Longitudinal Section Electric Research Articles

New insights on Titan's plasma-driven Schumann resonance inferred from Huygens and Cassini data

After a preliminary analysis of the low-frequency data collected with the electric antenna of the Permittivity, Wave and Altimetry (PWA) experiment onboard the Huygens Probe that landed on Titan on 14 January, 2005, it was anticipated in a previous article [Béghin et al., 2007. A Schumann-like resonance on Titan driven by Saturn's magnetosphere possibly revealed by the Huygens Probe. Icarus, 191, 251–266] that the Extremely Low-Frequency (ELF) signal at around 36 Hz observed throughout the descent, might have been generated in the upper ionosphere of Titan, driven by a plasma instability mechanism associated with the co-rotating Kronian plasma flow. The involved process was proposed as the most likely source of a Schumann resonance in the moon's atmospheric cavity, the second eigenmode of which is actually found by models to occur at around 36 Hz. In this paper, we present a thorough analysis of this signal based upon the Huygens Probe attitude data deduced from the Descent Imager Spectral Radiometer (DISR), and relevant measurements obtained from the Radio Plasma Wave Science (RPWS) experiment and from the magnetometer (MAG) onboard Cassini orbiter during flybys of Titan. We have derived several coherent characteristics of the signal which confirm the validity of the mechanism initially proposed and provide new and significant insights about such a unique type of Schumann resonance in the solar system. Indeed, the 36 Hz signal contains all the characteristics of a polarized wave, with the measured electric field horizontal component modulated by the antenna rotation, and an altitude profile in agreement with a Longitudinal Section Electric (LSE) eigenmode of the atmospheric cavity. In contrast to Earth's conditions where the conventional Transverse Magnetic mode is considered, the LSE mode appears to be the only one complying with the observations and the unexpected peculiar conditions on Titan. These conditions are essentially the lack of any lightning activity that can be ascertained from Cassini observations, the presence of an ionized layer centered around 62 km altitude that was discovered by the PWA instrumentation, and the existence of a subsurface conducting boundary which is mandatory for trapping ELF waves. A simple theoretical model derived from our analysis places tentatively consequential constraints on the conductivity profile in the lower ionosphere. It is also consistent with the presence of a conductive water ocean below an icy crust some tens of kilometers thick.

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.

Uniform Long-Slit Microwave Plasma Generation From a Longitudinal-Section Electric Mode Coupling

A stable uniform long-slit atmospheric argon plasma is produced by coupling a longitudinal-section electric (LSE) mode in a dielectric-loaded rectangular waveguide. The microwave-induced plasma discharge system consists of a 2.45-GHz microwave source, a circulator, a three-stub tuner, a transformer, and a tapered rectangular waveguide loaded with two dielectric slabs. A uniform 98-mm-long atmospheric argon plasma is observed at a relatively low microwave power level of 350 W and a gas flow rate of 10-15 L/min

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

Hamiltonian symplectic semi-analytical method and its application in inhomogeneous electromagnetic waveguides

Dual vectors are applied in Hamilton system of applied mechanics. Electric and magnetic field vectors are the dual vectors in electromagnetic field. The Hamilton system method is introduced into the analysis of electromagnetism waveguide with inhomogeneous materials. The transverse electric and magnetic fields are regarded as the dual. The basic equations are solved in Hamilton system and symplectic geometry. With the Hamilton variational principle, the symplectic semi-analytical equations are derived and preserve their symplectic structures. The given numerical example demonstrates the solution of LSE (Longitudinal Section Electric) mode in a dielectric waveguide.

Dielectric property measurement using a resonant nonradiative dielectric waveguide structure

This letter describes a new dielectric characterization technique, based on the resonant nonradiative waveguide structure described by Yoneyama and Nishida , for permittivity measurements at microwave and mm-wave frequencies. The measurement system is modeled as a resonator comprised of two parallel conducting plates with a rectangular dielectric slab sandwiched in-between. Resonant frequencies of the longitudinal section electric (LSE) modes and the unloaded Q of the cavity are used to determine the permittivity of the dielectric and its loss tangent, respectively. The technique is shown to be accurate for measuring the dielectric properties of a wide array of polymer and oxide materials. For materials with small dielectric loss tangents, an accuracy of better than /spl plusmn/0.4% is attained in the measurement of the relative dielectric constant of the material.

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.

Dyadic Green's functions for curved waveguides and cavities and their reformulation

Dyadic Green's functions (DGFs) for continuously curved waveguides are important for the feeding and radiation problems of cylindrically conformal slotted‐waveguide arrays. The major difficulty in the construction of these DGFs in curved waveguides and cavities is that there are no entire‐domain TE or TM modes with respect to the curving direction, while the longitudinal‐section electric (LSE) and magnetic (LSM) modes do not have the complete orthogonality in terms of the dot product as required by the conventional Ohm‐Rayleigh method as practiced in literature. Therefore, the conventional Ohm‐Rayleigh method for constructing DGFs is not applicable to curved waveguides. In this work, the DGFs are constructed with the help of the Lorentz reciprocity theorem and the mode orthogonality based on the concept of power flow, and by adding the source singularity terms. To reduce the orders of singularity of DGFs in their application to waveguide walls, the common form of DGFs is then reformulated into a form convenient for numerical computation by both forward and backward derivation procedures. Finally, a general procedure is proposed for the reformulation of DGFs for common types of waveguides. The DGFs derived are applicable to problems with curved waveguide junctions, and coupling and radiating slots for conformal slotted‐waveguide antennas.

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.

Generalized admittance matrix analysis of cylindrical cavities coupled by rectangular apertures

The generalized admittance matrix (GAM) approach to the analysis of cylindrical cavities coupled to external waveguides by rectangular apertures is discussed. Green's dyad of the admittance type under the longitudinal section electric (LSE) field approximation is derived and GAM is obtained by Galerkin's method. Several numerical results are presented and a criterion for the optimal mode selection is discussed. A reduced formulation having improved efficiency is derived and its use is critically discussed. Comparisons with results of mode-matching, finite-element method and with measurements are shown. The analysis is successfully applied to waveguide bandpass filter design.

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.

Measurement and Modeling of the Apparent Characteristic Impedance of Microstrip

Voltage and current cannot be defined uniquely for microstrip except at zero frequency, and therefore microstrip has not been rigorously incorporated into circuit theory. However, in engineering practice, micro-strip exhibits an apparent characteristic impedance, denoted here by ZA, that can be measured. Three methods of measuring ZA were devised and used in measuring three impedance levels of microstrip. These methods are described and experimental results presented. The measurements of ZA were found to be consistent with the power-current characteristic impedance definition of the approximate longitudinal-section electric (LSE) model of nricrostrip. Simple approximate formulas for representing ZA are also discussed.

Microwave Absorption due to the Geometric Resonance of the LSE Surface Wave in a Wave Guide

Microwave absorption due to the longitudinal-section electric (LSE) modes is considered for a semiconductor-slab loaded in a wave guide. The absorption gets maximum when the fundamental LSE surface-wave is strongly excited and resonates geometrically inside the slab. The conditions for occurrence of the strong absorption depend remarkably on frequency and the size of the slab, but are adjustable by variation of magnetic field value and carrier densities. These absorptions explain quite well the results observed near cyclotron resonance fields for Ge-slabs by Otsuka et al.

Analysis of Microstrip-Like Transmission Lines by Nonuniform Discretization of Integral Equations

The nonuniform discretization of the integral equation on the tangential electromagnetic (EM) field on the boundary surface is proposed as a numerically efficient method to analyze the microstrip-like transmission lines. The calculated results of the propagation constant of the microstrip line based on this method are compared with other published analytical results. Various types of planar striplines are treated by the same formulas. The dominant and higher order modes of shielded microstrip line are discussed and compared with the longitudinal-section electric (LSE) and linear synchronous motor (LSM) modes of a two-medium waveguide.

On the Design of Dielectric Loaded Waveguides

Rectangular waveguides partially filled with a dielectric slab in the E plane can provide an alternative to ridged waveguides in broad-band systems. It is shown that by an appropriate choice of the dielectric constant, maximum power handling capacity for a given bandwidth and cutoff wavelength can be achieved. This power-handling capacity is much higher than for ridged waveguides. Attenuation and the effect of the first longitudinal-section-electric (LSE) mode on bandwidth are also discussed.

Microstrip Dispersion Model

The assumption that the quasi-TEM mode on microstrip is primarily a single longitudinal-section electric (LSE) mode leads to a transmission line model whose dispersion behavior can be analyzed and related to that of microstrip. Appropriate approximations yield simple, closed-form expressions that allow slide-rule prediction of microstrip dispersion.