Microwave Characterization of Microshield Lines

An experimental characterization of a new type of monolithic planar transmission line, the microshield, is presented. Theoretically, it is shown to have the tendency to radiate less than the conventional coplanar waveguide (CPW). To characterize the line, experimental measurement of a scattering parameters of the microwave model is essential. This paper presents characterization through the design, fabrication and measurement of the line and a discontinuity such as the two coupled open-end line. The frequency dependence of the effective dielectric constant is measured and compared to the computed values. Although proposed for applications at lower sub-mm-wave frequencies, fabrication in a hybrid fashion allows for use at microwave frequencies. Present applications of microshield technology are seen in Microtech Cascade probes and feed throughs for package connections in CPW interconnects. In addition, it is possible to use the microshield to connect MMIC's by designing the shield width to accommodate an MMIC. Therefore characterization of the microshield line and discontinuities is necessary.