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[IEEE 2018 IEEE MTT-S International Microwave and RF Conference (IMaRC) - Kolkata, India (2018.11.28-2018.11.30)] 2018 IEEE MTT-S International Microwave and RF Conference (IMaRC) - 3D Frequency Selective Surfaces based on Substrate Integrated Waveguide Technology
摘要： In this paper, a novel design technique for designing 3D frequency selective surfaces (FSS) is proposed based on substrate integrated waveguide (SIW) cavity technology. The proposed design comprises of two tightly coupled FSS elements through the series of periodically spaced metallic vias which are separated a by a finite gap. The structure exhibits passbands characteristics with a relative bandwidth of 14.14%. Further, it exhibits two sharp roll-off performance characteristics on either edges of transmission frequency with two transmission zeros. The parametric study has been conducted to analyze its effect on frequency response of the structure. Furthermore, the material characteristics are derived to analyze the material behavior of the structure.
关键词： 3D FSS,Substrate integrated waveguide,Electromagnetic materials,reflection coefficient,transmission coefficient,EM wave propagation,Frequency selective surface (FSS)
更新于2025-09-12 10:27:22
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Longitudinal wave propagation in a one-dimensional quasi-periodic waveguide
摘要： The paper deals with the analysis of wave propagation in a general one-dimensional (1D) non-uniform waveguide featuring multiple modulations of parameters with different, arbitrarily related, spatial periods. The considered quasi-periodic waveguide, in particular, can be viewed as a model of pure periodic structures with imperfections. Effects of such imperfections on the waveguide frequency bandgaps are revealed and described by means of the method of varying amplitudes and the method of direct separation of motions. It is shown that imperfections cannot considerably degrade wave attenuation properties of 1D periodic structures, e.g. reduce widths of their frequency bandgaps. Attenuation levels and frequency bandgaps featured by the quasi-periodic waveguide are studied without imposing any restrictions on the periods of the modulations, e.g. for their ratio to be rational. For the waveguide featuring relatively small modulations with periods that are not close to each other, each of the frequency bandgaps, to the leading order of smallness, is controlled only by one of the modulations. It is shown that introducing additional spatial modulations to a pure periodic structure can enhance its wave attenuation properties, e.g. a relatively low-frequency bandgap can be induced providing vibration attenuation in frequency ranges where damping is less effective.
关键词： frequency bandgaps,quasi-periodic structures,elastic wave propagation,imperfections,dispersion relation,method of varying amplitudes
更新于2025-09-12 10:27:22
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-point dependent electromagnetic beam propagation in a graphenelike triangular metallic photonic structure
摘要： We study the electromagnetic wave propagation in a graphenelike triangular metallic photonic structure and show that, associated to trigonally warped Dirac cones, the transport properties resulting from an incident beam at the armchair edge display drastically different behaviors as compared to the results obtained for other analogous systems. Namely, at K point, only the center beam associated to the lower Dirac cone and the side beams to the upper cone and, at K (cid:2) point, only the center beam associated to the lower cone display signi?cant intensities. The other expected beams are all strongly inhibited. This can be related to the metallic nature of the structure, where the low frequency electromagnetic bands are formed by local resonance modes con?ned inside the structural units. A propagating wave should follow the structure local patterns that govern its ?eld distribution, whose symmetry properties determine its excitation by an incident wave.
关键词： graphenelike triangular metallic photonic structure,trigonal warping,armchair edge,electromagnetic wave propagation,Dirac cones
更新于2025-09-12 10:27:22
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Fiber Optic and Atmospheric Optical Communication || Optical Wave Propagation
摘要： Electromagnetic (EM) wave plays a key role in modern communication systems, radio and optical, including optical telecommunication systems. Therefore, fiber optic or laser communications emphasize the EM phenomena described mathematically by Maxwell’s unified theory, which we will consider in detail subsequently. Investigation of optical communications started just after the invention of the laser in 1960. Atmospheric propagation of optical waves was investigated parallelly with improvements in optical lasers and understanding of the problems of optical wave’s generation both in the time and space domains. Thus, problems with weather, line-of-site (LOS) clearance, beam spreading and bending in the real atmosphere consisting of gaseous structures (aerosols, fog, smoke, turbulence, etc.), and hydrometeors (snow, rain, clouds, etc.) eliminated free-space optical communication as a major aspect in wireless communication.
关键词： Optical Wave Propagation,Maxwell’s Equations,Atmospheric Propagation,Electromagnetic Waves,Fiber Optic Communication
更新于2025-09-11 14:15:04
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Longitudinal wave propagation in one-dimensional waveguides with sinusoidally varying depth
摘要： In this paper, longitudinal elastic wave propagation in one-dimensional waveguides with sinusoidally varying depth is investigated. Furthermore, different types of such waveguide designs are explored to understand their capability to attenuate the group speeds as well as the velocity amplitudes. The plane waveguide con?gurations with sinusoidally varying depth, of three types, namely Convex, Concave and Full, along with their combinations and variants, whose segmental depth along the length of the waveguide is modeled by a sine function having an amplitude parameter ?? and the half-period p, which leads to a governing differential equation with variable coe?cients, are considered in this study. To study the longitudinal wave propagation in these inhomogenous waveguides, a novel superconvergent ?nite element formulation is developed, which gives an exact stiffness matrix. In addition to the wave propagation analysis, static and free vibration behaviors in these waveguides are also studied. The implemented superconvergent ?nite element formulation for these studies is validated with the commercial ?nite element software Abaqus. In the ?rst part of the wave propagation analysis, abilities of the three plane waveguide con?gurations with sinusoidally varying depth to attenuate high amplitude and frequency waves are investigated for different values of ??. Next, four different waveguides composed of Convex-Concave combinations are studied with an aim to get better attenuation. Following this, the waveguides’ segmental parameters, ?? and p, are varied across the segments along the length of the waveguide, using a sine function and polynomial power law to see if such graded variations give better energy absorption properties compared to the plane waveguides whose parameters are unvarying. In the last part, a developed inhomogenous rod of a certain length is inserted in the middle of a uniform waveguide to study the possibility of changing the longitudinal wave propagation characteristics of the uniform waveguide. The results from the analyses show that the group speed and amplitude of the longitudinal wave in these con?gurations change signi?cantly with space as well as with frequencies, especially for high values of ??. The Concave and Full waveguides delay the propagation of longitudinal waves signi?cantly, which translates into the re?ected waves appearing later in the chosen large time window. The Convex waveguide and its variants reduce the wave amplitudes signi?cantly. Building on these results, some waveguides with notable attenuation characteristics are proposed.
关键词： Sinusoidal depth variation,Superconvergent ?nite element,Convex waveguide,Inhomogenous waveguide,Longitudinal wave propagation,Dispersive waves
更新于2025-09-11 14:15:04
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Design and implementation of 2.5D frequency-selective surface based on substrate-integrated waveguide technology
摘要： In this paper, the patch-type frequency selective surfaces (FSS) based on substrate-integrated waveguide (SIW) technology is proposed to improve the bandwidth (BW) and angular performance. The proposed FSS configuration overcomes the limitations of both conventional 2D and 3D FSS structures. A closely coupled cascaded mechanism is employed to combine two identical FSS elements separated by thin dielectric substrate results in incorporation of SIW technology; hence, named as 2.5D FSS. A derived equivalent circuit model is used to estimate the basic performance of proposed FSS–SIW elements, and the response of analytical expressions has been validated and final design is obtained using full-wave simulations. Two basic FSS elements viz. single square loop and a Jerusalem cross have been investigated to prove the enhancement in their BW and angular stability. The proposed technique evidently improves the BW and angular stability of FSS structures than in its established form. Besides, various important parameters that influence the performance characteristics of reported 2.5D FSSs are also studied. The important observations made on the thickness, as the thickness increases the bandstop FSS, can change to bandpass FSS. Finally, the proposed FSS structure has been fabricated and measured using free space measurement setup, to show the effectiveness of theoretical results. The measured results show good agreement with simulated results at normal and oblique incidence angle.
关键词： modeling and measurements,microwave measurements,EM field theory and numerical techniques,wave propagation and scattering
更新于2025-09-11 14:15:04
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Time-domain Formulation of a Multi-layer Plane Circuit Coupled with Lumped-parameter Circuits using Maxwell Equations
摘要： We calculate electromagnetic phenomena in the multi-layer plane circuit starting from the Maxwell equations. We present a numerical method of potential and current density in two-dimensional conductors, where their time developments are treated as phenomena of wave propagation. We treat the plane conductors by dividing them into small finite-volume elements, similar to the case of the partial element equivalent circuit method, and the transport equations are then solved by the finite-difference time-domain method. Furthermore, we develop a calculation method for the boundary in a multi-layer plane by applying the method we have used in multi-transmission lines. We formulate the boundary conditions of a multi-layer plane coupled with lumped-parameter circuits and introduce an algorithm to reduce calculation costs that are largely associated with the two-dimensional extension from the multi-transmission-line case. We perform calculations of the wave propagation of potential, current density, and charge density in the time domain for a simple plane circuit. these calculations are presented as supplementary materials of the present paper.
关键词： wave propagation,multi-layer plane circuit,electromagnetic phenomena,lumped-parameter circuits,potential and current density,numerical method,finite-difference time-domain method,Maxwell equations
更新于2025-09-11 14:15:04
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Analysis of Electromagnetic Wave Propagation in Variable Magnetized Plasma via Polynomial Chaos Expansion
摘要： A three-dimensional stochastic FDTD algorithm is developed and applied to electromagnetic wave propagation in collisional magnetized plasma characterized by a variable electron density, collision frequency, and background magnetic ?eld. The proposed stochastic model is based on the expansion of the random / variable time-domain electric and magnetic ?elds in terms of orthogonal polynomials in independent random variables representative of the variable ionospheric content. Electromagnetic wave propagation in magnetized plasma having low variability (small deviations) and also high variability (large deviations) of the electron density, collision frequency, and background magnetic ?eld is studied. The stochastic algorithm is validated against brute-force Monte Carlo results. The algorithm is considerably more computationally ef?cient than Monte Carlo. When applied to electromagnetic wave propagation in the ionosphere, the variability of the Earth’s magnetic ?eld and ionospheric parameters can be accounted for due to naturally varying space weather conditions and day-to-day variations, measurement errors, etc. Although only electrons are considered here, positive and negative ions may be accommodated in a straight-forward manner.
关键词： ?nite-difference time-domain (FDTD),electromagnetic wave propagation,ionosphere,polynomial chaos,uncertainty,collisional magnetized cold plasma
更新于2025-09-11 14:15:04
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Atmospheric Effects on Millimeter and Sub-millimeter (THz) Satellite Communication Paths
摘要： Satellite communications require more bandwidth due to the necessity of increasing the capacity of communication channels and bandwidth to end-users. As a result, looking for new bands is required in the electromagnetic spectrum including millimeter and sub-millimeter wavelengths. Recent technological developments made the extremely high frequencies (EHF) above 30 GHz as a candidate for wireless applications such as the fifth generation (5G) of mobile communications, high resolution radars, and remote sensing. The EHF communication systems are becoming more and more commercial, cheap, and compact. However, the fact that the atmospheric medium is not completely transparent to millimeter waves requires considerations of the frequency selective absorption and dispersion effects emerging in this band. These phenomena affect also remote sensing in the millimeter and sub-millimeter waves (the terahertz frequencies). The atmospheric effects on the propagation of millimeter and sub-millimeter wave transmission from land to satellite are discussed. It is shown that not only atmospheric absorption plays a significant role on the received signal strength but also the refraction index of the atmospheric medium. The inhomogeneous refractivity causes the beam to Bbend^ along the propagation path, and it may even Bmiss^ its destination. This phenomenon should be considered in the design of a link operating in extremely high frequencies involving highly directive antennas.
关键词： Millimeter wave propagation,Terahertz waves,Millimeter wave satellite communications
更新于2025-09-10 09:29:36
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Elasto-electric coupling for direct electric field distribution measurement in semiconductor structures
摘要： Semiconductor materials are widely used in electronic industry, but their electrical characterization remains complex to estimate without a good model. It has already been shown that an elasto-electric coupling can be used to directly and non-destructively probe the electrical properties at the external interfaces of semi-conductor structures. In this paper, it is shown that such a coupling can also be used to probe the inner interfaces of semi-conductor structures. This capability is demonstrated by using a specific semi-conductor structure including a buried silicon p-n junction 720 lm away from the external electrodes. The signal generated by the elasto-electric coupling clearly shows separately the electric field at the electrodes and at the buried junction. The contact potential at the buried junction estimated from the measurements is in accordance with the semiconductor doping. This makes it possible to use an elasto-electric coupling for the complete characterization of semiconductor structures.
关键词： Pressure-Wave-Propagation method,elasto-electric coupling,semiconductor structures,p-n junction,electric field distribution
更新于2025-09-10 09:29:36