Trapped Surface Wave Research Articles

Curved channels with constant cross sections may support trapped surface waves

Curved channels with constant cross sections are constructed which support a trapped surface wave. Since corresponding eigenvalues are embedded in the continuous spectrum of the water wave problem and therefore possess the natural instability, the construction procedure requires “fine-tuning” of several parameters in the (small) curvature of the channel as well as geometrical restrictions on the cross section. In particular, the mirror symmetry of the cross section with respect to the vertical axis disrupts the procedure, but examples of suitable non-symmetric cross sections are provided.

Complex Mode Dispersion Characteristics of Dielectric Loaded Radially Thick Helix

In this article, a generalized analytical and computational numerical theory, for both the guided and leaky modes, has been developed to investigate the dispersive behavior of dielectric-loaded radially thick helix (DLRTH). The complex root finding Muller iterative algorithm is used to compute the normalized phase and attenuation constants. A unique way has been adopted for the classification of HE and EH hybrid modes present in the proposed structure, and based on that, for the first time, we report that this structure shows physical leaky and trapped surface wave propagation characteristics. Furthermore, in the guided mode, it is seen that both slow wave (SW) and backward wave (BW) exist due to the inherently skewed boundary of the helical geometry. The parametric study of helix radius and pitch angle as well as dielectric constant gives optimized parameter values, which help in designing the proposed structure in the desired mode and at the desired frequencies. Moreover, it is reported that pitch angle aids in controlling and figuring out the leaky mode bandwidth. The analytical cum numerical MATLAB results are successfully verified using CST Microwave Studio computational analysis and are found to be in good agreement. The improved characteristic equations for guided mode find practical applications in the design and performance evaluation of the SW structure (SWS) for the phase delay applications. The leaky mode will find application for beam scanning helical antennas.

Excitation of Airborne Acoustic Surface Modes Driven by a Turbulent Flow

This experiment demonstrates the generation of trapped acoustic surface waves excited by a turbulent flow source through the coupling of pressure fluctuations at the interface between an acoustic metamaterial and a flow environment. The turbulent flow, which behaves as a stochastic pressure source, was interfaced with an acoustic metasurface waveguide stationed in a quiescent environment via a single Kevlar-covered cavity, which ensured no significant disturbance to the flow. The metasurface waveguide produced an acoustic surface mode through evanescent diffractive coupling of the pressure field. This acoustic mode was trapped at the quiescent surface, with its mode dispersion determined by the surface geometry. The results of two different metasurface geometries are discussed: 1) a slotted cavity array, and 2) a meander connected cavity array, with each demonstrating a different trapped surface wave characteristic. Fourier transform and correlation analyses of spatially resolved temporal acoustic signals, measured close to the metamaterial surface, were used to construct the frequency- and wavevector-dependent acoustic mode dispersion. The results demonstrate that the flow can be used to excite acoustic surface modes and that their mode dispersion may be tailored toward realizing novel control of turbulent flow through acoustic-flow interactions.

Approximate Transient Field for a Gaussian Pulse Generated by a Horizontal Electric Dipole in a Three-Layered Thin Anisotropic Medium

This letter aims to address the calculation of transient field associated with a horizontal electric dipole (HED) excited by a Gaussian pulse in a three-layered anisotropic medium. Approximate formulas applicable to the far transient fields are derived, and analyzed for the case of a thin dielectric layer (a dielectric slab). The resultant analytical formulas have the merit of offering unique insights about the characteristics of the transient field that includes lateral waves, and trapped surface waves. Furthermore, the transient field is further examined for its propagation characteristics, propagation distance, as well as its dependency on dielectric parameters. Finally, usefulness of the proposed formulas are demonstrated by using a microstrip antenna as an example.

Surface waves in a channel with thin tunnels and wells at the bottom: Non-reflecting underwater topography

We consider the propagation of surface water waves in a straight planar channel perturbed at the bottom by several thin curved tunnels and wells. We propose a method to construct non reflecting underwater topographies of this type at an arbitrary prescribed wave number. To proceed, we compute asymptotic expansions of the diffraction solutions with respect to the small parameter of the geometry taking into account the existence of boundary layer phenomena. We establish error estimates to validate the expansions using advances techniques of weighted spaces with detached asymptotics. In the process, we show the absence of trapped surface waves for perturbations small enough. This analysis furnishes asymptotic formulas for the scattering matrix and we use them to determine underwater topographies which are non-reflecting. Theoretical and numerical examples are given.

Electromagnetic fields of a horizontal infinitely long wire buried in three-layered medium

ABSTRACTIn this paper, the electromagnetic fields of a horizontal infinitely long wire source buried in a three-layered medium are studied. The source and the observation points are located in the middle region. The expressions of the electromagnetic waves are more complex because of the multiple reflections from the up and down boundaries. The electromagnetic field components between the two boundaries are given, and the trapped surface waves and lateral waves along the two boundaries are computed. The analysis and computations have some practical applications in the line sources buried in the earth or cements.

Radiation patterns of a horizontal electric dipole in a four-layered region and applications for microstrip antennas

ABSTRACTThe present work focuses on the radiation field excited by a horizontal electric dipole (HED) in a four-layered region composed of a perfect conductor covered with two dielectrics and the air above. Analytical expressions for the radiation field are derived for the case of both the source and the observation point being on or near the air-dielectric boundary. The propagation characteristics of the interference phenomenon are investigated. The radiation field components undergo sharp interference as the relative permittivities and dielectric layer thicknesses increase. When the observation angle , the trapped surface wave predominates in the total field. Otherwise, the total field is determined primarily by the lateral wave. Due to the useful applications for microstrip antennas, radiation patterns of a patch antenna with specific current distributions are investigated. Some special cases of interest are discussed. The proposed formulas offer the potential to develop planar four-layered circuit structures.

Evaluation of the Trapped Surface Wave of a Vertical Electric Dipole Based on Undetermined Coefficient Method in the Presence of N-Layered Region: A Graphical Approach

In previous studies, the trapped surface wave, which is defined by the residue sums, has been addressed in the evaluation of the Sommerfeld integrals describing electromagnetic field of a vertical dipole in the presence of three-layered or four-layered region. But unfortunately, the existing computational scheme cannot provide analytical solution of the field in the presence of the N-layered region when N > 4. The scope of this paper is to overcome the limitations in root finding algorithm implied by the previous approach and provide solution of poles in stratified media. A set of pole equations following with explicit expressions are derived based on the undetermined coefficient method, which enable a graphical approach to obtain initial values of real roots. Accordingly, the generated trapped surface wave components are computed when both the observation point and the electric dipole source are on or near the surface of a dielectric-coated conductor. Validity, efficiency, and accuracy of the proposed method are illustrated by numerical examples.

Simulation and Experimental Verification for a 52 GHz Wideband Trapped Surface Wave Propagation System

Trapped surface wave (TSW) provides a flexible 2-D wireless solution when compared to existing wired and free space communications systems. This work aims to provide the theoretical guidance, supported by simulation techniques and experimental verifications, for 1) designing the wideband and highly efficient rectangular aperture TSW transducers and 2) selecting the best reactive surface impedance for high efficiency. First, a method for computing the TSW excitation efficiency is proposed for the first time and it can be applied to different kinds of reactive surface geometries and transducer apertures. Then, the relation between the TSW excitation efficiency, surface reactance, and aperture height is derived. Then, the maximum excitation efficiency, the corresponding optimal surface reactance, and aperture height are presented. Furthermore, the relation between the TSW angular coverage and aperture width is determined. These studies show that the aperture height mainly determines the TSW excitation efficiencies, while the aperture width controls the TSW angular coverage; hence, the two aperture parameters of a transducer can be independently determined. Finally, an experiment setup, based on the provided guidelines, has been built to demonstrate a 52 GHz wide 3 dB-transmission-bandwidth for high-performance communications systems.

Rancang Bangun Antena Helix Mode Axial dan Patch Meanderline DGS untuk Aplikasi LPWAN Berbasis IoT pada Daerah Rural

Low Power Wide Area Networks (LPWAN) applications are a major concern in infrastructure. Rural are areas that have a poor quality signal; the cause lies in the location of the rural regions away from the coverage area Base Transceiver Station (BTS) so that the need for telecommunications equipment in the form of Global System for Mobile communications (GSM) repeaters. GSM repeater devices require an antenna that has a large gain mainly on the receiving antenna, one antenna that has a large gain character is helix axial mode has a large dimension resembling a spring and has a directional radiation pattern properties, whereas the antenna with an omnidirectional radiation pattern is a patch meander line antenna has compact dimensions and is easy to fabricate. The meanderline patch antenna has the disadvantage one of which is the small gain caused by trapped surface waves on the ground. This research will discuss the design and realisation of helix axial mode, and patch meanderline Defected Ground Structure (DGS) for Low Power Wide Area Networks (LPWAN) application in a rural area so it can be used for Internet of Things (IoT) based weather monitoring. Integrating antenna helix axial mode as receiving antenna and antenna patch meanderline DGS as rebroadcast antenna in GSM repeater able to make edge network in a rural area become High-Speed Packet Access + (HSPA +) network. The test result IoT based obtained the value of Received Signal Strength (RSSI) an average of -89 dBm in HSPA+ network.

Dispersion features of complex waves in a graphene-coated semiconductor nanowire

AbstractThe dispersion features of a graphene-coated semiconductor nanowire operating in the terahertz frequency band are consistently studied in the framework of a special theory of complex waves. Detailed classification of the waveguide modes was carried out based on the analysis of characteristics of the phase and attenuation constants obtained from the complex roots of characteristic equation. With such a treatment, the waves are attributed to the group of either “proper” or “improper” waves, wherein their type is determined as the trapped surface waves, fast and slow leaky waves, and surface plasmons. The dispersion curves of axially symmetric TM0n and TE0n modes, as well as nonsymmetric hybrid EH1n and HE1n modes, were plotted and analyzed in detail, and both radiative regime of leaky waves and guided regime of trapped surface waves are identified. The peculiarities of propagation of the TM modes of surface plasmons were revealed. Two subregions of existence of surface plasmons were found out where they appear as propagating and reactive waves. The cutoff conditions for higher-order TM modes of surface plasmons were correctly determined.

A highly accurate analytical solution for the surface fields of a short vertical wire antenna lying on a multilayer ground

A highly accurate analytical solution is derived to the electromagnetic problem of a short vertical wire antenna located on a stratified ground. The derivation consists of three steps. First, the integration path of the integrals describing the fields of the dipole is deformed and wrapped around the pole singularities and the two vertical branch cuts of the integrands located in the upper half of the complex plane. This allows to decompose the radiated field into its three contributions, namely the above-surface ground wave, the lateral wave, and the trapped surface waves. Next, the square root terms responsible for the branch cuts are extracted from the integrands of the branch-cut integrals. Finally, the extracted square roots are replaced with their rational representations according to Newton’s square root algorithm, and residue theorem is applied to give explicit expressions, in series form, for the fields. The rigorous integration procedure and the convergence of square root algorithm ensure that the obtained formulas converge to the exact solution. Numerical simulations are performed to show the validity and robustness of the developed formulation, as well as its advantages in terms of time cost over standard numerical integration procedures.

Electromagnetic Propagation in Four-Layered Media Due to a Vertical Electric Dipole: A Clarification

This communication presents a quasi-analytical method for predicting the electromagnetic propagation in four-layered media due to a vertical electric dipole. The method includes the components known as the direct, ideal reflected, lateral, and trapped surface waves. Previous literature, studying less complex geometries, is extensively reviewed and found to be incomplete and inaccurate in a number of places. These deficiencies are highlighted and the methodology is presented with enough detail to allow repetition of the results. Results are shown which approximate the scenario of a leaking water-pipe, buried in the shallow sub-surface. It is shown that the trapped surface wave does not dominate in this scenario. Furthermore, it is shown that the trapped surface wave magnitude is reduced when conductivity of the fourth layer is reduced, or when the third layer thickness is increased; these results fit the qualitative expectation based on previous results.

P.109: Improvement of the Outcoupling Efficiency of Blue OLEDs

AbstractWe propose a nanostructured blue organic light‐emitting diode (OLED) with a perforated WO3 hole injection layer that improves the outcoupling efficiency of blue OLEDs by the extraction of trapped surface plasmon polaritons and wave guide modes.

Electromagnetic field of a horizontal electric dipole buried in a medium covering one-dimensionally anisotropic medium

The electromagnetic fields of a horizontal electric dipole buried in a medium covering one-dimensionally anisotropic medium are studied. There are three media, one-dimensionally anisotropic medium covered with a dielectric under the air. The electromagnetic field components are complex because of the multiple reflections from the up and down boundaries. The electromagnetic field components between air and one-dimensionally anisotropic medium are given, the trapped surface waves and lateral waves along the dielectric-anisotropic medium boundary are computed. The results have some practical applications in the communication in sea or lake above one-dimensionally anisotropic earth or sediments.

ELECTROMAGNETIC FIELD OF A HORIZONTAL INFINITELY LONG MAGNETIC LINE SOURCE OVER THE EARTH COATED WITH A DIELECTRIC LAYER

In this paper, the electromagnetic fleld of a horizontal inflnitely long magnetic line source over the dielectric-coated earth is treated analytically, and the complete approximate solution for the radiated fleld under the far-fleld conditions is outlined. The total fleld is composed of four modes: the direct wave, the ideal re∞ected wave or image wave, the trapped surface wave, and the lateral wave. In particular, the complete analytical formulas are obtained for both the trapped surface wave and the lateral wave. The trapped surface wave is determined by the sum of residues of the poles. When the inflnitely long magnetic line source or the observation point is away from the planar surface of the dielectric-coated earth, the trapped surface wave decreases exponentially with height, and the total fleld is determined primarily by the lateral wave. When the conductivity of the earth is large, and both the inflnitely long magnetic line source and the observation point are on or close to the air-dielectric boundary, the total fleld is determined primarily by the trapped surface wave.

Electromagnetic Field of a Horizontal Infinitely Long Wire Over the Dielectric-Coated Earth

The simple analytical formula for the electromagnetic field radiated by a horizontal infinitely long wire over the planar surface of the earth coated with a dielectric layer is derived. It is concluded that the total field includes four modes: the direct wave, the ideal reflected wave or image wave, the lateral wave, and the trapped surface wave. In particular, both the trapped surface wave and the lateral wave are examined in detail. From analysis and computations, it is demonstrated the trapped surface wave, which is determined by the sum of residues of the poles, can be excited efficiently. When both the infinitely long wire and the observation point are on or near the planar surface, the trapped surface wave is dominant.

Electromagnetic environment around a high-speed railway using analytical technique

A switched-mode unit used in electric locomotive generates a strong high frequency conducted electromagnetic interference (EMI), which radiates electromagnetic energy through railway lines. Evaluation of magnetic field using analytical technique based on contour integral is presented, in order to assess the electromagnetic environment around a high-speed railway. Actual railway multiconductor finitely long overhead lines are represented by an infinitely long single line above two-layered earth, whose characteristic is different from homogeneous earth. Owing to the constraint of the GB/T 24338-2009 and the high frequency investigated (a few MHz), only the magnetic fields are examined. The magnetic fields consist of four components: the direct wave, the ideal reflected wave or image wave, the trapped surface wave, and the lateral wave. The calculation results proved that due to the presence of the trapped surface wave, the magnetic field of the observer point on the interface is strongly influenced, when the line is on or closed to the interface.

Trapped surface waves in a periodic layer of a heavy liquid

The spectrum of a periodic waveguide with immersed and semi-immersed cylindrical bodies, the axes of which are parallel to the generatrix of the periodic relief of the bottom, is investigaged within the limits of the linearized theory of waves on the surface of a heavy liquid. Simple sufficient conditions for the existence of localized solutions are discovered in the case of a wave travelling at an acute angle to the generatrix. The numerous consequences of the result are discussed and a periodic waveguide is constructed, in the intrinsic spectrum of which there is a lacuna.

A novel approach for detecting trapped surface waves in a canal with periodic underwater topography

A new approach is proposed to detect trapped modes in periodic canals. The obtained sufficient condition is new even for a straight canal with a body piercing the water surface as well. To cite this article: S.A. Nazarov, C. R. Mecanique 337 (2009).