This letter presents miniaturized Gysel power dividers using lumped-element components. The characteristic impedances of all the equivalent transmission lines in these dividers are fixed to the same values based on even and odd mode analysis, thus simplifying the design procedure and miniaturizing the Gysel power dividers. The ideal divider designed at a frequency of 590 MHz exhibits power splits of -3.2±0.2 dB and return losses of greater than 15 dB for the frequency range of 460 to 650 MHz. Furthermore, isolation between output ports is greater than 15 dB for the frequency range of 500 to 680 MHz. The fabricated miniaturized Gysel power divider achieves broadband characteristics and is very compact, occupying only about 15% of the area of a conventional Gysel power divider.

Remote sensing has been used widely in studying the earth terrain such as snow or sea ice due to its fast, convenient and long-term monitoring capabilities. SAR images acquired could be used to analyze the condition of snow, snow water equivalent (SWE), surface roughness and others. Theoretical models have also been developed to understand how microwave interacts with the snow medium and the scatterers embedded inside the medium. Conventionally, spherical shape of scatterers is commonly used to represent the ice particles embedded inside snow where the actual shape of scatterers can vary. This paper is to present a theoretical model based on radiative transfer formulation that utilizes computational electromagnetics in the modelling of scattering from arbitrary shape of scatterers. The paper also studies the effect of scatterer shape on scattering mechanisms and total backscattering coefficient. Numerical solution of Relaxed Hierarchical Equivalent Source Algorithm (RHESA) was integrated with existing radiative transfer theoretical model to simulate a layer of random discrete snow medium. Several shapes of scatterers were simulated, and theoretical simulation were compared with ground truth measurement data with promising results.

A 2D metal photonic crystal structure with a rectangular lattice is designed for directed wave propagation in the microwave frequency band. The dispersion curve of EPC is computed for designing the directed period array.In order to favor the computing ,the rectangular period array is studied,which is differenr from the refrerence that is designed in optical range and uses the dielectric rods and hexagonal structure to compose the period array. The computed dispersion curves are combined with the theory of finite thick period array for obtainning the directed wave propagation structure. The influence of the number of metal rods on the antenna directionality is investigated, and the simulation results are compared and analyzed. It is found that when the number of transverse metal rods increases, the directionality of the antenna is enhanced, and the radiant power of the sidelobe radiation can be reduced. Based on the simulation results, the actual 2D metal photonic crystal array is constructed for the measurement validation.According to measurement results, the antenna located in the center of the array can get good directionality at 3.1 GHz.

In this paper, a wideband differential phase shifter based on modified T- and Pi- networks is proposed. Invoking the even-odd mode analysis in this symmetric phase shifter, closed-form equations of its S-parameters are derived. The derived equations enable a generic design scheme of the phase shifter, that is, ideally the phase shifter can be designed for any differential phase requirements. To illustrate the proposed idea, design parameters for differential phases of 45˚, 60˚, 75˚, 90˚, 105˚ and 120˚ are evaluated and tabulated considering a center frequency of 3 GHz. Simulation of these examples using the Keysight ADS exhibits the intended performance. For validation, a 90˚ phase shifter has been fabricated and tested. The measurement results show a return loss better that 10 dB, an insertion loss of less than 1 dB, and a ± 7° of phase deviation from 1.18 GHz to 5.44 GHz, which is equivalent to a fractional bandwidth of 142%.

Knowledge of peat depth distribution is vitally important for accurately estimating carbon stock within tropical peatlands. These estimates aid in understanding the role of tropical peatlands in global environmental change processes. This study evaluates the potential of C-band dual-polarization synthetic aperture radar (SAR) data for peat depth classification on oil palm plantations in Siak Regency, Riau Province, Indonesia. Specifically, features derived after the ground-range radar cross section (sigma-naught or sigma⁰) and slant-range perpendicular radar cross section (gamma-naught or γ⁰) for both polarization channels of C-band Sentinel-1 data were compared and evaluated on monthly basis, during 2015, for discriminating peat depth classes using the decision tree classifier. Overall, γ⁰ features yielded a higher value of distance factors (DF) for peat depth classes, for both polarization channels, than those produced by the sigma⁰, indicating a better performance in discriminating peat depth classes. Moreover, the seasonal variation of rainfall intensity was discovered to be influencing feature selection for peat depth classification. Thus, the combination of γ⁰ features derived in the much rain months was selected for separating the shallow- and medium-peat classes, whereas those derived in the less rain months was selected for discriminating the deep- and very deep-peat classes. In addition, the developed methodology gave the best accuracy for the very deep-peat class, with 76% and 67.86%, producer's accuracy (PA) and user's accuracy (UA), respectively, followed by the shallow-peat class that yielded a PA of 64% and UA of 80%. Subsequently, the deep-peat class produced a PA of 58% and UA of 59.18%, whereas the medium-peat class yielded the lowest PA and UA, of 54% and 49.09%, respectively. This study showed that the C-band dual-polarization SAR data have potential for classifying peat depth classes, particularly on oil palm plantations, and might serve as an efficient tool in peat depth classification used for sustainable management of tropical peatlands.

In this work, a new analytical matrix formulation approach for the characterization of a microwave planar structure printed on a complex medium is detailed. The approach is based on the Generalized Exponential Matrix Technique (GEMT) combined with the Method of Moments (MoM)and Galerkin's procedure. The mathematical calculation development is a robust approach that exclusively uses matrix formulations starting from Maxwell's equations until the derivation of a compact form of the Green's tensor of the studied structure. Reduced complexity and calculation simplicity foundation of the applied approach have actually incited the authors to consider the case study of a complex bianisotropic lossy chiral substrate medium. The complexity of the medium is expressed by full tensors form of all four constitutive parameters: permittivity, permeability and magnetoelectric parameters, each is represented by a nine-element tensor. To investigate the electromagnetic behavior of complex media, results of particular bianisotropy cases are presented and discussed. Original results of the biaxial chiral anisotropy case are carried out, discussed and compared with data available in literature.

A mode-matching solution to plane wave scattering by a plasmonic nanohole array consisting of a silver film perforated by an infinite square array of circular holes is presented. A complete orthonormal basis set consisting of waveguide modes satisfying an impedance boundary condition on the hole wall is derived. Impedance boundary conditions are satisfied on the upper and lower horizontal surfaces of the film and on the walls of the hole. Extraordinary optical transmission (EOT) is studied over optical wavelengths. Theory predicts a peak transmission value that is in better agreement with experiment than previous modal studies. The effect of film thickness on coupling between modes bound to the upper and lower surfaces is studied. The transmission profile for thinner films evinces two peaks at different wavelengths resulting from strong coupling between surface waves bound to the upper and lower surfaces. For thicker films, the surface waves decouple and a single peak is observed. The effect of hole radius on EOT is considered. It is demonstrated that transmission peaks occur for holes of a roughly constant electrical size. A relationship between the lattice constant and the transmission-to-area efficiency is quantified.

In binned arrays, radiators are classically located according to a uniform probability distribution. By doing so, it has been shown that they have the same mean radiation pattern as totally random arrays (i.e., the ones for which the radiators' positions are continuous independent and identically distributed random variables defined over the whole array aperture) but a lower variance. In this paper, we introduce a new class of generalised binned arrays by generalising the rule for assigning the radiators' positions. These new binned arrays, while maintaining the aforesaid advantage (in terms of the variance behaviour), allow to set the mean radiation pattern according to some design requirements. The achievable performance is estimated by measuring how much the radiation pattern deviates from the desired mean radiation pattern by resorting to the up-crossing theory. In particular, the study is developed for the case of symmetric arrays, which allows for easier maths. The paper includes an extensive numerical analysis which allows to check the developed theory. In particular, it focuses on the comparison between the generalised binned array and the totally random ones. A comparison with the nonuniform arrays coming from the density tapering approach is also presented. The latter appears natural in view of the new bins selection rule, which, as will be shown, is a sort of density-tapering in which the role of the reference current is played by the radiators' position density distribution.

In this letter, a two-element wide-band patch antenna array with low cross-polarization is presented. The patch is excited by a magnetic-coupled loop. The two elements are placed symmetrically about the center of the array. Compared to the conventional feeding structure, the proposed feeding structure has the advantages of simple structure and much lower cross polarization. Parametric studies show the usefulness of the proposed feeding structure. Prototypes for the element and array have been fabricated and tested. The antenna array can achieve an impedance of 29.1% for VSWR <2 and a stable gain around 11.2 dBi. Unidirectional radiation patterns with low cross polarization less than -18 dB within the 3-dB beamwidths are obtained. The height of antenna is about 0.12λ(where λ is the free-space wavelength referring to the center frequency of the working band). Moreover, the proposed antenna is dc grounded, which is suitable for outdoor base station applications.

In this paper, a novel configuration for linearly polarised Dual Frequency Microstrip Antenna at S- and X-bands is presented. The proposed configuration utilises the frequency ratio of 1:3.3 between the two bands to its advantage by saving space. It uses the antenna at S-band as ground plane for a 2 x 2 antenna array at X-band without any additional requirement of separate space and ground plane. The patches are electromagnetically coupled to give measured bandwidth (|S11| <-10 dB) of 13% at S-band and 6.2% at X-band. It gives isolation better than 38 dB over the entire bandwidth of the two frequency bands. The measured antenna gain is 7.5 dB at S-band and 10.5 dB at X-band.

Recently, a new analytically regularizing procedure, based on Helmholtz decomposition and Galerkin method, has been proposed to analyze the electromagnetic scattering from a zero-thickness perfectly electrically conducting disk. The convergence of the discretization scheme is guaranteed and of exponential type, i.e., few expansion functions are needed to achieve highly accurate solutions. However, it leads to the numerical evaluation of improper integrals of asymptotically oscillating and slowly decaying functions. Asymptotic acceleration techniques allow to obtain faster decaying integrands without overcoming the problem of the oscillating nature of the integrands themselves, i.e., the convergence of the integrals becomes slower and slower as the accuracy required for the solution is higher. In this paper, by means of algebraic manipulations and a suitable integration procedure in the complex plane, an alternative expression for the scattering matrix coefficients involving only fast converging proper integrals is devised. As shown in the numerical results section, the proposed technique is very effective and drastically outperforms the classical analytical asymptotic acceleration technique.

This paper presents the principle and design of an experimental bench of an oversaturated superconducting machine with radial flux density. A designed experimental bench is under construction to validate the computation principle of the inductor. Also, this work describes the encountered problems and lays out the tools that permit to study a high power oversaturated superconducting machine.

The primary objective of this paper is to design a high-gain, circularly polarized patch antenna suitable for Radio Frequency Identication (RFID) readers that operate in the FCC and ETSI bands (865-928 MHz). These designs will be used in a healthcare application to provide tag identification for thousands of medicines stored on shelves inside a pharmaceutical warehouse. Consequently, it is important that these antennas provide sucient electromagnetic coverage and polarization diversity in order to boost tag readability and minimize item identification errors. The proposed RFID reader antenna design begins with a single patch with truncated corners on air substrate in order to help us understand the effect of various geometrical parameters on critical antenna figures of merit. A stub is introduced in order to improve the impedance matching characteristics of the antenna. The wideband characteristic of the design, for both impedance matching and axial ratio, is achieved by a second truncated-corner patch antenna positioned on top of the first one. An optimum design is achieved by changing the heights of the main and parasitic patches, the size of the truncated corners, and the probe position. The final antenna designs are verified by comparing measurement and simulation results.

An antenna designated mainly for cellular telephony purposesis presented. It coversone full band from 690 MHz to 2700 MHzwith 6 dB return-loss criterion. The antenna is dimensioned 45 mm by 22.5 mm and is 0.8 mm in thickness. It is composed of a T-shaped monopole on the front-side and a meandered line on the back-side of an FR4 substrate. The T-shaped monopole is responsible for the high-band resonances. The meandered line is divided into three parts: the first partfunctions as a distributed inductor; the second part plays the role as a low-band resonator, and the third part is a tuning element. The distributed inductor and the low-band resonator are both folded strips in configuration, but with different spacing. The tuning element is used to improve the match so that one full band operation can be realized. To clarify the operational mechanism, modesseparately generated from each part are analyzed and compared to modes of the proposed antenna.

Three bent waveguides are proposed and investigated, two for circular waveguide TM₀₁ mode transmission and one for coaxial TEM mode transimission. For high power-handling capacity, all of them are over-mode waveguides. In the bend, circular or coaxial waveguides transmitting only sector waveguide TE₁₁ modes are split into several same sector waveguides by metal plates and metal rod. Those sector waveguides are grouped by their lengths. Different lengths of sector waveguides mean there are phase differences of the TE₁₁ modes after bending. Due to requirements of mode conversion, the phase difference regulated by radii of circular waveguide and metal rod must be 2nπ, n = 0, 1, 2…. Since the phase difference is independent of bend radius, the radius could be as small as possible. One of the prototypes is experimented, and the test result of the VSWR shows that simulation has good match with experiment. Insertion loss is 0.2 dB at 8.4 GHz, which proves the feasibility of the prototype.

A wideband interdigital capacitor (WIDC) is proposed and verified. By short interconnecting the open ends of interval fingers with microstrip lines etched on PCB bottom layer, the spurious spikes that limit the bandwidth of conventional interdigital capacitor (IDC) are eliminated. The bandwidth and capacitance of IDC increase more than 2800% and 100%, respectively.

In this paper, we propose a direction-of-arrival (DOA) estimation algorithm under unknown mutual coupling with a sparselinear array (SLA). We employ an SLA composed of two uniform linear arrays (ULA), and the element spacing of one of the subarrays is large enough to neglect the effect of the mutual coupling (MC). The forth-order-cumulants (FOCs) of the received data from partial elements of the first subarray and all elements of the second subarrayare exploitedto construct an extended FOC matrix. Then, the DOAs of incident signals are estimated by dealing with the FOC matrix. The array aperture is extended greatly due to the sparsestructure. Hence, the proposed method shows much better performance than some classical blind DOA estimation methods in accuracy and resolution. We also proposed some simulation results to prove the effectiveness of our method.

In this paper, a microstrip lowpass filter with -3 dB cutoff frequency of 3.8 GHz consisting of two cascaded resonators with flabelliform patches and two symmetric suppressing cells is proposed. To design the filter, the impact of each transmission line on the frequency response is determined by extracting the equations of the insertion loss (S21) and return loss (S11) on the basis of the equivalent LC circuit of the main resonance cell and the cascaded structure. The designed filter is constructed and tested, and a good agreement between the results of simulation and measurement is obtained. In the whole stopband region, a return loss close to zero and an acceptable suppression level of -30 dB from 4.47 to 25.17 GHz are achieved. Furthermore, a flat insertion loss in the passband and a low return loss (-23.02 dB) in the stopband can prove desired in-band and out-band frequency response.

In the field of radar target detection, vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has drawn great attention in recent years because of its prospect to improve the capacity of information acquisition. As a typical vortex EM wave, the high-order Bessel vortex beam (HOBVB) has the properties of non-diffraction propagation, small central spot diameter, good direction, and long propagation distance. This study investigates the scattering of non-diffracting HOBVB by radar targets. The mathematical description of the electromagnetic field components of the arbitrarily incident HOBVB are given. The surface integral equations for solving the scattering problems involving typical radar targets are established. The effects by OAM intrinsic mode characteristics on the radar scattering cross section are simulated. This investigation is expected to provide useful guidance for revealing EM scattering mechanism in the OAM domain.

In this paper, a horizontally polarized (HP) omnidirectional antenna array with a broadband characteristic is presented. The proposed antenna consists of a circular array based on four planar arc dual-dipole structures, a wideband 1-to-4 feeding network with baluns, four reflectors and twelve directors. The arc dual-dipoles with four etched slots are introduced to obtain the broadband characteristic. By using twelve directors in front of the dipoles, the gain variation in the horizontal plane is improved. In addition, the reflector elements are able to improve the gain for the middle frequency band. With the concept, a prototype antenna with an overall size of 0.66λ_L × 0.66λ_L × 0.01λ_L (λ_L× is the free-space wavelength at the lowest frequency) is fabricated and measured. The designed antenna exhibits a relative impedance bandwidth of 98.3% (1.245-3.652 GHz) for |S₁₁|<-10 dB. The HP omnidirectional patterns provide a gain variation less than 3.0 dB over the frequency band 1.245-3.519 GHz (95.5%). Within the impedance bandwidth, the cross-polarization level is lower than -20 dB in the horizontal plane.