Modal Network Synthesis for Arbitrary Interconnection Structures Including Radiation

A modal equivalent circuit for arbitrary interconnection structures including radiation is presented for the first time. The governing matrix equation of the discrete system representation obtained by the method of moments is solved exactly employing the eigenmodes of the quasi-static system. Due to the inherent radiation losses, the modes are mutually coupled, which has not been considered in all recently presented models and which is found to be responsible for the observed limitations. The network modelling includes the physical-based rational approximation of the intrinsic system dynamic, which is independent of the port positions. These in turn represent modal weighting factors, modelled by a transformer network. The model order is significantly reduced by the approximation of all sub-resonant (higher) modes by lumped elements. The accuracy and flexibility of the proposed SPICE-compatible equivalent circuit are shown by full-wave reference simulation in time-domain, including non-linear terminations.