The Complete Spectrum of Coplanar Waveguide and its Application to Scattering Problems

The fundamental and the parasitic mode of coplanar guide, fig. 1), have been extensively investigated [1]. Due to its open nature, the guide also features a continuum of radiation modes both in air and in the dielectric substrate which is excited by discontinuities such as steps, bends, short circuits, etc. Various common discontinuities in the guide couple strongly to these radiation modes. Such fields propagate without attenuation a long way away from their source and are difficult to handle by standard numerical techniques. This part of the spectrum has never been investigated before. This contribution deals with the continuum of coplanar guide in full hybrid form, including the effect of finite metallisation thickness. Its simple application to the problem of scattering by transverse metal strips is also treated, providing details of the radiation patterns. Cascades of strips, including interaction via the radiation field, are currently under investigation.