish forest.

In this paper we present an experimental analysis of several modulation formats (pulse amplitude modulation (PAM-2), quaternary pulse amplitude modulation (PAM-4) and electrical duobinary (EDB)) for passive optical network (PON) applications at 25 Gbps bit rate in a C-band 10G-class directly modulated lasers (DML) and avalanche photodiode (APD) intensity modulation and direct detection (IM-DD) system over a single mode fiber (SMF) of up to 25 km, optimizing DML operations and demonstrating that PAM-2 is a promising choice. We also theoretically and experimentally analyzed the channel frequency response of DML and SMF affected by DML chirp and SMF chromatic dispersion.