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A compact low‐profile dual‐band dual‐polarized wearable patch antenna, capable of working in 2.4 and 5.8 GHz ISM band for either on‐body or off‐body applications with different radiation patterns in each working band, is presented in this paper. The fabricated antenna consists of four layers including modified ground and patch layers and two dielectric layers made of jean fabric, and it has a radius of 30 mm with overall height of 3.4 mm fed by a single probe. The proposed structure is designed in a way that is capable of radiating linearly polarized (LP) waves in lower working frequency and circularly polarized (CP) waves in its upper working band. The ground plane is modified to ensure the dual‐band radiation as well as miniaturization of the antenna. The patch of the antenna benefits from truncated corners and four circular stubs which are practically coupled with antenna's modified ground to provide desired axial ratio and dual polarization capability. With the help of computer‐based simulations, the antenna is placed on human body tissue and the calculated amount of SAR values in each band for 1 g tissue is 0.15 and 0.89 Wkg, respectively, which guarantee the safety of the human body in close proximity to the antenna. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Substituting thermodynamically favorable ethanol oxidation reaction (EOR) for oxygen evolution reaction (OER) engenders high‐efficiency hydrogen production and generates high value‐added products as well. However, the main obstacles have been the low activity and the absence of an explicit catalytic mechanism. Herein, a heterostructure composed of amorphous vanadium oxide and crystalline nickel nitride (VOx−Ni3N) is developed. The heterostructure immensely boosts the EOR process, achieving the current density of 50 mA cm−2 at the low potential of 1.38 V versus reversible hydrogen electrode (RHE), far surpassing the sluggish OER (1.65 V vs RHE). Electrochemical impedance spectroscopy indicates that the as‐fabricated heterostructure can promote the adsorption of OH− and the generation of the reactive species (O*). Theoretical calculations further outline the dual polarization of the Ni site at the interface, specifically the asymmetric charge redistribution (interfacial polarization) and in‐plane polarization. Consequently, the dual polarization modulates the d‐band center, which in turn regulates the adsorption/desorption strength of key reaction intermediates, thereby facilitating the entire EOR process. Moreover, a VOx−Ni3N‐based electrolyzer, coupling hydrogen evolution reaction (HER) and EOR, attains 50 mA cm−2 at a low cell voltage of ≈1.5 V. This work thus paves the way for creating dual polarization through interface engineering toward broad catalysis. [ABSTRACT FROM AUTHOR]

This paper introduces a novel high-speed Visible Light Communication (VLC) system capable of transmitting data rates of 120 Gbps. The system leverages the multiplexing capabilities of Dual Polarization (DP) and Orbital Angular Momentum (OAM) beams. It incorporates three Laser Diode (LD) sources operating at distinct wavelengths: red (700 nm), green (570 nm), and blue (450 nm). Each LD source generates four OAM beams operating at DP states, with each OAM beam carrying a data rate of 5 Gbps. The proposed system is designed for indoor VLC applications, considering line-of-sight (LoS) link configurations. The proposed system is evaluated for different detector surface areas, and transmission distance. The bit error rate (BER), and eye diagrams as evaluation metrics are used to characterize the performance of the system. The findings of different detection areas reveal that larger surfaces yield superior performance, with significant reductions in BER observed at the cost of collecting more ambient noise. Additionally, shorter transmission distances exhibit enhanced performance, underscoring the importance of propagation range in VLC systems. Through extensive performance analysis, our proposed DP-OAM-VLC model achieves an overall transmission capacity of 120 Gbps at a range of 1.1 m, with a BER below 10−3.

Phase noise is a crucial impairment in coherent optical communication. In this paper, a dual-polarization 16 quadrature amplitude modulation coherent optical orthogonal frequency division multiplexing (DP 16-QAM CO-OFDM) modulation system with a hybrid optical filter has been proposed for phase noise reduction. This hybrid filter is a combination of an optical designed filter and an optical Gaussian filter. Linewidth of the input laser has been varied to generate phase noise. The simulation results have been obtained in terms of bit error rate (BER). It has been seen that the use of a hybrid optical filter mitigates the adverse effect of phase noise. [ABSTRACT FROM AUTHOR]

A third-order dual-polarized elliptic wide passband Frequency Selective Surface (FSS) has been proposed in this article. The unit cell is comprised of Y-shaped fractal geometry integration on the tri-pole and evolved as the stub-loaded tri-pole (SLTP) structure on an ultra-thin FR-4 substrate (ϵr = 4.4). The novel back-to-back cascading approach of the aforesaid proposed design array with optimized air spacer enhances electromagnetic coupling, resulting in maximally flat and substantially wider third-order bandpass filtering capability. −3 dB passband filtering performance (8.3–20.1 GHz) and −1 dB transmission characteristics (8.9–19.8 GHz) encompass the X and Ku band spectral ranges. The elliptical transmission coefficient leads to a remarkable passband selectivity factor (SF = 0.91). Equivalent circuit models (ECM) have been mapped, and the prototype has been experimentally validated. Angular stability (θ ≤ 40°) for both TE and TM polarizations ensures the employability of the proposed FSS for the radome. [ABSTRACT FROM AUTHOR]

Abstract Substituting thermodynamically favorable ethanol oxidation reaction (EOR) for oxygen evolution reaction (OER) engenders high‐efficiency hydrogen production and generates high value‐added products as well. However, the main obstacles have been the low activity and the absence of an explicit catalytic mechanism. Herein, a heterostructure composed of amorphous vanadium oxide and crystalline nickel nitride (VOx−Ni3N) is developed. The heterostructure immensely boosts the EOR process, achieving the current density of 50 mA cm−2 at the low potential of 1.38 V versus reversible hydrogen electrode (RHE), far surpassing the sluggish OER (1.65 V vs RHE). Electrochemical impedance spectroscopy indicates that the as‐fabricated heterostructure can promote the adsorption of OH− and the generation of the reactive species (O*). Theoretical calculations further outline the dual polarization of the Ni site at the interface, specifically the asymmetric charge redistribution (interfacial polarization) and in‐plane polarization. Consequently, the dual polarization modulates the d‐band center, which in turn regulates the adsorption/desorption strength of key reaction intermediates, thereby facilitating the entire EOR process. Moreover, a VOx−Ni3N‐based electrolyzer, coupling hydrogen evolution reaction (HER) and EOR, attains 50 mA cm−2 at a low cell voltage of ≈1.5 V. This work thus paves the way for creating dual polarization through interface engineering toward broad catalysis.

Abstract The metasurface is a promising technology that can help next-generation wireless communication systems not only improve the signal-to-noise ratio (SNR), but also increase security and mitigate interference. Further, introducing dual polarization (DP) in a metasurface can enhance its capabilities with polarization diversity, polarization multiplexing, and polarization-switched modulation. In this paper, we study a DP-metasurface-assisted single-user wireless communication system and propose a novel scheme that can improve the spectral efficiency (SE) and bit-error-rate (BER) performance compared to those of conventional schemes by exploiting the orthogonal property of dual-polarized waves. We employ the DP metasurface to increase the SNR at the receiver and create a specific phase difference between the polarized signals by controlling the transmit precoder and the phases of the metasurface reflecting elements representing some modulated bits. At the receiver, we use the recovered phase information to realign the modulated symbols in both polarizations, which are then added coherently. The simulation results demonstrate that the proposed scheme achieves significantly higher SE and BER performance than those of some closely related works.

Fast radio bursts (FRBs) are extraordinary astrophysical phenomena characterized by short radio pulses that last only a few milliseconds, yet their power can surpass that of 500 million suns. To date, most detected FRBs originate from beyond our galaxy. However, if an FRB were to originate within the Milky Way, it could be detected using small antennas. In this paper, we propose a compact and ad-hoc antenna array designed for the efficient detection and localization of FRBs within the Milky Way. The antenna operates within the 1200–1800 MHz range and consists of three sub-arrays placed in an L-shape for source localization, occupying a total volume of 8 0 × 2 5 × 6 cm 3 . Each sub-array consists of 4 miniaturized, dual-polarized, half-space radiation antenna elements, forming a one-dimensional array that allows shaping the radiation pattern to match the form of the Milky Way without exhibiting grating lobes. A prototype was constructed and characterized to validate the design. The measured results exhibit good agreement with the simulations. In addition to having a custom elongated radiation pattern, the array has attractive merits, such as low reflections at the input ports, high radiation efficiency, and a distribution that inhibits the existence of phase ambiguities, thus facilitating source localization. [ABSTRACT FROM AUTHOR]

The metasurface is a promising technology that can help next-generation wireless communication systems not only improve the signal-to-noise ratio (SNR), but also increase security and mitigate interference. Further, introducing dual polarization (DP) in a metasurface can enhance its capabilities with polarization diversity, polarization multiplexing, and polarization-switched modulation. In this paper, we study a DP-metasurface-assisted single-user wireless communication system and propose a novel scheme that can improve the spectral efficiency (SE) and bit-error-rate (BER) performance compared to those of conventional schemes by exploiting the orthogonal property of dual-polarized waves. We employ the DP metasurface to increase the SNR at the receiver and create a specific phase difference between the polarized signals by controlling the transmit precoder and the phases of the metasurface reflecting elements representing some modulated bits. At the receiver, we use the recovered phase information to realign the modulated symbols in both polarizations, which are then added coherently. The simulation results demonstrate that the proposed scheme achieves significantly higher SE and BER performance than those of some closely related works. [ABSTRACT FROM AUTHOR]

Noise Equivalent Beta Naught is the different noise influence that beneficence to the radar signal. This type of noise is available in TerraSAR-X satellite images and expressed in forms of scaled polynomial described the noise power. On the other hand, Sigma naught or backscattering coefficient represents the average reflectivity of a horizontal material samples which used to reflect the nature of the land use and land cover in radar images. In this paper, radar satellite images in dual VV and HH polarization were used to study the influence of the noise on backscattering image classification. The result demonstrated that the visual interpretation of sigma naught which is result from the comparison between existence case and absence case (in the other word: with and without noise) of the noise illustrated that there is no different between them. In the other hand, for more details and more precise, an example of small images are used to show the values of obtained backscattering. The result demonstrated that the NEBN plays the main roles in decreasing the values of backscattering coefficient in TSX image. The influence of this noise had usually high in water body surface, because this surface is generally having small backscattering coefficients compared with land cover. [ABSTRACT FROM AUTHOR]

A novel aperture‐shared dual‐wideband 5G antenna with dual polarization in the sub‐6 GHz band and multi‐input multi‐output (MIMO) function in the 28‐GHz band is presented in this work. A dual‐polarized megnetoelectric dipole (ME‐dipole) with wide bandwidth is introduced in the sub‐6 GHz band. Based on the partial structure reuse method, four 2 × 2 substrate integrated waveguide (SIW) cavity‐backed patch arrays are integrated into the electric dipole structure of the ME‐dipole to construct a 28‐GHz 2 × 2 MIMO system. Two high‐order SIW cavity modes that cooperate with patch modes are used to enhance bandwidth in the 28‐GHz band. For demonstration, a prototype of the proposed antenna was fabricated and measured. The simulated results are in good agreement with the measured results, showing wide bandwidths of 39.6% and 10.85% in the sub‐6 GHz and the 28‐GHz bands, respectively. In addition, excellent measured in‐band and cross‐band isolations of over 44.4 dB and 45.2 dB are obtained, respectively. [ABSTRACT FROM AUTHOR]

To simplify the structure of a multi-frequency base station antenna, this paper presents a three-frequency dual-polarization base station antenna for the 2G/3G/4G/5G band. The antenna consists of two pairs of three-ring dipoles placed at ± 45° to produce a ± 45° dual-polarization characteristic. The three current paths, produced by outer, middle and inner rings, correspond to the three operating bands respectively. Balun feed of the loaded slot and stub optimizes the three-band impedance matching of the antenna. The measurement results show that the impedance bandwidths of the antenna in the three frequency bands reach 46.7% (1.69–2.72 GHz), 19.2% (3.3–4 GHz) and 8.7% (4.4–4.8 GHz). In the operating band, the gain of 3.6–4 GHz is maintained at 7 ± 2 dB, and the gain of the rest of the working band is maintained at 9 ± 0.5 dB as a whole. The cross-polarization ratio of the main axis of the antenna is greater than 26 dB. The antenna designed in this paper has the advantages of wide band, high gain and high polarization purity compared with the traditional multi-frequency base station antenna. These attributes make the proposed antenna a potential candidate for 5G commercial base stations. [ABSTRACT FROM AUTHOR]

Noise Equivalent Beta Naught is the different noise influence that beneficence to the radar signal. This type of noise is available in TerraSAR-X satellite images and expressed in forms of scaled polynomial described the noise power. On the other hand, Sigma naught or backscattering coefficient represents the average reflectivity of a horizontal material samples which used to reflect the nature of the land use and land cover in radar images. In this paper, radar satellite images in dual VV and HH polarization were used to study the influence of the noise on backscattering image classification. The result demonstrated that the visual interpretation of sigma naught which is result from the comparison between existence case and absence case (in the other word: with and without noise) of the noise illustrated that there is no different between them. In the other hand, for more details and more precise, an example of small images are used to show the values of obtained backscattering. The result demonstrated that the NEBN plays the main roles in decreasing the values of backscattering coefficient in TSX image. The influence of this noise had usually high in water body surface, because this surface is generally having small backscattering coefficients compared with land cover.

【Objective】 The effects of Vertical-Vertical (VV) polarization, Vertical-Horizontal (VH) polarization, and dual polarization on microwave remote sensing retrieval of surface soil moisture (0-10 cm) were investigated. And analyze different data sources (Landsat-8, L8; Sentinel-2, S2) Effect of the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI) on the accuracy of remote sensing estimation of surface soil moisture. 【Method】 Based on the single polarization of VV and VH and the dual polarization model, NDVI and NDWI calculated by S2 and L8 were used to estimate vegetation water content (VWC), eliminate the influence of vegetation on backscattering, and obtain the soil backscattering coefficient. Then the water cloud model was used to invert the surface soil moisture in Daxing District of Beijing. 【Result】 For VV polarization, the estimation accuracy of VV+S2NDWI was best (R2=0.763, RMSE=1.55%). For VH polarization, the estimation accuracy of VH+S2NDVI was best (R2=0.622, RMSE=1.66%); The dual polarization (DP) + S2NDVI had a highest accuracy in retrieving surface soil moisture (R2=0.895, RMSE=0.89%); Compared with the NDWI, the NDVI has a better effect on removing the influence of vegetation, and the NDVI can be used to characterize the VWC. 【Conclusion】 NDVI is more suitable for removing the influence of vegetation in water cloud model, and the dual polarization method has higher accuracy in retrieving surface soil moisture.

This study presents dual polarization spectral analysis over updraft environments in thunderstorms. The composition and interaction of particle in updrafts environments are analyzed using the expansion that the spectral polarimetric provides in radar variables. Updrafts are identified using dual Doppler analysis and polarimetric signatures such as $Z_{\text{dr}}$ columns. Spectral techniques are presented to estimate the spectrum in updraft and mixed-phase environments. A separation in the spectrum of melting ice and rain was observed in the analyzed updrafts. This separation in the spectrum allows us to study the polarimetric characteristics and interaction of melting ice and rain. Furthermore, scattering simulations were carried out to validate the spectral signatures attributed to melting ice. It was found that small ice particles mixed with rain can produced similar polarimetric characteristics as the one observed in the spectral analysis. Conceptual models based on the spectral observations are presented to illustrate the interaction of ice particles with a recirculation and a vigorous updraft.

This paper proposes dual-band dual linearly-polarized (LP)/circularly-polarized (CP) antennas using combined metasurface and patch for ultra high frequency (UHF) and 2.45-GHz RF identification (RFID) readers. A metasurface and two stacked patches are employed for the lower and upper bands, respectively. The metasurface and patches are incorporated with a common feeding structure which is composed of two orthogonal microstrip lines and a crossed slot to produce the dual-wideband dual-LP radiation. To reduce the back radiation and improve the gain, the antenna is backed by a metallic cavity. Taking advantage of its low-profile structure, the dual-LP antenna is further integrated with a dual-band branch-line coupler to realize dual-CP radiation. Both proposed antennas yield stable radiation performances across dual operating bands which completely cover the assigned RFID spectrum at the UHF ( $860-960$ MHz) and 2.45-GHz ( $2400-2500$ MHz) bands.

Effective ship detection in synthetic aperture radar (SAR) imagery is crucial for maritime safety and surveillance. Despite the advancements in deep learning for SAR ship detection, significant challenges remain, particularly in large scenes. These challenges are twofold: the detection of extremely small ships is often hindered by inadequate feature extraction, and the presence of inshore ships is obscured by pronounced land-based interference, both of which lead to reduced detection accuracy. To address these issues, we present a novel deep learning framework that integrates constant false alarm rate (CFAR) processing with dual-polarization data, termed the CFAR-guided dual-polarization fusion framework (CFAR-DP-FW). The integration is designed to enhance the detection sensitivity for small-scale maritime targets by utilizing dual-polarization's rich feature representation, and CFAR's strength in suppressing background noise, highlighting potential targets. The proposed CFAR-DP-FW consists of three core components: the CFAR dual-polarization detector provides initial target indication; the CFAR field generator constructs a probabilistic ship presence map, reducing reliance on CFAR's hard thresholds; and the CFAR guidance dual-polarization network incorporates a novel feature extractor and enhancement module, tailored to amplify relevant features, and suppress noise. This strategic fusion within our framework markedly improves the detection of small and inshore ships. Evaluated on the large-scale SAR ship detection dataset-v1.0, our framework demonstrates superior performance, surpassing 20 state-of-the-art models. It achieves a 3.28% increase in mean average precision for inshore ships over the next best-performing model, validating its efficacy in tackling the intricate challenges of large-scale SAR ship detection.

A novel‐shaped dual‐polarized low‐profile multiple‐input multiple‐output (MIMO) antenna with high isolation is proposed for 5G/WLAN application. An 8‐element MIMO antenna design comprises two unique planar radiators (chamfer, circular). Each radiator has dual feed and dual polarization characteristics. The prototype is fabricated with an FR‐4 dielectric substrate. A decoupling structure maintains desirable isolation for self‐isolated elements (≤ $\le $−12 dB) using substrate integrated waveguide stubs between inter‐ports and high isolation among the adjacent radiating elements (≤ $\le $−15 dB). The simulation was performed by using CST microwave studio. The simulated results of the proposed MIMO antenna are compared with the measurement results. Furthermore, ECC and DG are investigated. [ABSTRACT FROM AUTHOR]

In order to prevent and manage damage caused by localized torrential downpours, the quantitative observation of rainfall is crucial. Considering the spatial complexity and vertical variability of rainfall, it is important to obtain low-altitude, high-resolution radar observations to reduce uncertainty in radar rainfall estimates. In this paper, we present an electromagnetic wave rainfall gauge system (EWRG) that detects rainfall within the observation area and estimates the areal rainfall using electromagnetic waves. The EWRG system was developed based on a subminiature size antenna, a K-band dual-polarization transceiver, and advanced high-resolution, high-speed signal processing technology. The system design and signal processing techniques are described in detail. The EWRG has the advantage of overcoming the limitations of conventional cylindrical ground rain gauges, such as the contamination and spatial inaccuracy of rain gauges, which cause uncertainty in quantitative precipitation measurement. [ABSTRACT FROM AUTHOR]

This letter proposes a novel synthetic aperture radar (SAR) time series analysis method based on the scattering power decomposition algorithm with a reasonable ensemble average in both temporal and spatial domains. We reveal that the ensemble average is effective not only in the spatial domain but also in the temporal–spatial domains in the scattering power decomposition. That is, if we extend the ensemble average window in the temporal domain, the proposed method can accurately achieve volume scattering power with a higher spatial resolution than conventional approaches. The precise volume scattering power serves accurate forest monitoring. As an application, we performed forest disturbance detection in the Amazon rainforest using Sentinel-1 time series data. The proposed method detected the disturbances earlier, in less than 2 months, compared to other methods that take about 3 months. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An estimate of the processes of afforestation and forest restoration after fires is relevant for a significant territory of Russia, including due to the issue of carbon neutrality. In this paper we examine the possibilities of radar monitoring of the afforestation process based on the Cloude–Pottier decomposition of dual-polarization L-band data time series. Preliminary segmentation is performed based on the minimal radar backscatter values for the entire observation period. This makes it possible to separate into a separate class treeless areas and open forests, both those that existed before the beginning of the study and those that formed later. Next, polarimetric decomposition is performed by the Cloude–Pottier method to obtain parameters H (entropy) and α (scattering angle) and form time series from them. Research showed the fundamental possibility of monitoring forest dynamics on the H-α plane, where the points of the test plots form characteristic time tracks. A mature dense forest, the characteristics of which are assumed to be constant, was used as a reference for estimating the rate of change on the H-α plane. [ABSTRACT FROM AUTHOR]

Based on the detection data of an S-band dual polarization Doppler weather radar in Jining, Shandong province, and combined with sounding and surface meteorological observation data, the characteristics of dual polarization parameters and microphysical characteristics of supercells in a heavy rainfall in Shanxian, Shandong province on June 14, 2021 are analyzed. The results are shown as follows. The humidity of the whole layer of the environment is relatively high, CAPE is relatively strong, and the height of the 0 °C layer is relatively high, which is conducive to the generation of heavy precipitation. Vertical wind shear at moderate intensity is found at the heights of 0~6 km, which is conducive to the generation and maintenance of the supercell storm. The intensity of the supercell storm in Shanxian is 60~65 dBZ at the peak stage, the height of an intensity center is basically below the 0 °C level, and the core of mass is low. The height and width of the KDP column are much larger than that of the ZDR column. A strong and wide updraft brings small liquid particles with some degree of concentration to a higher height for extended time. On the left side of the lower storm level, there are always areas of large KDP values, with some of them more than 3°/km. The concentration of liquid particles is high, and the maximum precipitation rate is maintained at more than 3 mm per minute. On the right side of the lower layer of the storm, there are an inflow gap and a ZDR arc clearly, shown as relatively large liquid particles. There are abundant liquid - and ice-phase particles in the deep thickness above the height of the 0 °C layer in the environment. When abundant ice-phase particles drop below the height of the 0 °C layer, they melt by large amount. Under the "screening" effect of a strong shear in the lower layer, the junction area between the inflow and the downdraft on the right side of the storm is dominantly with large liquid particles with low concentration and rainfall intensity is low. The lower layer on the left side of the storm has high concentration of liquid particles, resulting in high-intensity precipitation. [ABSTRACT FROM AUTHOR]

A simple process for the design of broadband planar antennas is presented for base station applications. The process is based on a square patch above a ground plane. Only three geometric parameters are involved in the design of a dual-polarized broadband planar antenna, including the width (W s) of the square patch, a trimming angle (θ) of the square, and the height (H) of the patch above the ground plane. By adjusting the critical parameters θ and H , an impedance bandwidth of 50% for return loss (RL) >15 dB is achieved with an isolation of higher than 35 dB. The bandwidth of the broadband planar antenna is enhanced to 67% by etching four Γ slots on the square patch. The operating mechanisms of these broadband antennas are analyzed and verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, a dual-polarized broadband metasurface antenna is proposed. The antenna consists of a new Metasurface patch which is formed from different cross shapes to achieve wide bandwidth and expedite dual polarization features. The radiating metasurface patch is fed by a novel coplanar waveguide fed structure to facilitate achieving dual polarization. The proposed antenna has a wide bandwidth of 2.82 GHz over an operating frequency range between 3.36–6.2 GHz with 10 dBi maximum realized gain. The proposed antenna has been fabricated and the simulated results have been validated experimentally. It is believed that the proposed antenna is a good candidate for sub 6 GHz of 5G application. [ABSTRACT FROM AUTHOR]

Crop identification and acreage estimation are always challenges for passive remote sensing in cloudy environments, especially during the rainy season. Microwave remote sensing data, with its availability and advantages of cloud penetration, can offer a solution to this problem. In the present study, a dual-pole polarization Sentinel-1 (C-band) SAR dataset was used for the assessment of the paddy temporal growth stage in the Alathur block of Kerala, India. The acreage estimation of coconut, fallow, mixed trees, paddy, rubber, plantation, paddy-coconut, and plantation fallow classes were also carried out using ArcGIS software. The multi-temporal data from June 2021 to October 2021 is openly accessible from the European Space Agency (ESA) via the Sentinel-1. The image was preprocessed for radiometric corrections, speckle filtering, terrain correction, and co-registration, and was finally converted from a linear to a decibel (dB) domain using ESA (SNAP software). The crop discrimination of paddy and other classes was also classified by using the decision tree rule (DTR), K-nearest neighbors, minimum distance (MD), and random forest (RF) classifiers. The results revealed that during the early stage of the paddy crop, specular reflection occurred, which enabled a low backscatter signature of − 18.45 to − 10.9 dB in VH (vertical transmit and horizontal receive) and in VV (vertical transmit and vertical receive) polarization, and with each growth stage of the crop, the backscatter varied. However, there was no significant variation observed for coconut (− 15.02 dB) in VH (vertical transmit and horizontal receive) and (− 8.67 dB) in VV (vertical transmit and vertical receive) and for Rubber (− 14.57 dB) in VH (vertical transmit and horizontal receive) and (− 7.78 dB) in VV (vertical transmit and vertical receive) as compared to paddy field. The results obtained for paddy and other classes from different classifiers revealed that random forest (RF) and K-nearest neighbor classifications gave 95.0 percent and 94.0 percent accuracy for the classification of paddy, respectively, as compared to decision tree rule (DTR) and minimum distance classification. [ABSTRACT FROM AUTHOR]

The nonlinear frequency division multiplexing (NFDM) transmission scheme continues to attract high interests in optical communications due to its robustness against nonlinearity and dispersion. The use of Hermite Gaussian (HG) wave-carriers has been proposed and has been shown to out-perform conventional methods used by state-of-the-art single polarization NFDM systems due to their excellent time-bandwidth-product (TBP) efficiency. In this work, employing the Manakov model, we investigate and demonstrate, for the first time, a high-capacity dual polarization NFDM (DP-NFDM) transmission system based on HG wave-carriers, enhanced by a single parameter equalizer. We report here, a record high spectral efficiency of 12 bits/s/Hz for dual-polarization HG-based DP-NFDM systems.

Accurate measurement of angular positions on the sky requires a well-defined system of reference, something that in practice is realized by the International Celestial Reference Frame (ICRF) with observations of distant (typical redshift $\sim$1) Active Galactic Nuclei (AGN). At such great distances a subset of these objects exhibit as little as 10$-$50 $\mu$as/year observed parallax or proper motion, thus giving the frame excellent spatial and temporal stability. Until fairly recently the majority of AGN centered imaging was accomplished in the S (2.3 GHz) and X (8.4 GHz) radio frequency bands, however S-band observations for reasons such as sensitivity “plateauing”, increased source structure (jets), and radio frequency interference (RFI) have become less productive. Following spacecraft telemetry moves to higher frequencies and a desire to strengthen JPL's leadership in defining the next-generation of celestial reference frames has motivated the development of a “Quad-band” prototype receiver that operates in X, Ku, K, and Ka band in both right hand (RCP) and left hand (LCP) circular polarization. The goal of this receiver is to achieve less than a 20 % increase in noise over the Jansky Very Large Array (JVLA, NRAO) performance specification, which in such a wide bandwidth represents a revolutionary capability. To evaluate the various technical developments of the 8 GHz$-$40 GHz receiver the feedhorn optical beam was designed to interface to the US based Very Long Baseline Array (VLBA). The receiver's intermediate frequency (IF) spans 4 GHz$-$8 GHz, giving rise to up to eight 4 GHz IF channels for a fully populated instrument. This paper outlines the technical development of a 2$^{1}$/$_{2}$ octave wide (8 GHz$-$40 GHz) X-Ka band prototype receiver, fulfilling a need for super broadband technology within the VLBI network. An important additional benefit of the wideband receiver approach is its simplicity and low cost of operation.

This paper presents a low-profile wideband, dual-polarized patch antenna using differential-paired, multi-mode arms. By employing the arrow-shaped, differential-paired arms, three modes of them are excited simultaneously, leading to a broad bandwidth. The shorting pins are uniquely inserted at the wings of the arms to obtain stable radiation patterns. Then, two pairs of arms are structured like the dipoles and a dual-polarized antenna is designed. In addition, by employing coplanar coupling feeding structures, a good wideband impedance matching is also achieved without increasing the height. For demonstration, a wideband dual-polarized patch antenna is designed and measured. Benefitting from the advantages of the multi-mode patch and symmetrical structure as a dipole antenna, the proposed dual-polarized antenna operates between 2.10–3.95 GHz, possessing a 10-dB impedance bandwidth of 61%, a profile of 0.1λ0, an average gain of 7.31 dBi, and stable radiation patterns. [ABSTRACT FROM AUTHOR]

Because of its good beam coverage and beam scanning abilities, the Luneburg lens (LL) is a promising multibeam antenna for the fifth-generation (5G) wireless communications. However, the conventional LL has a spherical formfactor, exhibiting a large volume, large weight, and curvature surface, all of which limit the adoption of an LL in practice. To alleviate the problem, a flat LL is proposed, with transformation optics to convert the conventional spherical structure into a flat one. However, a high permittivity distribution is usually required in a transformed flat LL, causing of server reflections, which further degenerates the performance of the LL in terms of both gain and efficiency. In this article, a millimeter-wave dual-polarized flat Luneburg lens antenna (FLLA) is proposed following the transformation of optics, and implemented using multilayer PCBs, where a reflection cancellation method is introduced to optimize the multilayer structure to improve its gain and efficiency. The designed FLLA is exemplified in the Ka-band and fed using a dual-polarized patch antenna. The measured results show that the designed FLLA has an impedance bandwidth (|S11| ≤ −10 dB) of 27.5–32.6 GHz, a gain of 16.8–18.8 dBi over the operating band, and a beam scanning range up to ±25°/±24° with a gain loss of 1.72 dB/1.7 dB in either E- or H-plane, respectively. [ABSTRACT FROM AUTHOR]

In this article, a microwave (MW)/millimeter wave (MMW) aperture-sharing antenna is proposed. The antenna is constructed using two orthogonal columns of grounded vias from a 3.5 GHz slot-loaded half-mode substrate-integrated waveguide (HMSIW) antenna. These vias are reused to create two sets of 1 × 4 MMW substrate-integrated dielectric resonator antenna (SIDRA) arrays. With this proposed partial structure reuse strategy, the MW antenna and MMW arrays can be integrated in a shared-aperture manner, improving space utilization and enabling dual-polarized beam steering capability in the MMW band, which is highly desirable for multiple-input multipleoutput (MIMO) applications. The integrated antenna prototype was manufactured and measured for verification. The 3.5 GHz antenna has a relative bandwidth of 3.4% (3.44–3.56 GHz) with a peak antenna gain of 5.34 dBi, and the 28 GHz antenna arrays cover the frequency range of 26.5–29.8 GHz (11.8%) and attain a measured peak antenna gain of 11.0 dBi. Specifically, the 28 GHz antenna arrays can realize dual-polarization and ±45° beam steering capability. The dual-band antenna has a very compact structure, and it is applicable for 5G mobile communication terminals. [ABSTRACT FROM AUTHOR]

The use of SAR data for flood mapping is well established. However, the problem of the missed detection of rapidly evolving floods remains. Recently, the Italian Space Agency deployed the COSMO-SkyMed Second Generation (CSG) constellation, with an on-demand capability that makes it possible to reduce the number of missed floods. However, for on-demand SAR acquisitions, pre-flood images are generally not available, and change-detection methods, commonly adopted for flood mapping using SAR, cannot be applied. This study focused on the high-resolution CSG images of a flood that occurred in central Italy. An accurate analysis of the radar responses of the different targets included in the scenes observed by GSG was performed. Then, a methodology to detect floods using high-resolution single SAR images was developed. The methodology was based on image segmentation and fuzzy logic. Image segmentation allowed us to analyze homogeneous areas in the CSG images. Fuzzy logic was used to integrate the SAR data with ancillary information that was useful when change-detection methods could not be applied. A comparison with the maps produced by the Copernicus Emergency Service, using high-resolution optical images, demonstrated the reliability of the methodology. [ABSTRACT FROM AUTHOR]

This paper presents a novel design for and an experimental study of a dual-polarized quad-port MIMO antenna. The design achieves resonance at five distinct frequency bands with reduced mutual coupling. The design includes a single annular ring slot, four truncated rectangular corners, and a truncated aperture to improve resonance behavior. The design is then extended to a four-port MIMO antenna by including a ground-plane slit to enhance isolation between antenna elements at the center resonance band. The antenna achieves resonances at 5 distinct bands, ranging from 1.5 to 8.4 GHz, with significant mutual coupling reductions. The resonances of the quad-port pentaband MIMO antenna are achieved at 1.55 GHz (1.5–1.65 GHz), 2.5 GHz (2.4–2.7 GHz), 5.2 GHz (5–5.85), 7.3 GHz (7.1–7.4), and 8.15 GHz (7.9–8.4), with respective mutual coupling reductions of 27 dB, 37 dB, 21 dB, 29 dB, and 21 dB. Additionally, the 3 dB axial ratio bandwidth (ARBW) is observed at 6.5% (1.5–1.6 GHz) and 15% (2.4–2.7 GHz) in 2 distinct bands, and the envelope correlation coefficient and diversity gain are calculated within the specified band range. Experimental measurements of the prototype for the quad-port antenna are conducted, with excellent agreement found between the results and the simulations. [ABSTRACT FROM AUTHOR]

A differentially fed dual-polarization slotted antenna with an ultra-wide bandwidth and low cross polarization is presented in this paper. The antenna is composed of a radiation patch and a ground plane, both of which are printed on the top of the dielectric substrate. The ground is extended toward the radiation patch to form a slotted coplanar structure. In order to expand the bandwidth, a cross-shape symmetrical slotted structure is loaded into the radiation patch. Differential feed is adopted to realize 0°C/90°C linear polarizations and suppress the cross polarization. Simulation and measurement results show that the proposed antenna with dimensions of 0.53λC0 × 0.53λ0 × 0.0135λ0 (λ0 is the wavelength at 4 GHz) has a differential mode impedance bandwidth of 82.25% (2.27-5.56 GHz), a differential feed port isolation of higher than 28 dB, and a cross polarization level of less than -30 dB, which achieves the characteristics of ultra-wideband, high isolation, and low cross polarization level. [ABSTRACT FROM AUTHOR]

A broadside direction gain-enhanced low-cost dual-polarized microstrip patch antenna has been presented. The proposed antenna consists of a slot-loaded cross-shaped patch and shorting pins. The orthogonal polarized radiating elements works in TM05 and TM12, meanwhile slot-loaded excite TM01. The equivalent magnetic currents (EMCs) amplitude, frequency, and flow direction of the TM12 are controlled by shorting pins to form the broadside gain enhancement. The superposition of them can enhance the gain in the broadside direction. The proposed antenna is coaxial feed. The substrate is divided into two layers: air and FR4. A copper column is added to the air layer to greatly improve the polarized isolation of the antenna. The size of the proposed antenna is 2.29λ0×2.29λ0×0.069λ0 (λ0 is the wavelength of free space at the central frequency). The simulated maximum realized gain is 12.59 dB, and the realized gain is better than 11.53 dB in operating band. The measured maximum realized gain is 12.05 dB, and the realized gain is better than 10.04 dB. The dual-polarized microstrip patch antenna has the advantages of low cost and high gain, which can be used in the modern wireless communication system. [ABSTRACT FROM AUTHOR]

This paper describes the design of a W-band dual polarized slotted waveguide (WG) array antenna. The slotted WG array is arranged on an annular disk, and so the feeding technique for this annular slotted WG array is more complicated than a regular array such as rectangular array. Broad wall longitudinal offset slot WG and edge wall inclined slot WG are staggered in turn to form the dual polarized array. In order to reduce the spacing between two adjacent WGs, ridged WG is adopted for designing broad wall longitudinal offset slot array. For making the beam width equal in two orthogonal principal planes, parameters of the WGs are carefully selected to ensure that the spacing between longitudinal adjacent slots is equal to that between transverse adjacent slots. The feeding networks for the annular disk WG array are carefully designed in irregular shapes, which can split electromagnetic waves to each WG (of the array) in phase. Finally, the antenna is processed and tested. Simulated results and measured results are presented. Measured gains of the horizontal polarization (HP) and vertical polarization (VP) are 35 dBi and 31.5 dBi, respectively, and efficiencies of the HP and VP are 56% and 28%, respectively, estimated from the measured gains and the calculated directivities. [ABSTRACT FROM AUTHOR]

Dual polarization is achieved by putting a rectangular or circular patch in between two orthogonal gaps. At the beginning a single-polarized patch is considered. Then by using anequivalent circuit, the impedance matching property of the gap is being configured. After optimization of the length of the patch and width of the gap, a dual polarized antenna is being considered. Here in this article we projected a new technique to design dual polarized microstrip antenna for WLAN, WiMAX, wireless applications using circular patch. By combining all resonant modes we have finally achieved a wide operating bandwidth. Experimental result of the projected antenna shows the operating bandwidth of 21.56% (5.24–6.37 GHz) for (differential mode S-parameter) Sdd11 ≤ −10 dB with a high port isolation of 40 dB and a relative gain of 13.5 dBi is achieved. From the result analysis this antenna finds its applications for various WLAN and Wi-MAX frequency band. [ABSTRACT FROM AUTHOR]

As a key component of rainfall estimation, the understanding of raindrop size distribution (DSD) is a long-standing goal in meteorology and hydrology. Given that weather radar can observe the precipitation microphysics over large spatial and temporal scales, it has been broadly applied in DSD estimation. Traditional polynomial regression algorithms that correlate DSD parameters and radar signatures are still widely applied due to their simple structure and acceptable accuracy. This study proposes a new DSD retrieval model using dual-polarization radar observations based on long short-term memory (LSTM) network techniques. Three schemes able to retrieve the parameters of a normalized gamma DSD (LSTM- D 0 , LSTM- N w , and LSTM- μ) are proposed with different combinations of polarimetric radar measurement inputs. All LSTM estimators exhibit better performance than the polynomial regression method. The Nash-Sutcliffe efficiency coefficient for estimates of drop median diameter (D 0) and intercept parameter (N w) increases from 0.93 and 0.70 to 0.95 and 0.93 respectively at Chilbolton station. Poor estimates of the shape parameter (μ) using the polynomial regression estimator complicate real applications, whereas the remarkable improvement of LSTM model estimation facilitates practical applications. The temporal and spatial predictability is then estimated to investigate long-term estimator performance for various radars, or at least for all radar pixels of a single radar. The predictability, measured by the Nash coefficient, increases temporally by 0.08, 0.31, and 0.39 and spatially by 0.03, 0.19, and 0.23 for the parameters D 0 , log 10 N w , and μ respectively. This study contributes to improving quantitative precipitation estimates from radar polarimetry, enabling a better understanding of precipitation microphysics. • A new DSD retrieval model using dual-polarization radar observations based on LSTM network techniques was proposed. • The UK-wide study on 14 disdrometers revealed LSTM as an effective approach to enhance DSD parameter retrieval accuracy. • The temporal and spatial predictability for DSD parameters using LSTM are all better than that of the traditional methods. [ABSTRACT FROM AUTHOR]

Valley photonic crystal (VPC) waveguides possess strong immunity to backward scattering and robust transmission, originating from topologically protected edge states. Here, we propose a VPC/air/VPC sandwiched structure, and VPC possesses the common valley band gaps for TM and TE polarizations. By modifying the radii of the cylinders on both sides of the air channel, finite element method (FEM) simulations show the valley-locked waveguide modes with high flux are achieved, for both polarizations. Based on VPC/air/VPC sandwiched structure, we further design waveguide couplers and zigzag waveguide bends, and immunity to backward scattering and robust transmission are also verified. Our work finds a new method of designing photonic crystal waveguides, which support valley-like transport with enhanced flux and dual-polarization, making topological photonic devices easily to be integrated with conventional optical waveguides. • A VPC/air/VPC sandwiched structure, which possesses the common valley band gaps for both polarizations, is proposed. • Valley-locked waveguide modes for both polarizations with high flux are achieved. [ABSTRACT FROM AUTHOR]

In order to prevent and manage damage caused by localized torrential downpours, the quantitative observation of rainfall is crucial. Considering the spatial complexity and vertical variability of rainfall, it is important to obtain low-altitude, high-resolution radar observations to reduce uncertainty in radar rainfall estimates. In this paper, we present an electromagnetic wave rainfall gauge system (EWRG) that detects rainfall within the observation area and estimates the areal rainfall using electromagnetic waves. The EWRG system was developed based on a subminiature size antenna, a K-band dual-polarization transceiver, and advanced high-resolution, high-speed signal processing technology. The system design and signal processing techniques are described in detail. The EWRG has the advantage of overcoming the limitations of conventional cylindrical ground rain gauges, such as the contamination and spatial inaccuracy of rain gauges, which cause uncertainty in quantitative precipitation measurement.