Abstract-A simple and efficient ftnite.element method for the analysis or microwave and optical waveguiding problems is formulated using three components of the electric or magnetic field . In order to eliminate spurious solutions, edge elements are introduced. In the edge element approach the nodal parameters are not limited to the magnetic fi eld as in the conventional three-component formulation ror the dielectric waveguiding problem. An eigenvalue equation derived here involves only the edge variables in the transversal plane and ca n provide a direct solution ror the propagation constant. To show the vailidity and usefulness of this approach, computed results are illustrated fo r microstrlp transmission lines and dielectric waveguides.
I. I NTRODUCTIONTO RIGOROUSLY evaluate propagat ion characteris-1. tics of microwave and optical wavegu ides with arbitrarily shaped cross sections, vectorial wave analys is is necessary , and different types o f the vector finit e-element method (FEM) have been developed . Of the various formulations, the FEM using full vector H field is quite suitable for a wide range of practical, complicated problems [I ] -[ I OJ . Thi s approach has been widely used fo r various dielectric waveguiding structures in microwave , millimeter-wave , and optical wavelength regions, and recently has been utilized as the waveguide solver of CAD packages [7] . The most serious problem associated with this approach is the appearance of spurious solutions. The penalty fun ction method [31. [4] , (6) , [7] has been used to cure this problem, but in this technique an arbitrary positi ve constant , ca lled the penalty coeffi cient , is involved and the accuracy of solutions depends on its magnitude . Funhennore, in the full vectorial fonnulation [1]-[10] the propagat ion conslant is fi rsl given as an inpul datum , and subsequently the operating frequency is obtained as a solution. More recently, several methods for solving directly the propagation constant have been developed , but each has its drawback, e.g., a large number of field components (11] -[13) , consideration of the adjoint fi eld which does not correspond to the actual electromagnet ic field [14], o r the need to estimate the line integral in the varialional expression [1 5). IEEE' Log Nu mber9104779.In this paper a simple and efficient FEM fo r the analysis of microwave and optical waveguiding problems is formulated using three components of the electric or magnetic fi eld. [n order to el iminate spurious solut ions and 10 treat arbitrarily shaped waveguidcs, triangu la r edge elements are introduced . An e igenvalue equation derived here invo lves only the edge variables in the transversal plane and can prov ide a direct solution fo r the propagation constant. To show the validity and usefulness of this approach, examples are computed fo r microstrip transmission lines on isolropic or ani sotropic substrates, dielectric rectangular wavegu ides, and equi lateral triangular core waveguides.
II . B ASIC EQUATIONSWe consider a dielectric...