In this paper, a new kind of capsule endoscopy with through-body radar is utilized for the first time. Finite difference time domain (FDTD) method is used to establish an electromagnetic simulation model of stomach. A technique based on the combination of improved back-projection (BP) algorithm and support vector machine (SVM) is proposed to solve the problems of rapidly recognizing tumor shapes in the stomach. In this technique, imaging data can be obtained using the improved BP algorithm and are classified by the SVM. The algorithm must consider the influence of various tissues in the human body: the attenuation of the signal strength of electromagnetic waves, the decrease in speed and the refraction due to the different permittivity between the different organs of the body. These factors will eventually lead to image offset, and even generate a virtual image. It is effective to refrain the displacement of image with modifying the time element of the imaging algorithm by iteration. Simulation results based on data from the model verify its feasibility and validity. Results further demonstrate that the resolution is extremely high. Tumor shapes, which have different sizes, positions, and quantities, can be reconstructed using this approach. When the data are contaminated by noises, the tumor shape in the stomach can still be suitably predicted, which demonstrates the robustness of the method. Finally, classification accuracy analysis for different sampling distances and sampling intervals shows that the effects of changing the distance and intervals on shape recognition are limited. The classification accuracy can also be improved by decreasing the sampling intervals or increasing the sampling distance.

In this paper, a metamaterial loaded square-shaped fractal antenna with two iterations is presented and discussed. A metamaterial loading consistsof split ring resonators (SRRs) which enhances the bandwidth of the antenna keeping the dimensions and size of the antenna same. The square-shaped fractal antenna, which is in the form of three concentric rings, was simulated and fabricated, and the results were shown and discussed. The antenna resonates at three distinct frequency bands 4.3719 GHz, 7.7437 GHz and 10.6374 GHz with the gains of 1.1974 dB, 4.2745 dB and 4.7233 dB, respectively for resonant frequencies. The bandwidths for the antenna are 185 MHz, 198 MHz and 386 MHz for distinct resonant frequencies. The antenna is fabricated using an FR-4 substrate, and the measured resonant frequencies are 4.08 GHz, 7.545 GHz and 10.24 GHz. In metamaterial loading condition, the dimension of the antenna resonates at 4.0105 GHz, 6.8474 GHz and 8.0632 GHz with bandwidths of 636 MHz, 347 MHz and 1.33 GHz at resonant frequencies. The appreciable bandwidth is achieved in such a small antenna without changing dimensions and size of the antenna. The simulated, experimental results and comparison are also presented in this paper.The results show that the proposed method can be used to design high bandwidth and compact fractal microstrip patch antennas without increasing dimensions.

This paper describes a compact triple-band monopole antenna based on metamaterial inspired Open Complementary Split Ring Resonators (OCSRRs) for Wireless Local Area Network (WLAN) and Worldwide interoperability Microwave Access (WiMAX) applications. The monopole antenna with engraved ground plane is used to cover WLAN frequencies (2.67 GHz and 5.47 GHz). The resonant frequency of WiMAX (3.43 GHz) is achieved by introducing metamaterial inspired OCSRR in the monopole antenna. To realize good impedance matching, one more OCSRR is introduced in the monopole antenna. This paper includes the pass band characteristics of OCSRRs as well as negative permittivity details. The prototype antenna is fabricated on an FR-4 substrate having dimension of 29.4 × 26 × 1.6 mm³. Simulated and measured results are shown in good equivalence. The dipole radiation pattern is obtained in the elevation plane (E-Plane), and omnidirectional radiation pattern is obtained in the azimuthal plane (H-Plane). Parametric analysis of OCSRRs is studied to attain the best results. The proposed antenna has adequate advantages, including compact size, multiband, and impedance matching.

This work tries to design an Eddy current braking system that can brake at a very high speed within a short time or a short distance. In order to maximize the braking force and reduce lateral forces that can cause track deformation or damage, a double-sided linear permanent magnet Halbach array is proposed in this paper. Two possible designs (Type I and Type II) have been investigated. By using mathematic models, Finite Element Method (FEM) and experimental results, Type I design of a double-sided linear permanent magnet Halbach array is selected. Compared with the other design, Type I design can provide a much larger braking force. Moreover, the analysis also shows that the mathematic models can well capture the characteristic of Type I design. Thus these models are used to design a set of optimal design parameters such as the length and thickness of permanent magnet block to maximize flux density and braking force per unit mass of permanent magnets. The optimal performance is validated by using FEM.

This paper presents the comprehensive analytical design and numerical performance evaluation of novel millimetrewave (mm-wave) switched-beam networks, based on the Rotman lens (RL) array feeding concept. These passive array devices have been designed for operation in the 28-GHz frequency band, covering the whole 18-38 GHz frequency range. The primary objective of the work is to conduct a thorough feasibility study of designing wideband mm-wave beamformers based on liquid-crystal polymer (LCP) substrates, to be potentially employed as low-cost and high-performance subsystems for the advanced transceiver units and large-scale antennas. The presented RLs exhibit significant output behaviours for electronic beam steering, in terms of the scattering (S) parameters, phase characteristics, and surface current distributions, as the feeding systems' primary functionality indicators.

A hexagonal fractal antenna is presented for satellite navigation applications in this paper. The geometry of the antenna is inspired by the Sierpinski carpet and has compact dimensions, improved bandwidth, good radiation pattern due to the self-similar property of fractal geometry. The bandwidth ranging from 1.54 GHz to 1.61 GHz can work at L1 band of GPS and B1 band of Beidou satellite navigation system. The simulated and measured gains show a good agreement over the bandwidth.

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.