Dual Polarization Characteristics Research Articles

Impact of Directly Assimilating Radar Reflectivity Using a Reflectivity Operator Based on a Double-Moment Microphysics Scheme on the Analysis and Forecast of Typhoon Lekima (1909)

In previous studies, radar reflectivity is often directly assimilated using reflectivity operators based on a single-moment (SM) microphysics scheme, though the forecast model uses a double-moment (DM) microphysics scheme. With the fixed number concentrations, only the mixing ratios of hydrometeors are directly updated during the assimilation, which leads to a mismatch between the analyzed microphysical state variables and the microphysics scheme of the forecast model. In this study, the radar reflectivity is directly assimilated through an observation operator consistent with the DM Thompson microphysics scheme used in numerical integrations, and the impact of reflectivity operators based on SM and DM schemes on the analysis performance of the ensemble Kalman filter for typhoon Lekima on 9 August 2019 is evaluated. Reflectivity observations from a single operational weather radar in Wenzhou City, Zhejiang Province of China are assimilated. In addition, the dual-polarization observations from the same radar are used to evaluate the quality of the analysis. The analyzed reflectivity and dual-polarization characteristics obtained by different reflectivity operators are examined in detail. Compared with the experiments applying the reflectivity operator based on the SM Lin scheme, the use of a reflectivity operator consistent with the DM Thompson scheme adopted in the forecast model results in analyzed reflectivity and polarization characteristics that are more consistent with the observed characteristics in terms of general structure, location, and intensity. Forecasted reflectivity, 3 h accumulated precipitation, and typhoon intensity and track are also evaluated. The application of the reflectivity operator based on the DM scheme makes better forecasts of typhoon intensity, precipitation, and reflectivity, which also improves the forecast skills on typhoon tracks to a certain extent.

AcpAS: An Advanced Circularly Polarized Antenna Structure for an Airborne Relay Communication System

The airborne relay system is an important support for improving the stability of communication systems in complex electromagnetic environments. As a key component of the airborne relay system, the antenna needs to have characteristics such as high gain, dual circular polarization, wide beam coverage, and miniaturization. Based on the septum circular polarizer, this paper proposes a high-performance circularly polarized antenna structure suitable for airborne relay systems, named AcpAS. The structure consists of a coaxial feed port, a coaxial-to-waveguide transition, a septum circular polarizer, and a parabolic metal housing. Based on this structure, two antennas operating at 19.6 GHz to 21.6 GHz and 29.2 GHz to 31.2 GHz are designed in this paper. Simulated and measured results show that the two antennas have dual circular polarization characteristics, with beam coverage range of more than ±55° for gains higher than 0 dBi, and the radiation patterns exhibit good symmetry and wide-beam coverage characteristics.

Radar Survey of Hail-Producing Storms and Environments during the 2018–19 Severe-Weather Season in the Córdoba Region of Argentina

Abstract Frequent deep convective thunderstorms and mesoscale convective systems make the Córdoba region, near the Sierras de Córdoba mountain range, one of the most active areas on Earth for hail activity. Analysis of hail observations from trained observers and social media reports cross-referenced with operational radar observations identified the convective characteristics of hail-producing convective systems in central Argentina over a 6-month period divided into early (October–December 2018) and late seasons (January–March 2019). Reflectivity and dual-polarization characteristics from the Córdoba operational radar [Radar Meteorológico Argentina (RMA1)] were used to identify the convective modes of convective cells at time of positive hail indicators. Analysis of ERA5 upper-air and surface data examined convective environments of hail events and identified representative dynamic and thermodynamic environments. A majority of early season hail-producing cells were classified as discrete convection, while discrete and multicell occurrence evened out in the late season. Most hail-producing cells initiated directly adjacent to the Sierras in the late season, while cell initiation and hail production is further spread out in the early season. Dividing convective events into dynamic/thermodynamic regimes based on values of 1000 J kg−1 of CAPE and vertical wind shear of 20 m s−1 results in most early season events reflecting shear-dominant characteristics (low CAPE, high shear) and most late-season events exhibiting CAPE-dominant characteristics (high CAPE, low shear). Strength and placement of low-level temperature and moisture anomalies/advection and upper-level jets largely defined the differences in the dominant regimes. Significance Statement This study used regional radar data alongside hail reports from trained observers and social media to better understand the types and timing of storms identified as producing hail, given the lower resolution of satellite studies. Dividing the hail season (October–December; January–March) showed that within hail season, early season storms tended to be singular storms that formed across the region in environments with strong vertical winds and weak instability. Late-season storms were a mix of singular storms and multicellular storm systems focused on the mountains in weak vertical winds and strong instability. These results show differences from satellite studies and identify key representative hail-producing radar features and environmental regimes for this region, which could guide hail risk analysis within the severe-weather season.

Isolation enhancement of distinct element dual polarized compact MIMO antenna for 5G/WLAN application

AbstractA 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 (−12 dB) using substrate integrated waveguide stubs between inter‐ports and high isolation among the adjacent radiating elements (−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.

A high‐performance dual‐polarized corrugated horn for a compact antenna test range system

AbstractA high‐performance dual‐polarized horn antenna for a 5G millimeter wave compact antenna test range system (CATR) is proposed in this article. The feed antenna is mainly composed of a double‐ridged waveguide junction orthomode transducer (OMT), mode converter, and corrugated horn antenna. Among them, the OMT is the key device for the feed antenna to achieve dual polarization characteristics, and adopts a modular design method to apply the multi‐section impedance transformer in the vertical and horizontal polarization channels with good transmission characteristics. The corrugated horn antenna generates a symmetrical radiation pattern mainly in six corrugated slots. The proposed dual‐polarized corrugated horn antenna impedance matching bandwidth (VSWR < 2) is 24–50 GHz. Moreover, the measured gain is 10–12 dBi, and the measured cross‐polarization level is less than −30 dB within the operating frequency range. Meanwhile, the half‐power beamwidth radiation pattern in the whole operating band has a good symmetry and the beamwidth in both E‐ and H‐plane remains stable. As a practical application, the designed antenna is used as the feed of the CATR system. The measured results show that the amplitude distribution in the quiet zone (QZ) is within ±1 dB, the phase distribution is within ±8°, and the cross‐polarization isolation is better than 27 dB. The performance of the QZ is conducive to the use of the CATR system.

Dual-Wideband Dual-Polarized Magnetoelectric Dipole Antenna for Sub-6 GHz Applications

This letter presents a dual-wideband dual-polarized magnetoelectric dipole (ME) antenna, which works at the prominent frequency bands of 1.7 - 2.7 GHz and 3.3 - 5.0 GHz in Sub-6 GHz. A cross ME dipole excites dual-polarized radiation, and a cross-strip under the cross-dipole embeds a notched band from 2.7 - 3.3 GHz. Further, a cross-patch above the cross-dipole and a metal baffle around the ground improve the wideband impedance matching and stable the radiation pattern. As a result, a prototype of the proposed antenna is fabricated and measured. The measured results exhibit dual-wideband and dual-polarized characteristics of 1.66 GHz - 2.6 GHz (44.13%) and 3.12 GHz - 5.08 GHz (47.8%), 1.74 GHz - 2.64 GHz (41.09%) and 3.34 GHz - 5.08 GHz (42.08%), and the realized gains of 7 dBi and 9 dBi for the two ports, respectively. The proposed antenna is state-of-the-art for base-station applications in Sub-6 GHz.

Classification of Land Cover in Complex Terrain Using Gaofen-3 SAR Ascending and Descending Orbit Data

Synthetic aperture radar (SAR) image is an effective remote sensing data source for geographic surveys. However, accurate land cover mapping based on SAR image in areas of complex terrain has become a challenge due to serious geometric distortions and the inadequate separation ability of dual-polarization data. To address these issues, a new land cover mapping framework which is suitable for complex terrain is proposed based on Gaofen-3 data of ascending and descending orbits. Firstly, the geometric distortion area is determined according to the local incident angle, based on analysis of the SAR imaging mechanism, and the correct polarization information of the opposite track is used to compensate for the geometric distortion area, including layovers and shadows. Then, the dual orbital polarization characteristics (DOPC) and dual polarization radar vegetation index (DpRVI) of dual-pol SAR data are extracted, and the optimal feature combination is found by means of Jeffries–Matusita (J-M) distance analysis. Finally, the deep learning method 2D convolutional neural network (2D-CNN) is applied to classify the compensated images. The proposed method was applied to a mountainous region of the Danjiangkou ecological protection area in China. The accuracy and reliability of the method were experimentally compared using the uncompensated images and the images without DpRVI. Quantitative evaluation revealed that the proposed method achieved better performance in complex terrain areas, with an overall accuracy (OA) score of 0.93, and a Kappa coefficient score of 0.92. Compared with the uncompensated image, OA increased by 5% and Kappa increased by 6%. Compared with the images without DpRVI, OA increased by 4% and Kappa increased by 5%. In summary, the results demonstrate the importance of ascending and descending orbit data to compensate geometric distortion and reveal the effectiveness of optimal feature combination including DpRVI. Its simple and effective polarization information compensation capability can broaden the promising application prospects of SAR images.

A Group-Wise Feature Enhancement-and-Fusion Network with Dual-Polarization Feature Enrichment for SAR Ship Detection

Ship detection in synthetic aperture radar (SAR) images is a significant and challenging task. However, most existing deep learning-based SAR ship detection approaches are confined to single-polarization SAR images and fail to leverage dual-polarization characteristics, which increases the difficulty of further improving the detection performance. One problem that requires a solution is how to make full use of the dual-polarization characteristics and how to excavate polarization features using the ship detection network. To tackle the problem, we propose a group-wise feature enhancement-and-fusion network with dual-polarization feature enrichment (GWFEF-Net) for better dual-polarization SAR ship detection. GWFEF-Net offers four contributions: (1) dual-polarization feature enrichment (DFE) for enriching the feature library and suppressing clutter interferences to facilitate feature extraction; (2) group-wise feature enhancement (GFE) for enhancing each polarization semantic feature to highlight each polarization feature region; (3) group-wise feature fusion (GFF) for fusing multi-scale polarization features to realize polarization features’ group-wise information interaction; (4) hybrid pooling channel attention (HPCA) for channel modeling to balance each polarization feature’s contribution. We conduct sufficient ablation studies to verify the effectiveness of each contribution. Extensive experiments on the Sentinel-1 dual-polarization SAR ship dataset demonstrate the superior performance of GWFEF-Net, with 94.18% in average precision (AP), compared with the other ten competitive methods. Specifically, GWFEF-Net can yield a 2.51% AP improvement compared with the second-best method.

V-Band Dual-Polarized Filtering Transmitarray Antenna Enabled by a Planar Filtering Illumination Source

This article introduces a transmitarray antenna presenting excellent filtering and dual-polarization properties. Conventional transmitarrays resort to multilayered frequency-selective surfaces (FSSs) for filtering responses. In contrast, we propose a planar dual-polarized filtering antenna as an illumination source to enable a filtering transmitarray. The V-band dual-polarized filtering antenna is excited by a substrate integrated waveguide (SIW) feeding structure. By a novel trisection feed and a well-design radiating element, up to four radiation nulls are produced, leading to an excellent filtering response validated with experimental results. Subsequently, the antenna is employed to illuminate a phase-shifting surface (PSS), achieving outstanding filtering response, stable dual-polarization characteristics, low profile, and ease of integration. The proposed antenna and transmitarray demonstrate significant potential in V-band millimeter-wave (mmW) applications.

Wideband and dual‐polarized Twin Hilbert curve antennas for capsule endoscopy

AbstractIn this study, we design a pair of third‐order conformal Hilbert curve antennas for use in capsule endoscopy at three different bands (Industrial, Scientific, and Medical [ISM]), especially at 433 MHz, 915 MHz, and 2.45 GHz. The antennas are placed orthogonally with respect to each other, offering dual linear polarization characteristics, which have been highlighted in literature as the most robust communication link between a roaming transmitting capsule within the GI tract and the receiver antenna. The robustness of the link depends on (i) invariance of linear polarization with the position and orientation of the roaming transmitter, as well as (ii) tolerance of linearly polarized fields to depolarization effects when penetrated through the body. The antennas were manufactured on polyimide substrate, which was wrapped around a 3D‐printed capsule volume. Both antennas were measured inside bovine muscle tissue and the obtained results have been compared with the simulated results to validate the performance of the propose solution. The presented results showed that, the return loss characteristics and the measured bandwidth, for both antennas inside bovine muscle tissue, have matched with the simulated results. To the best of our knowledge, these demonstrated antennas are the first designed capsule antennas to address three ISM bands with dual linear polarization. The designed antennas can be adapted for clinical use with further development.

Dual‐polarized metasurface‐based monopole antenna design using characteristics mode theory for UHF RFID applications

In this research article, a printed dual-polarized metasurface (MTS) inspired printed monopole antenna using characteristics modes theory (CMT) is investigated for UHF RFID applications. A T-shaped monopole with U-shaped asymmetric stubs is designed to generate circular polarization (CP) radiation traits. The grounded MTS layer is constructed with array of unit cells and fixed at air-gap of λo/4 with reference to the monopole radiator (λo is free-space wavelength at CP frequency band, 945 MHz), offering good impedance bandwidth (IBW), stable CP boresight radiation gain, and high radiation efficiency. By using CMT, interpretation of CP characteristics is highlighted, that is, the resonating modes exhibit asymptotic nature at the designated CP band with symptotic nature above and beyond the designated operating bands. Dual-polarized characteristics are observed in both principal planes, due to the effect of grounded MTS loading. The prototype antenna of 0.315λo × 0.315λo is designed and validated. It operates from 836 to 1066 MHz with 24.18% IBW, 5.23% 3-dB axial ratio bandwidth (ARBW) from 905.1 to 950 MHz and attains >6.8 dBic as a CP peak gain with the total efficiency of >83%. Prior to the attainment of good CP attributes in UHF RFID bands, it can be used for RF energy harvesting and wireless power transmission.

Wideband dual‐polarized wide solid angle scanning cylindrically conformal millimeter‐wave phased array

A dual-polarized substrate-integrated hollow antenna (SIHA) and its cylindrically conformal phased array are proposed. The bandwidth of the proposed SIHA is 35%. The cylindrically conformal phased array with 24 SIHA subarrays can scan its beam in the whole horizontal plane and scan its beam within ± 60° in the vertical plane. The proposed array with wide band, wide-angle scanning, and dual-polarization characteristics is appropriate for millimeter-wave base station applications.

TWELVE-PORT DUAL-POLARIZED DUAL-BAND MIMO ANTENNA FOR FIFTH-GENERATION MOBILE DEVICES

This research article presents a twelve-port dual-band MIMO antenna for 5G and WLAN-enabled user equipment with dual-polarization characteristics. Both the operating frequencies are of sub-6GHz band centered at 3.6GHz and 5.5GHz respectively that are also independent of each other. Antenna polarizations depend on the excitation of the feed elements on the substrate. The antenna is designed using CST Studio Suite and fabricated on low-cost FR-4 substrate to ensure its easy availability and keep it cost-effective. The radiation pattern acquired for the proposed antenna is bi-directional with good gain and efficiency. The simulation results are in good covenant with experimental results.

CMA assisted 4-port compact MIMO antenna with dual-polarization characteristics

In this paper, Characteristics mode analysis (CMA) is introduced to study the dual-polarization behavior of simple monopole antenna. The antenna consists of monopole feed with symmetric arms (SA), resonating at 2.45 GHz and right-handed stub (RHS) is connected to resonate at 5.8 GHz. The SA has linear polarization and RHS has circular polarization. CMA is introduced to explore dual-polarized properties and validated on modal metrics. The intuition of antenna design is further extended to 4-port MIMO antenna configuration. Due to rotationally symmetrical connected ground topology, another induced resonance at 1.54 GHz is observed. A L-shaped stub is further connected to one-end of the monopole arm of each antenna element, that function as 2.5 GHz resonator and an effective isolator. The overall antenna dimension is 0.3λ× 0.3λ× 0.018λ (where λ is the lowest operating wavelength) and the elements are spatially separated with edge-to-edge spacing of 0.018λ with port isolations >15 dB. The MIMO antenna operates at 1.54 GHz, 2.5 GHz with linear polarization and at 5.63 GHz as circular polarization. The antenna gains with radiation efficiencies are 0.62 dBi (>60%), 4 dBi (>70%) and 4.25–6 dBc (>80%). The computed ECCfar−fields is < 0.3, showing its potential for pattern and polarization diversity MIMO environments. A prototype antenna is fabricated and measured with good agreements and found compatible for L-band, lower WLAN and upper WLAN applications.

Multifunctional Tri-Band Dual-Polarized Antenna Combining Transmitarray and Reflectarray

A multifunctional tri-band antenna combining transmitarray (TA) and reflectarray (RA) is presented in this communication. Five-layer patches etched on three dielectric substrates with two air gaps are used as the unit cell. Cross dipoles inserted in cross slots control transmission characteristics at Ku-band (14 GHz). Double square rings on the top and bottom layers control reflection characteristics at K (21 GHz)- and Ka (30 GHz)-bands, respectively. The antenna has dual-polarized characteristics in each band. The phase shift range that can be obtained is 360° for 3 dB transmission magnitude at Ku-band and 0.15 dB reflection magnitude at K- and Ka-bands. The tri-band dual-polarized TA/RA antenna is designed, manufactured, and measured to verify the performance. The simulated results keep consistent with the measured ones. The measured results show that the TA has a peak gain of 23.8 dBi with an aperture efficiency of 40% at 14.25 GHz and 1 dB gain bandwidth of 6.5%. The RA has a peak gain of 28 dBi with an aperture efficiency of 44% at 21 GHz and 1 dB gain bandwidth of 7.3%, and has a peak gain of 31.5 dBi with an aperture efficiency of 47% at 30.5 GHz and 1 dB gain bandwidth of 7.1%.

Wearable Dual-Band Dual-Polarization Button Antenna for WBAN Applications

This letter proposes a wearable dual-band dual-mode button antenna for wireless body-area network applications. It covers the 2.45 and 5.8 GHz Industrial, Scientific, and Medical bands. The two operating modes of the antenna are designed to share a common radiator with different functionalities for distinctive communication requirements. The antenna operates from 2.32 to 2.57 GHz as a top-loaded monopole antenna with linear polarization, which is applicable for on-body communications due to its omnidirectional radiation pattern. In contrast, it works as a crossed-dipole antenna in its higher operation band extending from 5.72 to 7.85 GHz, in which it exhibits broadside radiation with circular polarization suitable for off-body communications. The experimental characterization on the fabricated antenna prototype, both in free space and proximity to the human body, proves that the antenna operates as anticipated with dual-band and dual-polarization characteristics for wearable applications.

Design of a Dual-Beam Dual-Polarized Offset Parabolic Reflector Antenna

In this paper, an offset reflector antenna with dual-beam and dual-polarization characteristics is developed to provide the angular diversity function for troposcatter communication system. The antenna system consists of a parabolic reflector and a dual-beam feed. For the dual-beam feed, two identical Ku-band feed elements are arranged side by side to generate two beams toward the reflector. The two beams are substantially nonoverlapping. The feed element is composed of a dielectric rod, a square waveguide, and an ortho-mode transducer. The dielectric rod is effective in reducing the beamwidth of the feed and providing more tapered illumination on the reflector in order to increase the antenna gain. Moreover, the developed antenna is able to produce two independent beams with the vertical and horizontal polarizations. The antenna was fabricated and tested with good agreement between the simulation and measurement results. The measured voltage standing wave ratios of the four feed ports are less than 1.5:1, and the beam separation angle is not more than 0.7° or about one time half-power beamwidth, and the antenna gain is higher than 45 dBi over the operating band from 14.5 to 15.35 GHz.

A dual-polarized reflector antenna with λ/2 printed dipoles for femtocell applications

A printed dipole antenna with reflector features a high gain. Accordingly a dual-polarized reflector antenna with high gain for base transceiver stations (BTS) is proposed. Design of this antenna is based on λ/2 printed dipoles supplied through Γ-shaped microstrip feed lines. The basic structure of the antenna is composed of two orthogonal radiating elements which are separately printed on two substrates. Each element has a λ/2 printed dipole on one side of the substrate and a 50 Ω Γ-shaped microstrip feed line on the other side. The combination of these two orthogonal radiating elements provides proper ± 45̂ dual-polarized characteristics for BTS applications. The radiating elements are placed on an aluminum slot reflector with side walls in order to make the antenna directional, and to increase the gain and the fron to back ratio (FBR) as well. A prototype of this antenna is manufactured and it covers the frequency range of 1.4–2.6 GHz due to the measured results. The average measured gain and half-power beamwidth (HPBW) are obtained 8.35 ± 0.55 dBi and 165̂, respectively.

Radar cross section reduction metasurfaces based on phase gradient and chessboard structure

In this article, wideband radar cross section (RCS) reduction metasurface is proposed. The unit of the metasurface is consisted of a noncentral symmetry hexagon patch with 2 semi-circular slots at the symmetric corners. As a result, the unit has an anisotropic response for x- and y-polarized wave. The reflection phase is varied with the radius of slots. The range of phase variation is extended by rotation of the unit with 90°. According to the generalized Snell's Law, 4 different phase gradient supercells with dual polarization characteristics and different gradient directions are obtained. To improve the RCS reduction, chessboard structure is used. By combining these 2 technological approaches, a wideband, polarization insensitive RCS reduction is designed, which can reflect the electromagnetic wave uniformly. Both numerical and measured results show that it enables to realize a 10 dB RCS reduction in a wideband from 8.5 to 13 GHz.

A Dual-Broadband, Dual-Polarized Base Station Antenna for 2G/3G/4G Applications

A base station antenna with dual-broadband and dual-polarization characteristics is presented in this letter. The proposed antenna contains four parts: a lower-band element, an upper-band element, arc-shaped baffle plates, and a box-shaped reflector. The lower-band element consists of two pairs of dipoles with additional branches for bandwidth enhancement. The upper-band element embraces two crossed hollow dipoles and is nested inside the lower-band element. Four arc-shaped baffle plates are symmetrically arranged on the reflector for isolating the lower- and upper-band elements and improving the radiation performance of upper-band element. As a result, the antenna can achieve a bandwidth of 50.6% for the lower band and 48.2% for the upper band when the return loss is larger than 15 dB, fully covering the frequency ranges 704-960 and 1710-2690 MHz for 2G/3G/4G applications. Measured port isolation larger than 27.5 dB in both the lower and upper bands is also obtained. At last, an array that consists of two lower-band elements and five upper-band elements is discussed for giving an insight into the future array design.