Electromagnetic Waves In Waveguide Research Articles

Perturbation Method in the Theory of Propagation of Two-Frequency Electromagnetic Waves in a Nonlinear Waveguide I: TE-TE Waves

The article deals with the problem of propagation of a two-frequency electromagnetic wave in a waveguide filled with a nonlinear medium. A two-frequency wave is the sum of two monochromatic TE waves with different frequencies. The permittivity of the waveguide is characterized by a very general nonlinearity function corresponding to self-action effects. It is shown that, under certain conditions, the two-frequency wave is an eigenmode of the waveguide. From a mathematical point of view, the problem reduces to a nonlinear two-parameter eigenvalue problem for the system of (nonlinear) Maxwell’s equations. The main result of the article is the proof of the existence of nonlinearizable solutions of the problem.

Radar Cross-Section Reduction of Helical Antenna by Replacing Metal With 3-D Printed Zirconia Ceramic

This letter proposes a dielectric helical antenna made of three-dimensional (3-D) printed zirconia ceramic, which possesses a better performance than the conventional metal one. On the one hand, the radiation principle of the proposed antenna is investigated by regarding its structure as a dielectric waveguide. It is found that a dielectric waveguide operating at the cut-off state of higher mode, here is TM01 mode, can radiate electromagnetic (EM) waves. The propagation constant of EM waves in waveguide is extracted to demonstrate that the dielectric waveguide indeed works as a fast-wave status at this moment. On the other hand, both the far-field and scattering performances between the proposed and conventional helical antennas are comparatively studied. It is observed that the structure composed of dielectric helix and metal ground can achieve similar radiation gain, axial ratio (AR), and AR bandwidth as the conventional all-metal helical antenna, but possessing lower radar cross section at high frequency. Benefited from a ceramic stereolithography apparatus, the proposed structure can be fabricated precisely, and measured results have reasonably validated the simulated ones.

The working standard of the unit of power of electromagnetic waves in the frequency range from 37,5 to 220 GHz

The possibility of using bolometric converters of microwave power from the State primary standard of the unit of power of electromagnetic waves in waveguide and coaxial paths GET 167-2017, which has a frequency range from 37,5 to 78,33 GHz, in an extended frequency range up to 220 GHz, is shown. Studies of semiconductor bolometric converters of microwave power in an extended frequency range have confirmed good agreement and smooth frequency characteristics of the effective efficiency factor of the converters. Based on the research results, the State working standard of the unit of power of electromagnetic waves of 0,1–10 mW in the frequency range from 37,5 to 220 GHz 3.1.ZZT.0288.2018 was approved. The technical characteristics of the working standard of the unit of power of electromagnetic oscillations in an extended frequency range from 37,5 to 220 GHz are given.

Vector Potential of Electromagnetic Wave above Strongly Inductive Two-Layer Earth Surface

Vertical components of the vector potential of electromagnetic wave above two-layer strongly inductive impedance medium are determined. The solution is represented as a Sommerfeld integral. Singularities of such an integral are determined using effective parameters. The phase velocity of the surface electromagnetic wave is considered. It is shown that such a velocity is always less than the velocity of light in vacuum, so that the surface electromagnetic waves cannot be classified as the Zenneck waves for which the phase velocity is greater than the velocity of light (similarly to electromagnetic waves in waveguides).

Векторный потенциал электромагнитной волны над сильноиндуктивной двуслойной земной поверхностью

The vertical components of the vector potential of an electromagnetic wave for a two-layer strongly inductive impedance medium are determined. The solution is presented as the Sommerfeld integral. The singular points of this integral were determined using the effective parameters. The question of the phase speed of a surface electromagnetic wave is considered. It is shown that it is always less than the light speed in a vacuum. This means that surface electromagnetic waves are not Zenneck waves, whose phase speed is greater than the light speed, like electromagnetic waves in waveguides.

Dispersion effects in Fakir's bed of nails metamaterial waveguides

The propagation characteristics of electromagnetic waves in waveguides implemented using the “Fakir's bed of nails” are investigated both analytically and numerically. The classical metal walls of a parallel-plate waveguide are replaced by a Fakir's bed of nails metamaterial having arbitrary pin lengths on both walls; treated as a homogenized effective spatially dispersive dielectric. A modal analysis of the electromagnetic fields is presented for the first time, and dispersion expressions for the propagating modes are derived analytically and independently validated with full-wave numerical simulations. An equivalent transmission line model is also given, and similarities with the classical metal-dielectric-metal structure commonly used in optics are discussed.

Specific features of the propagation of electromagnetic waves in a waveguiding structure with superconducting film and metamaterial

The propagation of electromagnetic waves in a rectangular waveguide containing layers of common dielectric and metamaterial with a negative refractive index separated by a thin film of a superconductor of the second type in the mixed state is considered. The possibility of amplifiying waves at frequencies lower than the cutoff energy due to the energy of an Abrikosov vortex lattice moving in the superconductor is demonstrated.

Enhancement of evanescent waves in waveguides using metamaterials of negative permittivity and permeability

Electromagnetic waves in waveguides consisting of metamaterials with negative permittivity and permeability are analyzed. It is found that metamaterials can enhance the intensity of the evanescent waves in the cladding without altering the propagation constant of the waveguide for both TE and TM modes. This is a unique property of metamaterials. The enhancement factor increases with the increasing of the thickness of the metamaterial and saturates when complete surface polaritons were established at the interface between the metamaterial and the cladding. The enhancement effect can improve the performance of evanescent-wave-based waveguide devices.

Light-Induced Threshold Instability of Nematic Director in Cylindrical Waveguide

The dependence of director reorientation threshold on the parameters of electromagnetic wave in waveguide as well as director boundary conditions on the waveguide surface is obtained.

Broken Lorentz Invariance and Metric Description of Interactions in a Deformed Minkowski Space

We discuss the possible breakdown of Lorentz invariance—at distances greater than the Planck length—from both the theoretical and the phenomenological point of view. The theoretical tool to deal with such a problem is provided by a “deformation” of the Minkowski metric, with parameters dependent on the energy of the physical system considered. Such a deformed metric realizes, for any interaction, the “solidarity principle” between interactions and spacetime geometry (usually assumed for gravitation), according to which the peculiar features of every interaction determine—locally—its own spacetinie structure. The generalized theory of relativity, based on the locally deformed Minkowski spacetime, is called “deformed special relativity” (DSR). In the first part of the paper, we give the foundations and the basic laws of DSR. In the second part, we analyze some experimental data, which admit an interpretation in terms of the DSR formalism and are, therefore, candidates for displaying a breakdown of the Lorentz symmetry. They are (i) the superluminal propagation of evanescent electromagnetic waves in waveguides, (ii) the meanlife of the KS0, (iii) the Bose-Einstein correlation in pion production and (iv) the comparison of clock rates in the gravitational field of Earth. Such analysis provides us with the explicit forms of the related deformed metrics as functions of the energy, thus putting in evidence, in all four cases (and therefore for all four fundamental interactions), departures from the usual Minkowski metric. This preliminary evidence for a broken Lorentz invariance may be regarded as the signature of possible nonlocal effects involved in the processes examined. Moreover, the corresponding deformed metrics obtained by our analysis provide an effective dynamical description of the interactions (at least in the energy range considered).

Wave-function method used to study the Bethe coupler.

The Bethe coupler is reinvestigated by use of the wavefunction method for the propagation of the electromagnetic waves in waveguides. The directivity of the secondary guide and the coupling factor are derived by computing the transmission coefficients through the hole of the coupler. A comparison is made with the standard results. \textcopyright{} 1996 The American Physical Society.

Transient electromagnetic wave propagation in waveguides

This paper focuses on propagation of transient electromagnetic waves in waveguides of general cross section with perfectly conducting walls. The solution of the transient wave propagation problem relies on a wave splitting technique, which has been frequently used in direct and inverse scattering problems during the last decade. The field in the waveguide is represented as a time convolution of a Green function and the excitation. Some numerical computations illustrate the method. A new way of calculating the first precursor in a Lorentz medium is presented. This method, which is not based upon the classical asymptotic methods, gives an expression of the first precursor at all depths in the medium. The excitation of the waveguide modes for time dependent sources is also addressed.

Exact, closed-form expressions for transient fields in homogeneously filled waveguides

It is well known that transient electromagnetic waves in waveguides exhibit dispersion. Exact, closed-form expressions, which involve Bessel functions of the first kind, have been derived for the impulse response of a waveguide, but exact, closed-form expressions for more complex pulses are absent from the literature. In this paper, it is demonstrated that incomplete Lipschitz-Hankel integrals can be used to represent transient pulses in homogeneously filled waveguides. A continuous wave pulse is investigated in this paper, however, this technique can also be applied to a number of other transient waveforms. The resulting expressions are verified by numerically integrating the pulse distribution multiplied by the known impulse response.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mode Characteristics in Chirowaveguides with Constant Impedance Walls

Modal propagation of electromagnetic waves in waveguides filled with chiral media, known as chirowaveguides, is studied. The waveguide walls are assumed to behave as constant impedance surfaces. This can model corrugated surfaces, dielectric coated metallic surfaces, as well as perfectly or imperfectly conducting walls. Conditions leading to modes with pure circular polarization are derived. Under these conditions, a chirowaveguide can act as a low crosspolar feed for reflector antennas.

Electromagnetic Waves in Waveguide Partially Filled with Semiconductor Plasma

AbstractThe dispersion of electromagnetic waves in waveguides partially filled with semiconductor plasma is investigated for unmagnetized and for strongly magnetized plasma.The effects which may be useful for the plasma electronics are found: In such waveguides there exist a large number of slow waves with typical frequencies ω ≈ ωP/√ϵL. The filling at which the different modes at fixed phase velocity are maximum separated in wavelength is found. The thickness of the semiconductor layer at which this effect arises is about hundred micrometers and depends on the crystals' type. In addition to this, in strongly magnetized semiconductor plasma the maximum frequency separation of the typical plasma waves is found at fixed filling.Is it shown that in such systems there exist many surface waves which are of the slow wave type.In the case of strongly magnetized plasma coupling between nonsymmetrical EH‐ and HE‐ modes is shown to exist.

Nonsymmetrical Electromagnetic Waves in Partially Plasma — Filled Waveguide

AbstractThe dispersion of nonsymmetrical electromagnetic waves in waveguide, partially filled with plasma, is studied numerically and experimentally. An external d.c. coaxial magnetic field is applied to the waveguide. The dispersion equation of these waves is obtained, and it is solved numerically for the experimental conditions. Results are obtained, which show coupling of the waveguide HEl1‐modes with the family of the high‐frequency plasma HEln‐modes. The numerical dispersion curves are experimentally examined, and the influence of the magnetic field and the plasma density is studied.

A finite element method for solving Helmholtz type equations in waveguides and other unbounded domains

A finite element method is described for solving Helmholtz type boundary value problems in unbounded regions, including those with infinite boundaries. Typical examples include the propagation of acoustic or electromagnetic waves in waveguides. The radiation condition at infinity is based on separation of variables and differs from the classical Sommerfeld radiation condition. It is shown that the problem may be replaced by a boundary value problem on a fixed bounded domain. The behavior of the solution near infinity is incorporated in a nonlocal boundary condition. This problem is given a weak or variational formulation, and the finite element method is then applied. It is proved that optimal error estimates hold.

A potential scattering formulation for mode couplings of electromagnetic waves in waveguides

A formulation for the propagation of electromagnetic waves in waveguides is developed in the mathematical frame work of quantum mechanics. Mode-coupling problems are then treated as potential scatterings. In particular, an interacting Hamiltonian with scattering potential is analytically derived for the mode couplings due to a bend in a waveguide. The formulation can be generalized to thin-film waveguides and waveguides of arbitrary geometry.

Electromagnetic waves in waveguides, containing azimuthally magnetized ferrite

In this paper, electromagnetic waves in circular waveguides, containing azimuthally magnetized ferrite are investigated. It is found out that in these waveguides, right hand and left hand circularly polarized waves have the same propagation constants. Consequently, these waveguides can be used as polarization insensitive phase shifters instead of rotators.

Optical rectification effect and its applications (review)

A review is given of theoretical and experimental investigations of the optical rectification effect (ORE) in nonlinear crystals. Attention is focused on aspects of using this effect for measurements of the nonlinear susceptibilities of crystals, measurements of the power, polarization, and profile of laser pulses, excitation of electromagnetic waves in waveguides and resonators, generation of infrared radiation, and nonlinear spectroscopy. Further potential uses of the ORE are discussed.