Propagation Wavenumbers for Half- and Full-Width Microstrip Lines in the ${ EH}_{1}$ Mode

Equations are presented for calculating the propagation wavenumbers for half- and full-width microstrip lines operating in the EH₁ mode. The transverse resonance method is used for determining the propagation wavenumbers. For the half-width microstrip line, only the self-admittance of the open edge needs to be considered. The self-admittance can be calculated from either the rigorous equations or the simplified formulas, both of which have been derived previously using the Wiener-Hopf method. However, for the full-width microstrip line, the mutual admittance between the two open edges of the microstrip line also needs to be considered. For the first time, the mutual admittance is calculated accurately with the spectral-domain immittance method, and approximately with a space-domain method. By accounting for the mutual admittance, the accuracy of the wavenumber of the full-width microstrip line is greatly improved.