Full-Wave Analysis of Microstrip Floating-Line Discontinuities

A full-wave analysis of the resonance generated by a floating line is presented. Beginning with the dyadic Green’s function for a dielectric stab, an integral equation is formulated. This integral equation is then solved by the method of moments in obtaining the transmission and reflection coefficients, as well as current distributions along the transmission line and on the floating line, both longitudinal and transverse. Employing these results, the near-and far-zone fields, as well as radiation patterns are computed. It was found that under resonance conditions the radiation power can exceed 13% of the feeding power, which may cause a potential problem in electromagnetic compatibility. Singularities involved in the Sommerfeld integrals are carried out by a novel pole extraction technique in conjunction with conventional folding methods. The new technique reduced the relative error of the singular integrals due to inaccurate pole position about one order in magnitude in comparison to the traditional approaches. To verify our new approach, a number of cases of open-ended transmission lines and gap discontinuities are examined. The results from our method showed good agreement with those of previous publications.