Triply degenerate surface waves in the metamaterial plate

A triply degenerate surface wave has been shown to exist in the metamaterial plate with the electrodynamic parameters ɛ₀= −1.036… and μ₀ > −0.964… The behavioral features of the field excited by a point source located near the plate have been revealed under the assumption that the plate parameters tend to resonant quantities and ɛ₀ and μ₀.     

Low-frequency resonances in hollow metamaterial cylinders

The 2D problem of excitation of a hollow circular metamaterial cylinder by a filament source is analytically and numerically investigated. It is found that, when the relative permittivity and permeability are close to minus unity, high-Q resonances exist in hollow cylinders of an electrically small radius. Near- and far-field patterns are calculated. It is found that, under resonance conditions, a multilobe scattering pattern typical of superdirective antennas is formed. The influence of loss on the resonance characteristics is investigated.     

High-Q resonances due to surface waves and their effects on theperformances of corrugated horns

We present a study of high-Q resonance phenomena that occur in corrugated horn structures. It is found that high-Q resonances occur within certain frequency bands where two types of modes, i.e., space-wave and surface-wave modes, simultaneously propagate. A simple model is presented to explain the resonance mechanism. The model yields the conditions for resonance, explains the Q of the resonance, and provides the associated resonant frequency. Approximate formulas for the upper and lower bound frequencies of a resonant band are obtained. It is found that the high-Q resonances deteriorate the gain and crosspolar performances of a horn even if the return losses are acceptable at some resonant frequencies. Rectangular corrugated horns are more susceptible to these resonances than circular corrugated horns, and the reasons for such a difference are explained     

A metamaterial based on a 2D two-element lattice of cylinders with right- and left-handed surface conductivity

A new method is proposed for calculating the effective constitutive parameters of small-period 2D lattices. A two-element lattice of resonance chiral cylindrical scatterers with the opposite signs of chirality is investigated. It is found that such a structure exhibits the properties of the Veselago medium in a narrow frequency band.     

Directional coupling of magnetostatic surface waves in layered magnetic thin films

The propagation characteristics of magnetostatic surface waves (m.s.s.w.) in a layered system of y.i.g. film, dielectric, y.i.g. film, are theoretically investigated. It is shown that the directional coupling of m.s.s.w. is possible between y.i.g. films. The directional coupling has frequency filtering characteristics due to dispersion of m.s.s.w.     

Propagation of electromagnetic waves in a nonlinear metamaterial layer

Propagation of electromagnetic TE waves in a nonlinear dielectric layer with generalized Kerr’s nonlinearity is considered. The layer is located between two isotropic nonmagnetic semi-infinite media with constant electrodynamic parameters. The dispersion equation for the eigenvalues of the problem (propagation constants) is derived. The behavior of dispersion curves is qualitatively analyzed. Propagation of waves in a nonlinear metamaterial is studied.     

一种C波段压控超材料表面

提出了一种C波段透射率可调的压控超材料表面。该超材料表面由加载变容二极管的新型可调超材料单元构成,通过直流偏置电压控制变容二极管的电容值,调节超材料单元的电磁特性。通过仿真并计算超材料单元的散射系数、等效介电常数和等效磁导率,该单元的可调谐振频域为5.2~5.6 GHz。将压控超材料表面与微带天线相结合,超材料表面透射率可改变天线远场辐射方向图,通过其对远场辐射方向图的调节,验证了可调超材料表面的性能。对设计的压控超材料表面加0.5~10 V的直流偏置电压,该超材料表面工作频率为5.4 GHz,其透射率能有效调节20 dB。     

Two-frequency resonance scattering by finite thin metamaterial plates

A finite thin plate made from a metamaterial with negative values of permittivity ? and permeability ?? is considered. The 2D problem of excitation of the plate by a cylindrical wave is numerically investigated. It is found that the frequency dependence of the excited near field has two high-Q resonances closely spaced in frequency and that the constitutive parameters have values close to those that lead to triple (double) degeneration of a surface wave in an infinite plate. The near and far fields at the resonance frequencies are calculated.     

Investigation of wide-angle thin metamaterial absorber at infrared region

In the practical application, a wide-angle absorption with simple structure is still crucial property of metamaterial absorbers (MAs). A single-band infrared MA is introduced to analyze the angle insensitive mechanism. Numerical simulation reveals that a perfect absorption peak with 99.9% (7.55 μm) is achieved at normal incidence, as well as the absorptivity is respectively 69.7% (7.46 μm) and 93.5% (7.46 μm) for transverse electric (TE) and transverse magnetic (TM) modes at 70° incidence. By changing substrate thickness, the absorption ratio at 70° is increased to 91% (7.46 μm) for TE mode. Our design can also keep the good absorption stability for the geometric parameters. The Ez-field distributions for different incident angles are given to investigate the physical mechanism. The designed MA can realize good wide-angle tolerance. This MA owns great applications, including infrared spectroscopy, solar harvester and plasmonic sensors.     

Diffraction of plane and cylindrical waves by a metamaterial cylinder

Rigorous solution of the problem of plane- and cylindrical-wave scattering by a circular cylinder made from a metamaterial is presented. It is shown that, inside a metamaterial cylinder, a symmetric caustic of refracted geometrical-optics rays with one cuspidal point is formed. The influence of the position of a cylindrical-wave source and the absolute value of the refractive index of the metamaterial both on the scattering pattern and the near field structure is studied.     

Diffraction of electromagnetic waves by the boundary of a semi-infinite metamaterial

Diffraction of plane waves at the interface of two semi-infinite regions is considered for the case when one of the regions is filled with a metamaterial in the form of a 3D periodic lattice of dipole-type particles. The diffraction problem is solved via the method of compensating sources, which is extended to the case of 3D structures. Different formulations of the diffraction problem that is reduced to either a system of Wiener-Hopf functional equations or a system of linear algebraic equations are presented. Representation of a semi-infinite structure by a sequence of layers characterized by wave transmission matrices is analyzed. It is shown that such matrices can be used to obtain the solution to the diffraction problem in an explicit form.     

Optically nonlinear waves in thin films

A new treatment of the behavior of TE nonlinear waves in an optically nonlinear film is given. The new mathematical results are expressed in terms of the physical parameters of the system and represent a straightforward way to introduce the necessary Jacobian elliptic functions. The optical nonlinearity is of the Kerr type and the numerical calculations are performed for a self-focusing medium. Dispersion curves labeled with optical power density at the lower film boundary, detailed plots of the variation of electric field amplitude as the wave number changes, and details of the power distribution across the guide are given. Since two values of a wave number can exist for the same power level and power thresholds exist, the system is of device interest in the area of optical switching.     

Scattering from conducting finite cylinders with thin coatings

The surface equivalence principle is used to develop an integral equation formulation for electromagnetic scattering from open circular cylinders with thin material coatings. The method of moments with entire domain functions leads to an algebraic system of equations which is solved numerically. Results of calculations for various cylinder aspect ratios, layer thicknesses, and material constitutive properties are presented.     

Scattering of electromagnetic waves by rough perfectly conducting circular cylinders

A numerical method is proposed for computing the normalized correlation functions of the real and imaginary parts of the field scattered from a statistically rough perfectly conducting circular cylinder. The deviation of the surface from its mean radius is assumed to be small. The correlation function of the far-field is related to the correlation function of the scattering object by an integral equation. Far-field correlation functions are found for two types of surface correlation functions: the delta function and a periodic exponential function.     

Magnetostatic surface oscillations in elliptical cavities and cylinders

The theory of magnetostatic surface oscillations (MSSOs) in elliptical cavities and cylinders is developed. Expressions for magnetostatic potentials and magnetic fields are obtained and force lines of the magnetic field are plotted. It is shown that the MSSOs in an elliptical cylinder and an elliptical cavity have the same frequency spectrum, whereas the field’s polarization in the region outside the ferrite changes from left-hand elliptical to right-hand elliptical. MSSO magnetostatic resonators are analyzed, and values of their eigenfrequencies and quality factors are compared to experimental data. The theory is also used to interpret the ferromagnetic-resonance spectra of nanowires.     

Travelling waves on thin bodies

Simple formulas for locating the travelling wave peaks in the backscattering patterns of thin three- and two-dimensional bodies are developed and compared.     

Standing spin waves in ferromagnetic thin films

A theory of spin wave resonance in ferromagnetic thin films is discussed in a manner that permits a computation of the real and imaginary parts of the circularly polarized RF fields as well as the power absorption spectrum. The case of the dc field intensity applied normal to the surface of the film is considered, and the saturation magnetization is taken as constant throughout the body of the film. Variations in dc fields near the surfaces are treated in the boundary conditions for the RF magnetization by considering the unsymmetrical nature of the exchange interaction at the surfaces. The boundary conditions are characterized by a constant for each surface that controls the degree of surface pinning in the RF magnetization. Damping is included in the formulation by means of a phenomenological constant in the spin wave equation and by simulaneous solution of this equation with Maxwell's equations for a conductor. The results of a computer program are presented showing the roles of the various parameters in determining the power absorption spectrum and RF fields. A comparison with experimental spectra is made, and an anomalous resonance at field intensities higher than that for the principal resonance is predicted.     

Scattering from cylinders with arbitrary surface impedance

This paper presents an integral equation method for the solution of the field scattered by a set of cylinders with arbitrary cross-sectional shape, and arbitrarily varying anisotropic surface impedance. The integral equations are given for an arbitrary source with arbitrary harmonic variation along the cylinder axis. The scattering problem can be solved for arbitrary three-dimensional sources by expansion of the source in a Fourier integral over the axial propagation constant. The integral equations have been programmed for a CDC 1604A computer. The program developed has been used to solve a great variety of scattering, antenna, and propagation problems, and, depending upon accuracy desired, will handle cylinders up to about 150-wavelengths total perimeter. Numerical results on scattering from cylinders with specific cross sections are presented to illustrate the utility of the program developed.     

Scattering of electromagnetic waves by arrays of conducting and dielectric cylinders

A method is developed that enables the solution of scattering by a finite number of cylinders in a convenient and accurate form. It is based on an analytic formulation using the boundary value problem and an application of a point matching technique. The method is then applied to study the scattering properties of both conducting and dielectric cylinders. It is also used to determine the size and spacing of passive scatterers to improve the directivity of linear antennas. In the latter case, a combination of the present method and a space perturbation technique is utilized to optimize the antenna gain.     

Computing scattering amplitudes for arbitrary cylinders under incident plane waves

A numerical method to compute scattering amplitudes for time harmonic waves scattered from infinite cylinders with arbitrary uniform cross section is described. A nonlocal boundary condition is used to develop a variational formulation of the scattering problem, and the finite element method is applied to determine approximations to the near field. Scattering amplitudes are then determined by means of an integral representation obtained from Green's formula and properties of the nonlocal boundary operator. Computational results are presented to illustrate the method's application.