An enriched RWG basis for enforcing global current conservation in EM modelling of capacitance extraction

The RWG basis widely used in the discretisation of the EFIE is traditionally defined over interior edges of the structure's mesh when modelling charge-neutral scattering problems. In this paper, a careful extension to the RWG function space that allows for flow of current in and out of a structure via its boundary edges while maintaining current conservation is constructed. This space is appropriate for the computation of capacitance, where (i) a constant voltage difference is maintained between two components making up the device, and (ii) the total current is conserved. Using this basis implicitly enforces a constant potential difference between the metal plates (cf. natural boundary conditions), and explicitly places a restriction on the current (cf. essential boundary conditions). It improves upon the classic delta gap excitation of capacitive structures in that it is asymptotically independent of the triangulation used to describe the device's geometry.