Low loss guided wave propagation in a left-handed microstrip structure using dispersive split ring?rod combination metamaterial

Split ring-rod combination metamaterial is used as a substrate material in a microstrip guided wave structure to determine what the effect is of a material with potentially excessive dispersion or loss or both. A Green's function method readily incorporates the metamaterial permittivity and permeability tensor characteristics. Ab initio calculations are performed to obtain the dispersion diagrams of several complex propagation constant modes of the structure. Analytical analysis is done for the design and interpretation of the results, which demonstrate remarkable potential for realistic use in high frequency electronics, while showing modes with extremely low loss bands.     

Characteristics of microstrip transmission lines withhigh-dielectric-constant substrates

An efficient numerical code is developed from a full-wave analysis in the Fourier transform domain to determine the characteristics of a single-strip or multistrip coplanar transmission line. Modes of both even and odd symmetries are included. The impedance of the transmission line is calculated using the power-current equivalent model. Coupling constants between the even and the odd modes are also calculated. Results are provided for a shielded two-strip coupled microstrip transmission line on high-dielectric-constant substrate such as lanthanum aluminate with applications to superconducting transmission lines     

On the application of complex resistive boundary conditions tomodel 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     

Relationships for Green's function spectral dyadics involvinganisotropic imperfect conductors embedded in layered anisotropic media

The Green's function spectral dyadic that characterizes a perfectly conducting patch antenna or propagating line can be modified to account for noninfinite conductivity. This is done through a relationship for a single planar interface imbedded in an anisotropic medium. A relationship for an arbitrary number of planar interfaces imbedded in an anisotropic medium is also derived. The imperfect conductor is represented by an anisotropic impedance     

Propagation in layered biased semiconductor structures based ontransport analysis

A transport-field parallel-plate formulation and solution method to determine the small-signal propagation constant is given for wide microstrip lines over an inhomogeneously doped semiconductor substrate of small transverse dimensions. Included in the detailed transport model are two carrier species, recombination-generation mechanisms, DC and AC field-dependent mobilities and diffusion constants, and boundary condition contact effects. A transverse DC bias condition is applied. Structures numerically simulated are a voltage-variable GaAs distributed Schottky-barrier phase shifter and a transmission line over an Si bipolar junction. Numerical data based on a finite-difference technique are generated on carrier densities, electric potentials and fields, and current densities. Propagation constant calculations compared favorably to those calculated by both full-wave field analysis and moments-of-the-Boltzmann-equation analysis for some less general cases. Propagation constant results for the GaAs structure are compared with available experimental data, and good agreement is obtained     

NNexus: An Automatic Linker for Collaborative Web-Based Corpora

In this paper, we introduce Noosphere Networked Entry eXtension and Unification System (NNexus), a generalization of the automatic linking engine of Noosphere (at PlanetMath.org) and the first system that automates the process of linking disparate "encyclopediardquo entries into a fully connected conceptual network. The main challenges of this problem space include: 1) linking quality (correctly identifying which terms to link and which entry to link to with minimal effort on the part of users), 2) efficiency and scalability, and 3) generalization to multiple knowledge bases and web-based information environment. We present the NNexus approach that utilizes subject classification and other metadata to address these challenges. We also present evaluation results demonstrating the effectiveness and efficiency of the approach and discuss ongoing and future directions of research.     

Electromagnetic-field theory and numerically generated results for propagation in left-handed guided-wave single-microstrip structures

Dispersion diagrams and magnetic- and electric-field distributions are found for a microstrip structure containing a simple left-handed medium (LHM). The LHM material constituting the substrate has characteristics chosen to overlap with potentially realizable substances. Calculations are done using a fast solver anisotropic Green's function spectral-domain computer code. The theoretical-field method, valid for complex layered structures and anisotropies in the LHM, underlying the computational procedure, which is critical for finding the dispersion diagrams and field distributions, is presented. It is found that the dispersion diagrams and field distributions are very unusual and admit the possibility of completely new device realizations based on combining LHM with conventional materials in a multilayered configuration.     

Voltage variable microwave phase shifter

Results are given on the fabrication, test and theory of operation of a voltage-controlled, continuously variable phase shifter designed to operate from DC to 150 GHz. The device was fabricated in a way that makes it compatible with current gallium arsenide monolithic microwave circuit technology.     

Analysis of ferrite circulators by 2-D finite-element and recursiveGreen's function techniques

Ferrite circulator operation is analyzed here by two techniques. The first employs a two-dimensional (2-D) finite-element (FE) technique, using a publicly available FE package. We show how to adapt this code to the solution of the magnetostatic equations and solve for the distribution of internal magnetic field inside a round ferrite puck of finite thickness, and use it to verify existing approximations for the demagnetizing fields. Additionally, the 2-D FE method has also been used to calculate the RF fields and scattering parameters in circulators having noncircular shapes, as well as nonuniform material properties and bias conditions. We have also investigated the field solutions for round circulators, calculated using a recursive Green's function (RGF) technique. This technique allows for radially varying properties in the material or bias fields, and thus accommodates the nonuniform demagnetizing field distribution in finite pucks. A comparison of the results of this technique with experiment is made. We show how the impedance-matching structures attached to the circulator affect the field distributions inside, and present plots of the field distributions as a function of frequency, which provide insight into circulator operation     

F.E.T. oscillation frequency domain solution

A new approach is used to determine when the necessary condition for oscillation, Re (Za)<0, holds in a microwave oscillator. Here Za is the Schottky GaAs f.e.t. active network impedance. This analysis has been used to develop a computer program that calculates the frequencies at which the above condition holds. The computer program also provides inband impedances and reflection coefficients and has been utilised to study Ku-band y.i.g.-tuned oscillators. Bandwidth and initial frequency of oscillation curves as functions of f.e.t.-model lumped elements are generated from the computer program.