Surface Current Analysis Research Articles

Decomposition of Submesoscale Ocean Wave and Current Derived from UAV-Based Observation

The consecutive submesoscale sea surface processes observed by an unmanned aerial vehicle (UAV) were used to decompose into spatial waves and current features. For the image decomposition, the Fast and Adaptive Multidimensional Empirical Mode Decomposition (FA-MEMD) method was employed to disintegrate multicomponent signals identified in sea surface optical images into modulated signals characterized by their amplitudes and frequencies. These signals, referred to as Bidimensional Intrinsic Mode Functions (BIMFs), represent the inherent two-dimensional oscillatory patterns within sea surface optical data. The BIMFs, separated into seven modes and a residual component, were subsequently reconstructed based on the physical frequencies. A two-dimensional Fast Fourier Transform (2D FFT) for each high-frequency mode was used for surface wave analysis to illustrate the wave characteristics. Wavenumbers (Kx, Ky) ranging between 0.01–0.1 radm−1 and wave directions predominantly in the northeastward direction were identified from the spectral peak ranges. The Optical Flow (OF) algorithm was applied to the remaining consecutive low-frequency modes as the current signal under 0.1 Hz for surface current analysis and to estimate a current field with a 1 m spatial resolution. The accuracy of currents in the overall region was validated with in situ drifter measurements, showing an R-squared (R2) value of 0.80 and an average root-mean-square error (RMSE) of 0.03 ms−1. This study proposes a novel framework for analyzing individual sea surface dynamical processes acquired from high-resolution UAV imagery using a multidimensional signal decomposition method specialized in nonlinear and nonstationary data analysis.

Broadband metasurface bandpass filter with wide angular stability for the Ku-band

Broadband spatial spectral filters have consistently been in high demand due to their diverse and extensive applications across numerous fields in the past decades. In this paper, a broadband metasurface (MS) bandpass filter (BPF) with wide angular stability was proposed and investigated at Ku band. The unit-cell of the proposed MS BPF is consisted of the cross-shape structure (CSS) sandwiched with two layer identical four-square-patches (FSPs) and dielectric substrates. Finite element method (FEM) simulation indicates that the designed MS BPF has distinctive broadband transmission coefficient of over −3 dB from 12.75 GHz to 16.8 GHz with a relative bandwidth of 27.4 %, which is basically consistent with equivalent circuit model (ECM) calculation. The physical mechanism underlying the proposed MS BPF is elucidated through the introduction of impedance matching theory, electric field and surface current analysis. Further numerical simulation has confirmed that the designed broadband MS BPF exhibits valid performance across a wide spectrum of incident angles, encompassing both transverse electric (TE) and transverse magnetic (TM) polarizations. Finally, a prototype has been fabricated for measurements, and the proposed design has been validated through comprehensive analysis of simulated and measured results. Due to its excellent transmission properties, the proposed MS BPF shows potential application in such as radar, remote sensing, and satellite communication.

A 4-port flexible MIMO antenna with isolation enhancement for wireless IoT applications

This paper presents a conformal, miniaturized, and geometrically simple monopole antenna designed for Vehicle–to–Everything (V2X) communications. The antenna consists of a flexible substrate, radiating patch, ground, and metallic stubs. Meandered lines are added to the U-shaped radiator to achieve the required bandwidth of the antenna. The antenna has |S11|< −10 dB magnitude from 5.06 to 7.24 GHz, attaining a peak low magnitude of–68 dB. The antenna is configured into a 4-port Multiple–Input–Multiple–Output (MIMO) setup to minimize the mutual coupling between its elements. The proposed flexible MIMO antenna offers bandwidth from 5.37 to 7.34 GHz and a peak moderate gain of 4.63 dBi with omnidirectional stable radiation patterns. To improve the mutual coupling, two hollow concentric circular structures, in combination with a pair of stub networks are integrated between the elements of the MIMO system. The transmission coefficient and surface current analysis confirm the effectiveness of the decoupling structure. The presented MIMO antenna is characterized by high isolation, a low envelope correlation coefficient (ECC), and high diversity gain, suitable for V2X MIMO communication scenarios.

Wideband Circularly Polarization and High-Gain of a Slot Patch Array Antenna Realized by a Hybrid Metasurface.

In this paper, a patch array antenna with wideband circular polarization and high gain is proposed by utilizing a hybrid metasurface (MS). A corner-cut slotted patch antenna was chosen as the source due to the possible generation of CP mode. The hybrid MS (HMS), consisting of a receiver MS (RMS) arranged in a 2 × 2 array of squared patches and a linear-to-circular polarization conversion (LCPC) MS surrounding it was then utilized as the superstrate driven by the source. The LCPC MS cell is a squared-corner-cut patch with a 45° oblique slot etched, which has the capability for wideband LCPC. The LCPC unit cell possesses wideband PC capabilities, as demonstrated by the surface current analysis and S-parameter simulations conducted using a Floquet-port setup. The LP EM wave radiated by the source antenna was initially received by the RMS, then converted to a CP wave as it passed through the LCPC MS, and ultimately propagated into space. To further enhance the LCPC properties, an improved HMS (IHMS) was then proposed with four cells cut at the corners, based on the original HMS design. To verify this design, both CMA and E-field were utilized to analyze the three MSs, indicating that the IHMS possessed a wideband LCPC capability compared to the other two MSs. The proposed antenna was then arranged in a 2 × 2 array with sequential rotation to further enhance its properties. As demonstrated by the measurements, the array antenna achieved an S11 bandwidth of 60.5%, a 3 dB AR bandwidth of 2.85 GHz, and a peak gain of 15.1 dBic, all while maintaining a low profile of only 0.09λ0.

Intercomparison of tropical Indian Ocean circulation in ocean reanalysis and evaluation in CMIP6 climate models

In the present study, we assess the Tropical Indian Ocean (TIO) circulation features from the available ocean reanalysis products and the latest version of Coupled Model Intercomparison Project (CMIP6) climate model simulations. We considered the following reanalysis products; Ocean Reanalysis System 5 (ORAS5), Estimating the Circulation and Climate of the Ocean (ECCO), Global Ocean Data Assimilation System (GODAS), Ensemble Coupled Data Assimilation (ECDA), the Bluelink Reanalysis (BRAN) and Simple Ocean Data Assimilation (SODA) and compared them against in-situ observations and the satellite-derived Ocean Surface Current Analyses Real-time (OSCAR). The reanalysis products underestimate the strength and location of the Wyrtki Jets. The BRAN reanalysis performed well compared to the other products in representing the TIO surface zonal currents, followed by ORAS5. The vertical extension of subsurface zonal currents in the equatorial Indian Ocean and their seasonal maxima are well captured in ORAS5. Thus, our analysis suggests that the ORAS5 is a qualitative product to estimate the TIO circulation. We further evaluated the TIO current patterns simulated by CMIP6 models with in-situ data/ ORAS5. The majority of the models show discrepancies in simulating equatorial and south equatorial current systems with a mean bias of 0.1cms−1 and 0.2cms−1, respectively. NorESM2-MM, NorESM2-LM, CanESM5, CESM2-WACCM-FV2, and E3SM-1-ECA models showed a superior skill in reproducing the TIO circulation compared to the rest of the models. Our analysis highlights the importance of assessing various reanalysis products and coupled climate models in representing the circulation of the TIO and, consequently, their role in depicting regional weather and climate.

Dumbbell shaped structure loaded modified circular ring resonator based perfect metamaterial absorber for S, X and Ku band microwave sensing applications

In this paper, a new metamaterial absorber (MMA) is presented that exhibits peak absorptions at 3.26 GHz, 11.6 GHz, and 17.13 GHz within S, X, and Ku bands. The unit cell of the proposed MMA is constructed on an FR4 substrate having an electrical dimension of 0.144λ × 0.144λ, where wavelength, λ is calculated at the lowest absorption frequency. The unique structural design of the unit cell consists of two concentric copper rings with which dumbbell-shaped structures are attached. The rotating symmetrical structural design of this MMA provides around 93.8%, 96.47%, and 99.95% peak absorptance in the mentioned frequencies, which is invariable with the change of incident angle as well as polarization angle. The metamaterial properties of the proposed absorber are studied along with the surface current analysis. The MMA shows single negative behaviour and it also exhibits high-quality factors (Q factor) of 21.73, 41.42, and 51.90 at maximum absorptance frequencies. The MMA is analysed by it's equivalent circuit to understand the resonance phenomenon, which is verified through simulation in Advanced Design Systems (ADS) software. The testing is done on the developed prototype of the proposed MMA. Measurement results are in close proximity to the simulation results. Due to its high Q factor, high EMR, and insensitivity to polarization and angle of incidence, it can be utilized as a part of miniaturized microwave device. In addition, the proposed MMA can exhibit high sensing performance and flexibility to differentiate different oils in S, X, and Ku bands.

Low-RCS electromagnetic metasurface antenna based on shared-aperture technique

In this paper, a novel shared-aperture method of electromagnetic metasurface and antenna is proposed to obtain low radar-cross-section (RCS) performance. In this method, the low-RCS metasurface is first designed, then this metasurface is combined with traditional antenna to obtain novel low-RCS antenna based on shared-aperture technique. Besides, the analysis and corresponding local structure modification are also conducted to ensure that the antenna has good radiation performance while reducing broadband RCS. Using this method, a dual-layer polarization rotation unit cell is first proposed and its broadband working principle is investigated by both theoretical analysis and numerical comparison. Based on this unit cell, a broadband low-RCS metasurface is constructed. Then an initial shared-aperture metasurface antenna is obtained by substituting the middle cells in the metasurface with traditional patch antenna directly. Through careful analysis of surface current in radiation mode, the gain decrease of this metasurface antenna is revealed. On this basis, a finite removal strategy is put forward and some metasurface cells in the antenna are removed by using the electric current analysis. Consequently, an improved shared-aperture metasurface antenna is proposed. This improved antenna works in a frequency range from 6.3 to 7.48 GHz, which is slightly wider than the traditional patch antenna. Its gain is also higher than that of traditional antenna, with a maximum improvement of 1 dB. Meanwhile, the apparent RCS decreases from 6 to 16 GHz for any polarized incident wave, and the reduction peak is larger than 20 dB. Finally, fabrications and measurements are conducted. The measurement results and numerical calculations are in good agreement. The well-behaved radiation performance and broadband low-RCS property of this metasurface antenna verify the effectiveness of the proposed method. Unlike most of reported design methods of low-RCS antennas directly from traditional antennas, the proposed method adopts reverse thinking to transform scattering optimization into radiation optimization, realizing the integration between metasurface and antenna, thus making low-RCS antenna design easier and faster.

Dual-Band Metamaterial Microwave Absorber using Ring and Circular Patch with Slits

This paper proposes a dual-band metamaterial microwave absorber operating at 2.5 GHz and 5.8 GHz. The absorber consists of a ring and a circular patch with slits resonator structures printed on a FR4 dielectric substrate backed by a ground layer. The main advantage of the absorber lies in its design flexibility in which each absorption band is independent and can be individually tuned by changing the dimensions of each resonator structure. The absorber unit cell is simulated and parametrically optimized using Computer Simulation Technology (CST) software. The absorption mechanism is analyzed through surface current analysis. The absorber prototype, with dimensions of 200 × 200 × 1.6 mm3 and consisting of an array of 7 × 7 unit cells, is fabricated and experimentally investigated using antennas in free-space measurement. The absorber exhibits over 97% absorption at both resonance frequencies. Furthermore, the absorber is demonstrated to be applicable in sensing applications for dielectric constant determination. With its design simplicity, wide-angle receptive, and polarization insensitive behavior, it is envisaged that the proposed absorber will find practical use in absorbing and sensing applications.

Approximation of High Intensity Radiated Field by Direct Current Injection using matrix methods based on Characteristic Mode Analysis

Abstract. This contribution discusses the approximation of radiated by conducted immunity tests by the example of High Intensity Radiated Field (HIRF) and Direct Current Injection (DCI) based on a surface current analysis. For this purpose, Characteristic Mode Analysis (CMA) is applied to provide basis functions for a surface current expansion in Characteristic Modes. Via a matrix-based basis transformation algorithm involving Characteristic Mode data of both HIRF and DCI test setups, suitable DCI surface currents are derived. The approximation of HIRF surface currents by the computed DCI surface currents is analyzed for exemplary DUTs over a broad frequency range. Within this frequency range, those DCI frequencies leading to an optimal approximation of the HIRF current are determined. Concerning practical issues in DCI testing, the influence of DCI adapter parameters on the surface current approximation is elucidated. The numerical results show that DCI can approximate HIRF at low frequencies largely independent from the DCI adapter setting, whereas at high frequencies an approximation is difficult to realize.

Superstatistical analysis of sea surface currents in the Gulf of Trieste, measured by high-frequency radar, and its relation to wind regimes using the maximum-entropy principle

Abstract. Two years (2021–2022) of high-frequency-radar (HFR) sea surface current data in the Gulf of Trieste (northern Adriatic Sea) are analysed. Two different timescales are extracted using a superstatistical formalism: a relaxation time and a larger timescale over which the system is Gaussian. We propose obtaining an ocean current probability density function (PDF) combining (i) a Gaussian PDF for the fast fluctuations and (ii) a convolution of exponential PDFs for the slowly evolving variance of the Gaussian function rather than for the thermodynamic β=1/σ2 in a system with a few degrees of freedom, as the latter has divergent moments. The Gaussian PDF reflects the entropy maximization for real-valued variables with a given variance. On the other hand, if a positive variable, as a variance, has a specified mean, the maximum-entropy solution is an exponential PDF. In our case the system has 2 degrees of freedom, and therefore the PDF of the variance is the convolution of two exponentials. In the Gulf of Trieste there are three distinct main wind forcing regimes: bora, sirocco, and low wind, leading to a succession of different sea current dynamics on different timescales. The universality class PDF successfully fits the observed data over the 2 observation years and also for each wind regime separately with a different variance of the variance PDF, which is the only free parameter in all the fits.

Validation of OSCAR Surface Currents in the Western Arctic Marginal Seas Against Saildrone Observations

AbstractThe western Arctic marginal seas undergo large seasonal variation, but are very challenging to observe directly due to sea ice and shallow depths. Deployments of several saildrone uncrewed surface vehicles in the summers of 2018 and 2019 provided unique opportunities to validate the satellite‐derived near surface currents, Ocean Surface Current Analysis Real‐time (OSCAR), in the western Arctic marginal seas against in situ upper ocean current measurements. Overall, OSCAR current is biased low (by 5.3 cm/s) with significant noise. Higher vector correlation estimated by the cosine similarity and speed differences often occur where stronger currents (often topography‐steered) are observed. Such differences reveal that the data set resolvability depends on spatial and temporal resolutions, smoothing, and latitudes, suggesting that OSCAR is able to depict the major current systems but significantly underestimates their strength. Poorer vector correlation occurs at weaker current regimes (&lt;10 cm/s), over the shallow Hanna Shoal, near fresher water due to ice melt and river discharge. The latter two water class regimes highlight the importance of salinity contribution to the buoyancy force which is neglected in the OSCAR formulation.

Dual-band dual-polarized MIMO design for vehicular applications

A low-cost dual-band dual-polarized Multiple input–Multiple out (MIMO) antenna system is proposed. The proposed configuration is based on a singly fed single-layer patch antenna, working in the 4400-5000 MHz and 5925-7125 MHz frequency bands. Based on surface current analysis, dual-band dual-polarized operation is achieved through structure modification by cutting the edges of the patch and adding a slot. A size reduction of 24.08% is achieved in the lower frequency band. The radiation mechanism of the antenna is explained using characteristics mode analysis. The proposed design has a similar radiation characteristic in both bands along with orthogonal linear polarization. The minimum axial ratios of 18.23 dB and 12 dB are observed in both bands. The proposed 4-element MIMO antenna system has a compact size of 40.3 mm × 40.3 mm × 1.6 mm, minimum inter-element isolation of −20 dB, and an optimal envelope correlation coefficient value of 0.03, hence making it a suitable candidate for future Internet of Vehicles applications.

Modified combination of triple split ring resonator based triple band single negative metamaterial for satellite applications

This paper investigates a modified combination of triple split ring resonator (SRR) based triple band single negative metamaterial for satellite applications. The proposed unit cell structure has a triple split ring resonator i.e. square, circular and rhombus shape. The lower plane completely encloses the FR-4 substrate with a thickness of 1.6 mm, on top of which the metallic resonating structure with thickness of 0.035 mm is attached. The structure provides quad band resonances of transmission coefficient (S21) at 2.02 (S-band), 6.77 (C-band), and 13.22 (Ku-band) GHz with magnitude of -27.8, -23.2, and -27.2 dB, respectively and also offers the wider bandwidth. The plot of relative permittivity, permeability, refractive index and impedance is used to explain the metamaterial behavior. Additionally, a plot of the electromagnetic field and surface current analysis for a separate frequency that belongs to the S, C, and Ku band makes the unit cell structure to help illustrate the metamaterial behavior. The effective medium ratio (EMR) of the structure is 14.85, demonstrating its compactness. The performance of the structure is validated through the simulation result using CST Microwave Studio and HFSS simulator. The suggested structure will be a possible option for satellite communication (S, C and Ku-band) because of wider bandwidth and excellent EMR.

Retrieval of 2-D Ocean Total Surface Current From Sentinel-1 Doppler Frequency Shift Using 2-D Kalman Filtering

Synthetic aperture radar (SAR) has all-weather, all-day, large-area observation capability and can measure ocean total surface currents with Doppler frequency shift. However, conventional SAR can only obtain the radial velocity of the ocean total surface current. In this letter, we propose a method for inverting ocean total surface current vectors using a two-dimensional (2D) Kalman filter and a priori information about ocean current fields from Ocean Surface Current Analyses Real-time (OSCAR). We establish a complete filtering process including filter creation, filtering path selection and fusion of filtering results. We construct the Kalman filter according to the motion characteristics of ocean currents and transform the ocean surface current vector inversion problem into a filtering problem. The introduction of two-dimensional filtering can better adapt to the directionality of ocean currents. Furthermore, we design the filtering path to obtain smoother filtering results. In order to synthesize the filtering results of different filtering paths, we use the Covariance Intersection (CI) fusion method in distributed fusion to obtain the final ocean current vector inversion results. The accuracy of the inversion is verified by the measured data. The Root Mean Square Error (RMSE) of the proposed method with the mean Doppler error of 5.43Hz is 0.182 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m/s</i> in eastward speed and 0.141 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m/s</i> in northward speed. The reduction is 0.009 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m/s</i> and 0.029 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m/s</i> against OSCAR.

Spatio-temporal monitoring of the iceberg D28 using SCATSAT-1 data

Abstract The study of the icebergs and their movements is one of many applications of scatterometer data in the study of the ecosystems of polar regions. SCATSAT-1 is the Indian Space Research Organisation’s (ISRO’s) Ku-band (13.515625 GHz) scatterometer. Using enhanced resolution Gamma0H (horizontally polarised incidence angle normalised backscattering coefficient) data of SCATSAT-1, we observed the movement of iceberg D28 and its interaction with wind, ocean currents and sea ice for one and a half years of its journey (JD 269, 2019 to JD 051, 2021). The data sets used are as follows: (1) SCATSAT-1 level-4 Gamma0H; (2) OSCAR (Ocean Surface Current Analysis Real-time) third-degree resolution ocean surface currents; (3) hourly wind speed data of ERA5; 4) NSIDC (National Snow and Ice Data Center) sea ice concentration data; and (5) NSIDC Polar Path-finder Daily EASE-Grid Sea Ice Motion Vectors, Version-3. For this study, we divide the continent into five different regions/sectors. It is found that the trajectory of the iceberg is influenced by the resultant of the wind and ocean current, at different scales in these regions. Moreover, sea ice motion can also change the course of iceberg. From the on-screen digitisation of the iceberg, the average area of the iceberg is found to be approximately 1509.82 km2 with approximate dimensions of 27 km × 55.5 km. We conclude that spatial and temporal behaviours of the iceberg can be ascertained from the scatterometer data.

Temperature-Adaptive reconfigurable chiral metamaterial for tailoring circular dichroism based on shape memory alloy

Self-adaptable materials with autonomous morphological transformation by sensing environmental changes have emerged as one of the most promising but challenging approaches for various chiral devices. Unlike previous work on reconfigurable chirality through human intervention, we proposed a temperature-adaptive chiral meta-device. It can autonomously sense the environment and manipulate the optical chirality through 3D-to-3D morphological transformation. As a proof of concept, a 3D morphable chiral meta-device was designed with shape memory alloy (SMA), resulting in reconfigurable circular dichroism (CD). The curving direction of SMA enables the meta-device to switch between left-handed, right-handed, and non-chirality by sensing environmental temperature. The analysis of surface currents and CD spectra reveals that the underlying physical mechanism behind the chirality originates from the surge of toroidal and electric quadrupole dipole moments. Simultaneously, the spin-to-orbital angular momentum conversion is realized based on the Pancharatnam-Berry phase, where the topological charge is modulated by the environmental temperature. Encouragingly, this work paves the way for the self-adaptive chiral meta-devices with 3D morphological transformation and can be applied to a series of novel photon-spin-selective devices for optical communication and biosensing.

Simulation of Marine Debris Path Using Mathematical Model in the Gulf of Thailand

Marine debris is an important environmental problem that affects aquatic animals, ecosystems, economy, society, and humans. This research aims to simulate the path of marine debris in the Gulf of Thailand using a mathematical model that includes two models: the Oceanic Model (OCM), which is based on the Shallow Water Equations (SWE), and the Lagrangian Particle Tracking (LPT) model. The OCM is the partial derivative equation system solved by the finite difference method to satisfy the Arakawa C-grid and the splitting method. The LPT model includes the current velocity, wind velocity at 10 m above sea level, random walk term, and the buoyancy ratio of marine debris with six cases, which are 100:1, 10:1, 1:1, 0:1, 1:10, and 1:100. The current velocity from OCM is applied to the LPT model. This research uses a garbage boat that capsized near Koh Samui on 1 August 2020 as a case study. The simulated current velocity of OCM is compared with Ocean Surface Current Analyses Real-time (OSCAR) data. The Root Mean Square Error (RMSE) of u-velocity is 0.070 m/s, and that of v-velocity is 0.058 m/s. The simulation of the marine debris’s path from the LPT model demonstrates the movement to Koh Samui, Koh Taen, Koh Wang Nai, Koh Wang Nok, Koh Rap, the east coast of Nakorn Si Thammarat province, Phu Quoc Island of Vietnam and the middle of the Gulf of Thailand with the different buoyancy ratios and time durations.

Comprehensive Characterization of an Ellipsoidal Cylinder Calibrator for Radar Cross Section Measurement

Currently, a set of scaled squat circular cylinders (SCCs) have been widely used for co-polarimetric radar cross section (RCS) calibration in various test ranges where low RCS metal pylons are used. The major drawback of a circular cylinder (CC) is its high sensitivity to elevation angle, as well as the frequency-dispersive theoretical RCS. In this work, we propose a new RCS calibrator, the metal ellipsoidal cylinder (EC), whose RCS characteristics are similar to a metal sphere, while it can be mounted on a metal pylon with little electromagnetic (EM) interactions as a CC does. A high-frequency RCS expression is derived using geometrical optics (GO) for the new calibrator. The scattering mechanisms are analyzed to establish the accurate parametric representation of the theoretical RCS. Based on surface current analysis and numerical calculation, the calibrator-pylon interaction (CPI), the angular sensitivity, and the bistatic RCS characteristics are discussed, enabling the calibration uncertainty evaluation for applying the proposed calibrator in the ground-plane range (GPR). Numerical and experimental results of a manufactured squat EC (SEC) are presented to demonstrate the excellent performance of the proposed EC calibrator for co-polarimetric RCS calibration.

Novel Electromagnetic Characterization Methods for New Materials and Structures in Aerospace Platforms.

The tendency over the last decades in the aerospace industry is to substitute classic metallic materials with new composite materials such as carbon fiber composites (CFC), fiber glass, etc., as well as adding electronic devices to ensure the safety and proper platform operation. Due to this, to protect the aircraft against the Electromagnetic Environmental Effects (E3), it is mandatory to develop accurate electromagnetic (EM) characterization measurement systems to analyze the behavior of new materials and electronic components. In this article, several measurement methods are described to assess the EM behavior of the samples under test: microstrip transmission line for a surface current analysis, free space to obtain intrinsic features of the materials and shielding effectiveness (SE) approaches to figure out how well they isolate from EM fields. The results presented in this work show how the different facilities from the National Institute of Aerospace Technology (INTA) are suitable for such purposes, being capable of measuring a wide variety of materials, depending on the type of test to be carried out.

High‐gain and wideband differentially fed circularly polarized planar aperture antenna

AbstractA novel circularly polarized (CP) planar aperture antenna that is completely self‐designed and manufactured with high gain and wideband is proposed in this paper. The antenna adopts a differential feed network so that the energy is evenly transmitted to the radiation patch. By surface current analysis, the closed loop with linearly polarized (LP) characteristics is changed into two arms of different lengths to generate CP radiation. The uniformity and symmetry of energy improve the wideband and high‐gain performance of the antenna. The fabricated antenna prototype has the characteristics of a wideband of 33.3% (28.1–39.3 GHz) and an average gain of 11.4 dBic, which could achieve 3‐dB axial ratio bandwidth of 12.4% (35.2–39.6 GHz) and a stable left‐handed CP and radiation patterns throughout the operating bandwidth with a peak gain of 15.8 dBic.