Quasi-TEM modes in parallel-line transmission structures with conductors embedded in dielectrics

Abstract

A transmission structure of many parallel conductors is capable of propagating many distinct quasi-TEM modes. A field theory of such modes was developed for a theoretically infinite number of very thin conductors placed on a dielectric substrate. The current paper extends this work to include a large number of thin parallel conductors embedded within finite dielectric slabs. The theory is illustrated by the following three structures: a large number of parallel wires embedded in dielectric slabs with substrates of infinite width, both with and without a ground plane; and a large number of thin wires embedded in a finite dielectric slab without a ground plane. This extension to a finite dielectric structure is obtained using a superposition method where both vertical and horizontal surfaces are considered infinite in turn. A major application of the derived formulation is the investigation of velocity distributions and crosstalk within these structures. Comparison of these structures with ones where the conductors are on the substrate (as opposed to embedded) indicates how the placement and structure of the conducting channel affects the modal velocities and crosstalk.