Clifford M. Krowne

On the application of complex resistive boundary conditions to model transmission lines consisting of very thin superconductors

A resistive boundary condition for the case where the resistivity is assumed to be a complex quantity is shown to be an accurate model for a superconducting film which is thin compared to the super-conducting penetration depth. The imaginary part of the conductivity is the dominant terms and is a measure of the inductive energy stored in the superconductor. Numerical solutions of superconducting microstrip are obtained and compared to experimental results and to analytic solutions for superconducting parallel-plate waveguides. Excellent agreement is found between experimental, analytical, and numerical results. >

Electromagnetic theorems for complex anisotropic media

Complex anisotropic media can generally be described by a 6 \times 6 macroscopic constitutive tensor \hat{C} . Using \hat{C} properties, a reaction integral formula is derived from which an anisotropic reaction theorem (modified reciprocity theorem) is developed. Reduction of the \hat{C} medium into a reciprocal medium is discussed including tensor symmetry attributes and limiting cases. The anisotropic reaction theorem is utilized to derive a zero reaction theorem, and then treated in relation to the moment method. Mutual and self-impedance elements of a network are also derived in terms of reaction integrals, symmetry covered using the anisotropic reaction theorem, and impedance elements related to moment calculations. Use of spectral domain analysis is also covered.

Cylindrical-rectangular microstrip antenna

Resonant frequencies f_{r} of a cylindrical-rectangular microstrip antenna are theoretically calculated. Comparison is made to f_{r} for a planar rectangular patch antenna, including the simplest planar patch modes having no field variation normal to the patch surface. The validity of using planar antenna patches to characterize microstrip antennas is examined.

Fourier Transformed Matrix Method of Finding Propagation Characteristics of Complex Anisotropic Layered Media

A structure having arbitrarily located conductor lines immersed in complex anisotropic layered media presents one with a very general guided wave problem. This problem is solved here by a rigorous formulation technique characterizing each layer by a 6 x 6 constitutive tensor and finding the appropriate Fourier transformed Greens function matrix G. From G a method of moments solution for the propagation characteristics follows including propagation constant eigenvalues and field eigenvectors at all spatial locations.

Numerical Spectral Matrix Method for Propagation in General Layered Media: Application to Isotropic and Anisotropic Substrates

A full-wave analysis technique for generalized artisotropic layered media based on a 4x4 field matix method is applied to calculate the propagation constant of a number of microstriplike transmission structures. This technique is very versatile, and allows simultaneous permittivity, permeability, and optical activity anisotropy. Data for higher order modes of single and coupled strip lines in isotropic layered media in the millimeter-wave region are presented. New dispersion data for both low- and high-anisotropy dielectric layered structures are generated for different principal axis crystallographic orientations.

Green's function in the spectral domain for biaxial and uniaxial anisotropic planar dielectric structures

Greens function solutions of the biaxial and uniaxial anisotropic layered-medium planar-structure is formulated in terms of Maxwells equations. Diagonalized biaxial and uniaxial permittivity tensors in the coordinate system of interest are treated. The Greens function is found in the double Fourier transformed domain for three longitudinal-to-an-axis coupled electric-magnetic field sets applied to a simple layered structure. The approach is applicable to structures having discontinuities in two orthogonal planar directions such as patch radiators or resonators. Spectral Greens function is usable in method-of-moment calculations assisted by Galerkins method.

Restricted equivalence of paired epsilon–negative and mu–negative layers to a negative phase–velocity material (aliasleft–handed material)

Summary The time–harmonic electromagnetic responses of (a) a bilayer made of an epsilon–negative layer and a mu–negative layer, and (b) a single layer of a negative phase–velocity material are compared. Provided all layers are electrically thin, a restricted equivalence between (a) and (b) exists. The restricted equivalence depends on the linear polarization state and the transverse wavenumber. Implications for perfect lenses and parallel–plate waveguides are considered.

Determination of the Green's function in the spectral domain using a matrix method: Application to radiators or resonators immersed in a complex anisotropic layered medium

A planar structure having arbitrarily located conductor patches immersed in complex anisotropic layered media presents a very general field problem. This problem is solved here by a rigorous formulation technique characterizing each layer by a 6 \times 6 tensor and finding the appropriate Fourier transformed Greens function matrix G of 2n \times 2n size. The technique finds a set of field eigenvectors for each layer. Using G , a method of moments numerical solution for radiation characteristics of probe fed patch(es) can be had in the spectral domain employing, for example, a zero reaction method. Variation of real frequencies of the driving probe fed signal is allowed by that approach. Those workers desirous of radiator or resonator fields and frequency behavior at only selected resonant frequencies can use G to derive a matrix S_{X} given here. Setting the determinant of S_{X} equal to zero yields complex resonant frequency solutions, and the field solutions as a consequence to the nonprobe fed or free standing patch structure. The method is very versatile and can handle a large class of microwave or millimeter wave integrated circuit or monolithic circuit problems, no matter how simple or complex as long as they possess planar layers.

Unusual magnetoresistance in a topological insulator with a single ferromagnetic barrier

Tunneling surface current through a thin ferromagnetic barrier on a three-dimensional topological insulator is shown to possess an extraordinary response to the orientation of barrier magnetization. In contrast to conventional magnetoresistance devices that are sensitive to the relative alignment of two magnetic layers, a drastic change in the transmission current is achieved by a single layer when its magnetization rotates by 90°. Numerical estimations predict a giant magnetoresistance as large as 800% at room temperature with the proximate exchange energy of 40 meV at the barrier interface. When coupled with electrical control of magnetization direction, this phenomenon may be used to enhance the gating function with potentially sharp turn-on/off for low power applications.

Electromagnetic properties of nonreciprocal composite chiral-ferrite media

The theoretical properties of a composite chiral-ferrite medium are developed, The composite is constructed from a general chiral medium and a nonreciprocal ferrite medium. Application of the reaction theorem allows proof of nonreciprocity based on the constitutive relationships. Vector Helmholtz E- and H-field equations are derived, and from these equations reciprocal space Greens function dyadics are found. The direct space dyadics are then determined. Characteristic dispersion equations are found from the sourceless vector phasor Helmholtz equations. E-field polarization is obtained by projecting the E-field vector onto the polarization plane selected. Diagonalization of the elliptic equation through coordinate rotation allows major and minor axis determination. >