Zenneck Wave Research Articles

Prism coupling to terahertz surface plasmon polaritons

Silicon prisms are used to couple free-space broadband terahertz into surface plasmon polariton (SPP) modes, otherwise known as surface electromagnetic waves (SEW) or Zenneck waves, on to polished metal surfaces. We show that coupling to surface waves occurs via edge-diffraction and hump-coupling and that attenuated total reflection is not an important coupling mechanism. Coupling and decoupling to a broadband, single-cycle SPP pulse is demonstrated with an energy efficiency of approximately 3.5%. Measurements of SPPs through thin plastic films reveal a strong surface sensitivity and suggest new configurations for maximizing THz SPP utility.

Radiation from a traveling‐wave current sheet at the interface between a conventional material and a metamaterial with negative permittivity and permeability

AbstractIn this paper, we present an analysis for the radiation from a traveling‐wave infinitely‐extent sheet of monochromatic electric current that is placed at the interface between a conventional lossless dielectric and a lossless material possessing negative real permittivity and permeability. The field distributions and the direction of the Poynting vectors in both half spaces are discussed, and some physical remarks are provided. A brief note about launching Zenneck waves by a line current along this interface is also mentioned. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 460–463, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10638

Transverse electric and transverse magnetic Green's function for coherent and incoherent propagation over a finitely conducting rough surface

This paper presents wave propagation over a finitely conducting half‐space whose surface is bounded by a rough surface of small RMS height. An electric or magnetic current source is used to excite the rough surface, and the Green's function for transverse electric (TE) and transverse magnetic wave propagation is obtained. The appearance of roughness at the boundary produces both a coherent (mean) and incoherent (fluctuating) field distribution, which is obtained from Dyson's equation and Bethe‐Salpeter's equation, respectively. The coherent Green's function for vertical polarization exhibits similar characteristics to the Sommerfeld dipole problem where the Zenneck wave pole is modified by roughness. The incoherent field generated by rough surfaces is obtained for both vertical and horizontal polarization, and the conventional cross section per unit length of the rough surface is modified to include the effects of surface roughness. For angles near grazing, a low‐grazing‐angle cross section is obtained by evaluating the Bethe‐Salpeter's equation with the Sommerfeld solution. Finally, the coherent and incoherent intensity for the TE rough surface Green's function is obtained and compared to Monte Carlo simulations.

Pole contribution to the field reflected by sand layers

Measurements of the reflection coefficient at oblique incidence and for inhomogeneous waves are presented for layers of sand having a large flow resistivity and different thicknesses. The dependence of the reflection coefficient on the angle of incidence is different for layers of small thickness and semi-infinite layers, due to the influence of a pole which is related to an ordinary guided wave in the first case, and the Zenneck wave in the second case. Simulations indicate that the amplitude of the Zenneck wave can be measured for small source receiver distances, allowing a simple evaluation in situ of the surface impedance. The same method can be used with the ordinary surface wave for thin layers.

BW media—media with negative parameters, capable of supporting backward waves

AbstractBoth isotropic and uniaxially anisotropic media capable of supporting backward waves are reviewed. Such an effect recently has been of great interest, and certain man‐made composite media have been introduced under the names “media with negative refraction factor” or “left‐handed materials,” effective in a certain band of microwaves. Neither of these names appears to be well founded, and “backward‐wave medium” (or BW medium) is suggested instead. It is shown that, at an interface of a regular and a BW medium, Snell's law does not imply a negative refraction factor. However, the refraction is anomalous in the sense that the transmitted plane wave is a backward wave with a Poynting vector and a wave vector pointing in opposite lateral directions. The significance of the Zenneck wave and guided modes in a cylindrical guide made of BW medium is discussed. Finally, the BW property is extended to uniaxially anisotropic media, and its occurrence is studied for different value combinations of its medium parameters. It is shown that a lateral backward wave can arise when a plane wave is transmitted through an interface when one of the four parameters of the uniaxial medium is negative. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 129–133, 2001.

Sommerfeld and Zenneck wave propagation for a finitely conducting one-dimensional rough surface

Starting with Zenneck and Sommerfeld wave propagation over a flat finitely conducting surface has been extensively studied by Wait (see IEEE Antennas Propagat. Mag., vol.40, p.7-24, 1998) and many other authors. We examine propagation over a finitely conducting rough surface, also studied by many people including Feinberg (1944), Bass and Fuks (1979), and Barrick (see Radio Sci., vol.6, p.517-26, and vol.6., p.527-33). This paper extends the multiple scattering theories based on Dyson and Bethe-Salpeter equations and their smoothing approximations. The theory developed here applies to rough surfaces with small root-mean-square (RMS) heights (/spl sigma/<0.1/spl lambda/). We limit ourselves to the one-dimensional (1-D) rough surface with finite conductivity excited by a magnetic line source, which is equivalent to the Sommerfeld dipole problem in two dimensions (x-z plane). With the presence of finite roughness, the total field decomposes into the coherent field and the incoherent field. The coherent (average) field is obtained by using Dyson's equation, a fundamental integral equation based on the modified perturbation method. Once the coherent field has been obtained, we determine the Sommerfeld pole, the effective surface impedance, and the Zenneck wave for rough surfaces of small RMS heights. The coherent field is written in terms of the Fourier transform, which is equivalent to the Sommerfeld integral. Numerical examples of the attenuation function are compared to Monte Carlo simulations and are shown to contrast the flat and rough surface cases. Next, we obtain the general expression for the incoherent mutual coherence functions and scattering cross section for rough conducting surfaces.

Surface waves over bead layers

For thin bead layers saturated by air, a pole of the reflection coefficient related to a trapped mode inside the layer and a surface wave in air is predicted, and detected with the Tamura method [J. Acoust. Soc. Am. 88, 2259 (1990)]. For semi-infinite layers, the Brewster angle is observed with the same method at oblique incidence at 15 kHz. A description of the related Zenneck wave is performed, at high and low frequencies.

Possibility of superluminal behaviors forX-like and Zenneck waves

The possibility of observing superluminal behavior, in phase and group velocities, over distances of several wavelengths is demonstrated at the microwave scale, where we obtained evidence of X-like waves, and is discussed for the radio frequencies (Zenneck waves).

Surface plasmons and Sommerfeld–Zenneck waves on corrugated surfaces:: Application to high- Tc superconductors

We have performed reflection measurements on corrugated YBa 2Cu 3O 7 samples which exhibit below-gap surface plasmons and Sommerfeld–Zenneck waves for temperatures below and above the critical temperature, respectively. We calculated the optical response of corrugated surfaces and in particular the coupling to surface plasmon polaritons and Sommerfeld–Zenneck waves. These calculations are in good agreement with our measurements.

Surface waves on a lossy planar ferrite slab

The parallel-polarized surface waves which propagate on a planar ferrite slab are considered. The ferrite material is isotropic and homogeneous, the slab rests on a perfectly conducting ground plane, and the ambient medium is free space. Only one mode can propagate on a thin lossless slab, but more and more of the higher order modes begin to propagate when one increases the thickness or the loss tangent of the slab. As the thickness and the loss are increased, the lowest order mode takes on the properties of the Zenneck wave. At the same time, the higher order modes take on the properties of a homogeneous plane wave propagating in the grazing direction in the slab. Among the most interesting properties of a surface wave are the attenuation constant and the phase velocity. Contour maps are included to show how these quantities depend on the thickness, permittivity, permeability and loss tangents of the ferrite slab. Additional insight is provided by graphs showing the root trajectories, cutoff boundaries and field distributions of the four lowest order surface-wave modes.

A geometrical theory of diffraction for a half plane residing on the interface between dissimilar media: Transverse magnetic polarized case

An asymptotic ray analysis of the diffraction of an electromagnetic plane wave by a perfectly conducting half plane that resides on the interface separating half spaces filled with dissimilar media is developed for the case where the plane of incidence is perpendicular to the edge. The diffraction problem is formulated as an integral equation whose unknown is the tangential component of electric field residing on the uncovered half of the interface plane. This integral equation is solved by using the Wiener‐Hopf technique. Asymptotic analysis of the resulting diffracted fields is carried out in the angular spectral plane and ray interpretations are assigned to the asymptotic terms. In addition to geometrical optics and edge‐diffracted field components, which arise in the Sommerfeld diffraction problem, a lateral wave field is found to contribute to the total (asymptotically evaluated) field. The possibility for a Zenneck wave to be present arises also when the media exhibit magnetic contrast, although this possibility is not explored in the present paper.

Lateral electromagnetic waves along plane boundaries: A summarizing approach

Lateral electromagnetic waves along a plane boundary between homogeneous half-spaces are reviewed. The electromagnetic fields generated by vertical and horizontal electric dipoles near the boundary between air and the earth (salt or fresh water, soil, ice, etc.) are summarized in terms of a new unified theory of lateral-wave propagation. Complete theoretically determined fields are displayed and compared with measured fields at f = 601 MHz relative to the boundary between air and salt water (σ = 3.5 S/m, e r = 80). Near, intermediate, and asymptotic fields are related graphically to the new general theory and to the approximate and restricted formulas of Norton and Banos as well as to the Zenneck wave. Application is made to the specific problem of communication with submerged submarines by means of transmitters consisting of electrically short monopoles in air and horizontal traveling-wave antennas and directional arrays in sea water. The properties of the antennas are evaluated in the frequency range 10 ≤ f ≤ 30 kHz which is optimum for receiver depths near 10 m, and at f = 1 kHz which is optimum for depths up to 50 m. The effects of reflections from the ionosphere and of the earth's curvature are not included.

On the excitation of the Zenneck surface wave over the ground at 10 MHz

Using a planar earth model the infinite vertical aperture with a Zenneck wave variation is found to excite only the Zenneck wave with no radiation field. The finite vertical aperture excites a field which is similar to the Zenneck wave near the aperture but resembles the usual ground wave at large distances. Numerical results for various aperture heights are given for a frequency of 10 MHz for a homogeneous ground path.

Excitation of the HF surface wave by vertical and horizontal antennas

Using a spherical earth model, we develop a normal mode analysis for the excitation by an azimuthally symmetric source region. We then specialize the general formulation to deal with a vertical antenna with a prescribed current distribution. In particular, we consider the current distribution that would excite a pure Zenneck wave on the corresponding planar earth model. But we also consider excitation by vertical electric dipole and a uniform current distribution. Finally, we examine a horizontal antenna that is excited by a traveling current wave. Our general conclusion is that the Zenneck wave aperture illumination (i.e., current distribution) is a poor choice for enhancing the ground wave over a spherical earth. This point is illustrated for specific calculations at a frequency of 1 and 10 MHz over both land and sea.

Excitation of the Zenneck surface wave by a vertical aperture

Excitation of the Zenneck wave is examined for both finite and infinit vertical apertures over a homogeneous conducting flat ground. The infinit vertical aperture with a Zenneck wave variation is found to excite only the Zenneck wave with no radiation field. The finite vertical aperture excites a field which is similar to the Zenneck wave near the aperture but resembles the usual ground wave at large distances. Numerical results for various aperture heights are given for frequencies of 1 and 10 MHz. Both homogeneous ground and sea water paths are considered.

Modal theory of long horizontal wire structures above the earth: 2, Properties of discrete modes

The characteristics of the discrete propagation modes on horizontal thin‐wire structures located above a dissipative earth are investigated. In addition to the well‐known transmission line mode, a new root of the characteristic equation is found which is identified as a “surface‐attached” mode because of its close connection with the Sommerfeld pole (Zenneck wave) in some parameter ranges. Under many conditions the surface‐attached mode suffers substantially less attenuation along the propagation direction than does the transmission line mode. Numerical investigation of the propagation constants of the two modes is made, and field plots for the modes for a variety of wire parameters are presented.

Surface waves

The paper is an attempt to present, in the simplest possible terms, a unified picture of the theory of various forms of surface wave and a clear physical interpretation of their behaviour.The Zenneck wave, the radial cylindrical surface wave and the Sommerfeld-Goubau or axial cylindrical surface wave are each discussed and shown to represent basically one and the same phenomenon. The link with the Brewster angle, for which a wave incident on a surface suffers no reflection, is clearly established. The transition from a TEM wave supported by a parallel-strip transmission line, with metal plates close together, to two Zenneck waves independently supported by the plates, when these are separated by a very large distance, is demonstrated.The effect of bends in the supporting surface is considered, and methods of reducing radiation are explained.Finally the principles governing the launching of surface waves are surveyed with particular reference to the Brewster-angle approach.

The Physical Reality of Zenneck's Surface Wave

The first part of the paper shows that a vertical dipole does not generate a surface wave which at great distances behaves like Zenneck's plane surface wave. In Parts Two and Three it is shown that it is not necessary to call upon the Zenneck wave to explain the success of the wave antennas.