Longitudinal Section Magnetic Research Articles

Concept of terahertz waveguide plasmon amplifier based on a metal groove with active graphene

We propose a concept of terahertz waveguide plasmon amplifier based on a metal groove with active graphene. It is shown that the power amplification factor of the longitudinal-section magnetic (LSM) waveguide plasmon (normalized to its wavelength) near the cut-off frequency of this mode can exceed the amplification factor of the transverse magnetic (TM) plasmon in a layered graphene structure by more than four orders of magnitude for the same frequency. This is caused by the increase of the LSM plasmon wavelength near the cut-off frequency, smaller energy velocity of the LSM mode, and greater energy release from graphene for the LSM plasmon due to stronger lateral confinement of the LSM waveguide plasmon as compared to the TM plasmon in a layered graphene structure. We show that the enhancement of the LSM plasmon amplification factor near the cut-off frequency is a stronger effect than that due to screening of graphene.

Guidance and Leakage Properties of Higher-Order Modes in NRD-Guide and H-Guide With Bianisotropic Split Ring Resonator Metamaterials

A rigorous full wave analysis of nonradiative dielectric guide and H-guide with split ring resonator metamaterials is presented to investigate the different dispersion properties. As is shown, some abnormal higher-order longitudinal-section magnetic (LSM) and longitudinal-section electric (LSE) modes with negative slope of the phase constant versus frequency may come into existence when metamaterials are double negative. Such modes will eventually lead to the leakage. However, for other LSM/LSE modes, leakage can be greatly reduced by utilizing the bianisotropic effects. Particularly, when the metamaterials are of single negative parameters, leakage elimination can be achieved.

Nonradiative dielectric waveguide embedded in metamaterial with negative permittivity or permeability

AbstractA nonradiative dielectric waveguide (NRD) embedded in a metamaterial with negative permittivity or permeability is proposed and theoretically characterized in this work. This dielectric waveguide structure is inherently nonradiating at bends and discontinuities, since metamaterials with negative permittivity or permeability cannot support any propagating modes. The waveguide supports hybrid longitudinal section magnetic (LSM) and longitudinal section electric (LSE) modes. It is demonstrated that the LSM11 mode is the lowest‐order mode when the waveguide dimensions are properly designed. The theoretical results indicate that this guided‐wave structure is able to narrowly confine electromagnetic fields within the core dielectric strip, thus exhibiting nonradiating properties. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 207–210, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20771

Dipole-mode wakefields in dielectric-loaded rectangular waveguide accelerating structures.

By applying different symmetric boundary conditions, we found that the transverse wakefields generated by an electron bunch traveling through a partially loaded rectangular dielectric structure at an off center position can be decomposed into corresponding orthogonal longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes for guided waves as in the case of longitudinal wakefields treated previously. The wakefields are characterized using the normalized shunt impedance R/Q, a function of the geometry of the accelerating structure, for both LSE and LSM modes. A numerical example is given for an X-band waveguide structure and detailed results are given for the several leading transverse wakefield terms. The analytic results obtained are in agreement with the results from the time domain simulation tool MAFIA.

Mode-Matching Analysis of Waveguide T-Junction Loaded With an H-Plane Dielectric Slab - Abstract

This paper presents a full-wave mode-matching analysis of a rectangular waveguide T-junction partially loaded with an H-plane dielectric slab. First, the longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes in an H-plane dielectric-filled rectangular waveguide are obtained. Second, the dielectric-loaded T-junction is then divided into four regions and their electromagnetic fields are expanded into the summation of their modal functions using the resonator method. Finally, a mode-matching process for the tangential field components across regional interfaces is carried out to derive the generalized scattering matrix of the waveguide T-junction. Using the cascading connection technique of generalized scattering matrix, various waveguide couplers and power dividers/combiners with H-plane dielectric slabs can be easily analyzed and designed. Numerical results are presented and compared with those obtained by measurement or Ansoft's HFSS. Good agreement is observed.

Fdtd Investigation of Quasi-Tem Hybrid Modes On Microstrip Lines

The inhomogeneous dielectric configuration of the microstrip line supports only Quasi-TEM hybrid modes. The mode-coupling efficiency between the longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes increases with frequency. Microstrip circuits can be analyzed assuming TEM modes but only below a frequency fstat. Theoretical formulas predict that undesirably strong coupling between the Quasi-TEM and TM0 modes, and the onset of the lowest-order surface wave TE0 mode occur at frequencies fTEM and fc,TEo' respectively. In this paper, the full-wave FDTD method shows the existence of the longitudinal field components, and verifies to a certain extent the validity of the operating frequency range as predicted by the theoretical formulas.

Complete characterization of transmission losses in generalized nonradiative dielectric (NRD) waveguide

In this paper, transmission losses of the generalized nonradiative dielectric (NRD) waveguide are modeled and presented by our closed-form equations for the design of hybrid and monolithic millimeter-wave integrated circuits. This generalized structure includes our recently proposed channelized NRD-guide. Parametric effects are studied with respect to complex propagation constant and characteristic impedance, and some useful guidelines are generated for practical design considerations. Calculated results are discussed separately for the conductor and dielectric losses for the two fundamental longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes. It is found that the LSE mode may have losses, in some cases, comparable or even smaller than those of its LSM counterpart, contradicting what has usually been perceived for the conventional NRD-guide design.

Full-wave analysis of a nonradiative dielectric waveguide with a pseudochiral Ω-slab

This paper presents a new microwave device - a non-radiative dielectric (NRD) waveguide with a dielectric pseudochiral /spl Omega/-slab - the /spl Omega/-NRD waveguide. A rigorous full-wave analysis is presented and the modal equations for the longitudinal-section magnetic (LSM) and longitudinal-section electric (LSE) modes are derived. The dispersion curves and operational diagrams for the first hybrid LSM modes are presented. The effect of the pseudochiral /spl Omega/-medium is discussed. New interesting modal features are revealed, showing that the propagation characteristics may differ considerably from the common isotropic case.

A Wiener-Hopf-type analysis of uniaxial substrate-superstrate microstrip structures

A Wiener-Hopf-type technique in conjunction with the hybrid-mode analysis and a space-domain Fourier transform pair was employed for the solution of the canonical problem of a TEM wave obliquely incident upon the edge and defined by a semi-infinite plate conductor lying at the interface of two uniaxial dielectrics, forming an otherwise grounded double-layer geometry. The single-cover layer and double-layer surface-wave modes' characteristic equations are examined and their cutoff conditions, along with safe conditions avoiding longitudinal-section magnetic (LSM) modes are given. The scattered field components and the TEM-wave reflection coefficient are given analytically in the form of Sommerfeld-type integrals. A thin layers approximation and a numerical integration scheme were adopted for the evaluation of the reflection coefficient. Its expression can be directly used for the analysis of wide microstrip lines and patch antennas printed in a substrate/superstrate geometry. The whole analysis gives a clear physical insight into the problem. Furthermore, a twofold theoretical verification was adopted by either forcing the absence of the superstrate or considering both layers to be isotropic. Numerical parametric Investigations show the effects of either the presence of the superstrate or both layers' dielectric anisotropy.

A new formulation of the boundary condition at infinity for a hybrid radiation mode and its application to the analysis of radiation modes of microstrip lines

A new formulation of the boundary condition at infinity for a hybrid radiation model is introduced. It is shown that its application leads to an iterative solution of the problem in the spectral domain. The validity of the condition is proved by its application to the analysis of a laterally shielded dielectric slab. Using this condition, an iterative method in the spectral domain is proposed in order to analyze striplike stratified transmission lines. As a result, two solutions, classified as perturbed longitudinal electric (LSE) and longitudinal section magnetic (LSM) modes, are obtained. Numerical results concerning the convergence of the method as well as the field distribution are presented for the case of a microstrip line.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Transverse operator study of a large class of multidielectric waveguides

The transverse operator method is described for the study of different kinds of dielectric waveguides. The longitudinal section electric (LSE) modes and longitudinal section magnetic (LSM) modes of a corresponding dielectric stratified waveguide, also known as TE-to-x and TM-to-x modes, have been chosen as the basis eigenfunctions, allowing rapid numerical convergence. The dispersion characteristics of some multidielectric waveguide structures have been obtained, as well as their attenuation constants. The results are compared to those previously published or measured and show good agreement. This formulation can be applied to other multidielectric structures with no modification.

Radiation impedance of a dipole printed on periodic dielectric slabs protruding over a ground plane in an infinite phased array

The radiation impedance of a dipole printed on periodic dielectric slabs standing over a ground plane in an infinite phased array is calculated. The calculation is made by means of modal expansions in terms of longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes. Derivations of these hybrid space modes and development of the modal expansions are presented first. The impedance of the dipole element is then calculated by a method based on the complex power relations with the aid of Poynting's theorem. The results calculated by the present theory in the limiting case of no dielectric slab loading have been compared with the results calculated by the method of ordinary plane wave expansions. A comparison is also made between results calculated by the theory and the experimental data obtained from waveguide simulators or test array. These results are shown to be in good agreement. An outline of steps to formulate the solution of the current distribution on dipole is also given.