Effect of air gap on cylindrical dielectric resonator antenna operating in TM/sub 01/ mode

The results of a numerical study on the effect of an air gap on the input impedance and resonance frequency of a cylindrical dielectric resonator (CDR) antenna operating in the TM/sub 01/ mode as a function of dielectric constant are presented. The CDR resides on a conducting ground plane and is excited by a coaxial probe through the bottom of the ground plane. Some of the numerical results are validated experimentally.<>     

Scattering from a thin perfectly-conducting square plate

Extensive numerical experiments on the scattering from a thin perfectly conducting square plate have been carried out to assess the performance of the exact analytical expressions for the electromagnetic field of a rectangular patch with uniform and linear distributions of current, in connection with the method of moments. Two solution schemes, employing pulses and roof-top functions for approximating the surface current on the plate, have been used. Convergence rates and results for the two solution schemes are compared with each other, as well as with an efficient solution by A.W. Glisson and D.R. Wilton (1980). The overall performance indicated by the numerical experiments suggests that it would be useful to use the exact numerical expressions in the solution of problems where accurate computation of the field radiated by such current sources is required     

Potential integrals for uniform and linear source distributions on polygonal and polyhedral domains

Formulas for the potentials due to uniform and Linearly varying source distributions defined on simply shaped domains are systematically developed and presented. Domains considered are infinite planar strips, infinite cylinders of polygonal cross sections, planar surfaces with polygonal boundaries, and volumetric regions with polyhedral boundaries. The expressions obtained are compact in form and their application in the numerical solution of electromagnetics problems by the method of moments is illustrated.     

Accurate impedance model for antiresonant monopoles on finiteground planes

A simple and accurate procedure based upon reaction theory is presented for computing the input impedance of a monopole antenna backed by a finite ground plane. This procedure is used to finally verify theoretically some of the controversial antiresonant measured input impedances presented by Meier and Summers in their classic 1949 work     

Influence of central valley effective mass and alloy scattering on transient drift velocity in Ga1?xInxP1?yAsy

The instantaneous ensemble-averaged and time-averaged velocity of electrons are presented for Ga0.27In0.73P0.4As0.6, and the results are compared to those for GaAs. The results indicate that both the effective mass in the ? conduction band and alloy scattering are very critical in determining the transient (or velocity-overshoot) characteristic as well as the static velocity-field characteristic for this quaternary material.     

Circuit effects in time-of-flight diffusivity measurements

A Monte Carlo procedure is used to examine certain effects that interfere with the determination of the diffusivity D from current rise and fall times in a time-of-flight experiment. It is found that electron bombardment time, sample capacitance, contact resistance, and oscilloscope rise time can cause considerable error in the measurement of D, especially near the threshold electric field. It is shown that a reasonable accounting for these effects can explain much of the difference between experimentally-and theoretically-determined D-E characteristics for GaAs.     

Energy bandgap and lattice constant contours of iii–v quaternary alloys

Energy band gap and lattice constant contours are presented for the nine quaternary alloys formed from Al, Ga, In and P, As, Sb. The quaternary bandgaps were obtained using an interpolation formula proposed by Moonet al. The quater nary lattice constants were obtained by use of a linear interpolation technique using the binary lattice constants as boundary values. This work was supported by a research grant from the Office of Naval Research, Washington, D.C.