Cylindrical Dielectric Layer Research Articles

Mode Transformation in a Circular Waveguide With a Transverse Boundary Between a Vacuum and a Partially Dielectric Area

We consider the mode transformation in a circular waveguide with a transverse boundary between a vacuum part and a part with a cylindrical dielectric layer and a vacuum channel. Two situations are analyzed: an incident mode is launched on the boundary from the dielectric part of the waveguide or from the vacuum one. The incident mode is assumed to be both propagating and evanescent. Analysis is performed using the mode decomposition technique. Approximate solutions are obtained for the cases of the narrow channel and the case of the thin dielectric layer. A numerical algorithm for calculating the mode transformation at an arbitrary channel radius is developed. Typical dependences of the reflection and transmission coefficients on the channel radius are presented and discussed. It is shown, in particular, that the interaction of the evanescent mode with the boundary can result in excitation of the propagating modes in the reflected and transmitted fields.

Stacked dielectric tubes with electromechanically controlled radii

This work examines the features and capabilities of a tube comprised of stacked cylindrical dielectric layers separated by flexible electrodes with the applicative aim of electrically controlling the inner radius. The study begins with the analysis of the non-homogenous electromechanical response of a single-layer dielectric tube according to well-established coupled models. Two boundary conditions are examined - traction free boundaries and a fixed outer radius. The advantages and limitations of each boundary conditions are discussed. It is shown that dielectric tubes subjected to traction free boundaries experience instabilities, an effect that can be avoided by fixing the outer surface. Next, the electromechanical behavior of a stacked cylindrical actuator comprised of dielectric tubes that are mechanically connected in series and electrically connected in parallel is determined under the two boundary conditions discussed above. It is shown that the stacking of cylindrical layers increases the range of available inner radii at the cost of design limitations. Interestingly, it is found that mounting layers on a stacked cylindrical actuator may lead to instabilities even if the outer radius is fixed.

A Variation Model Option for the Heat Breakdown of Solid Dielectric Layer Under Constant Voltage

An idealy structured solid dielectric material formally has zero electrical conductivity (later on conductivity) and does carry an electric current. However real materials, used as solid dielectrics, have relatively low, but still finite conductivity, which, generally, increases with increasing temperature. Conductivity of solid dielectrics versus temperature corresponds to the exponential function, which by sight corresponds to the formula for Boltzmann distribution of microparticles in energy levels. In case there is a constant difference of potentials on the dielectric layer surfaces an electric current flows through this layer, causing Joule heat, which, under steady-state conditions, should be removed to the external environment. Inadequate heat removal rate leads to increasing temperature of dielectric, its increasing conductivity and electric current density, thereby increasing the volumetric capacity of the energy release in the dielectric, i.e. a positive feedback effect occurs to cause a quick growth of temperature culminating in the heat destruction of dielectric material (melting, carbonization). This process is called heat breakdown of the dielectric, apart from the electric breakdown. Investigation of conditions for emerging dielectric heat breakdown is associated with the analysis of rather complicated nonlinear mathematical model that permits an analytical solution in a closed form only for a flat or cylindrical dielectric layer through simplifying a dependence of dielectric conductivity on the temperature. In this paper, the model is assigned to a variational form that contains a functional. An analysis of stationary points of this functional allows us to find a combination of parameters that determine the ultimate state of the dielectric layer before the heat breakdown, in particular so-called breakdown voltage.

Semi-Analytical Model for the Transient Operation of Gate-All-Around Charge-Trap Memories

We present a detailed semi-analytical investigation of the transient dynamics of gate-all-around (GAA) charge-trap memories. To this aim, the Poisson equation is solved in cylindrical coordinates, and a modification of the well-known Fowler-Nordheim formula is proposed for tunneling through cylindrical dielectric layers. Analytical results are validated by experimental data on devices with different gate stack compositions, considering a quite extended range of gate biases and times. Finally, the model is used for a parametric analysis of the GAA cell, highlighting the effect of device curvature on both program/erase and retention.

EM-Wave Scattering by an Axial Slot on a Circular PEC Cylinder With an Eccentrically Layered Inner Coating: A Dual-Series Solution for TE Polarization

A dual-series approach is used to formulate scattering of a TE-polarized plane wave by a circular, PEC cylinder, having a longitudinal slot and enclosing two, eccentric, cylindrical dielectric layers. The dual-series equations are analytically regularized to a matrix Fredholm equation of the second kind by use of the Abel integral-transform method. The resulting infinite set of linear algebraic equations (i.s.l.a.e.) is truncated and solved numerically. The aforementioned analytical-numerical solution intrinsically takes into consideration the correct edge behavior of the field. Furthermore, the addition theorem of cylindrical wave functions is used to match the field components on any cylindrical interface. The numerical application manifests how the structure of the inner loading of this cylindrical cavity is imprinted on backscattering. Moreover, it is shown how the location of the innermost dielectric cylinder may contribute to the suppression or enhancement of resonances.

Tunable Omnidirectional Surface Plasmon Resonance in Cylindrical Plasmonic Structure

The tunable omnidirectional surface plasmon resonance in the optical range is theoretically demonstrated in a cylindrical plasmonic crystal by using rigorous coupled-wave analysis. The cylindrical plasmonic crystal consists of an infinite chain of two-dimensional cylindrical metal–dielectric–dielectric–metal structures. The dispersion relation of the cylindrical plasmonic crystal is obtained by calculating the absorptance as a function of a TM-polarized incident plane wave and its in-plane wave vector. The omnidirectional surface plasmon resonance can be tuned from UV region to visible region by adjusting the thickness of the cylindrical dielectric layers. The absorption spectrum of the infinite chain of nanocylinders is also investigated for comparison.

Diffraction of a coaxial resonator’s hybrid modes by a transverse slot and a cylindrical dielectric layer

The partial-domain method is applied to theoretically solve the problem of diffraction of a hybrid resonance mode by an inner ring slot and a cylindrical dielectric layer in a coaxial cavity with perfectly conducting walls of a finite thickness. The boundary equations for field amplitudes are solved with the use of Tikhonov’s regularization method, and a stable algorithm of calculation of the complex wave number (i.e., the resonance frequency and Q factor of free field oscillations) is developed. Conditions for the energy balance on the slot in the presence of a resonance are considered. Being independent of the field equations, these conditions complement them.

Cerenkov radiation fields in an inhomogeneously filled circular waveguide

Cerenkov radiation fields excited in a partially filled circular waveguide with a channel in which an electron beam propagates are studied. The surface of the channel is covered by a thin quasi-conducting layer to remove the electrostatic charge due to the beam passage. The effect of the thickness of the cylindrical dielectric layer is investigated. The thin quasi-conducting layer is shown to attenuate the Cerenkov waves generated in the lossless medium only slightly.

Effects of cylindrical dielectric layer systems on the radiation from an electric line source

This paper studies ab initio the classical radiation from an electric line source located in cylindrical dielectric layered structures. Effects of the structures on the spontaneous radiation are investigated using the transfer matrix method. Both single and multiple layer structures are considered. It is shown that due to coherence the waves supported by the layer structures can influence the source radiation significantly. The effects are shown to be more profound in multi-layer structures. Furthermore, the comparison with the previous theoretical results obtained using the coupled wave theory reveals that although the two results agree qualitatively to each other, the general frequency response can be rather different. Potential applications in cylindrical quantum well lasers are also discussed.

Analysis of microstrip antennas on circular-cylindrical substrates with a dielectric overlay

The use of dyadic Green's functions and the moment method is explored for the solution of microstrip antenna problems on circular cylindrical substrates. The dyadic Green's functions of the electric type are obtained for a medium consisting of three cylindrical dielectric layers concentric with a perfectly conducting cylinder, and integral equations are developed for the evaluation of the electromagnetic fields. The effect of a dielectric overlay on the resonant frequency of a cylindrical-rectangular microstrip antenna is analyzed. The patch is directly fed by means of a microstripline printed along the cylinder axial direction. The results show that the effect of the dielectric overlay is substantial when its relative permittivity and thickness are increased, such that this effect has to be very carefully considered in the design of microstrip antennas.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Equivalence relation between partial angular harmonic and ray-type Green's functions for a cylindrical dielectric layer

The relation between Green's functions appropriate to closed and open shells is explored. The problem of constructing a rigorous reference solution for multiple reflected-ray fields traversing a section of a curved layer is addressed by exploiting the connection between traveling-wave (ray-type) and standing-wave (angular harmonic) fields in the closed layer. Utilizing Poisson summation, the discrete superposition of standing wave fields is converted into a discrete superposition of spectral integrals whose asymptotic evaluation generates traveling waves. It is possible to group together the spectral integrals that correspond to the collection of ray fields with N reflections inside the cavity, and to express this sum alternatively, and exactly, in angular harmonic form. The quality of the asymptotic (i.e. ray) approximation obtained from the spectral integrals can be checked against numerical data from the harmonic series. This problem strategy is implemented for the two-dimensional canonical configuration comprising a circular cylindrical homogeneous dielectric layer excited by an axially directed electric line current source located in the interior cavity surrounded by the layer.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Gaussian beam analysis of propagation from an extended plane aperture distribution through dielectric layers. II. Circular cylindrical layer

For pt.I see ibid., vol.38, no.10, p.1607-17 (1990). The theory developed in pt.I of this paper for transmission of fields from an extended planar aperture through a plane dielectric layer is applied to transmission from such an aperture through an arbitrarily located cylindrical dielectric layer. By the self-consistency considerations enunciated previously, it is argued that the narrow-beam algorithm for near and far zone fields is truly predictive, although no other reference solution is now available for an independent check. As in pt.I, the aperture distributions are smoothly tapered or abruptly truncated, and they may generate beam tilts and focusing in the layer or its vicinity. >

Rigorous asymptotic analysis of transmission through a curved dielectric slab

A circular cylindrical dielectric layer is an idealized but rigorously analyzable model for radome covers. With a line source located on the concave side, an exact integral formulation is derived for the field transmitted to the convex side. Alternative representations are developed therefrom in terms of discrete guided modes and continuous spectra, and of ray integrals which, asymptotically at high frequencies, yield geometric optical fields that experience multiple internal reflections between the layer boundaries and also multiple reflections on the concave side. It is then shown that the higher order multiple reflected contributions can be expressed collectively as a ray field with a weighted transmission coefficient that is equivalent to the plane wave transmission coefficient for a plane parallel layer but includes a simple curvature correction. When source and observer are close to the inner and outer layer boundaries, respectively, and are also separated by a large angular interval, guided mode effects may have to be included as well. The result is a general and novel representation of the transmitted field in terms of a certain number of ordinary multiple reflected geometric optical ray fields, a single "collective" ray field, which includes in a composite manner all of the remaining internal reflections, and, possibly, the guided modes along the layer.