Related Pages: Nodal Waveguide Interface
This tutorial focuses on setting up two nodal waveguide interfaces and computing the 4x4 renormalized S-parameter matrix between the main and mezzanine boards. The differential S-parameter matrix can be viewed by exporting the renormalized S-parameters to a touchstone file, then importing them into a circuit tool for combination and plotting.
Each board consists of a five layer PCB with two signal vias for the differential lines and two grounding vias. All parts were created with XF's modeling options. Metals and dielectric materials were created as normal, nondispersive material definitions and the waveform covers the project's frequency range of interest between 20 and 26 GHz. The minimum cell size of 4 mil allows two cells across the vertical thickness of the copper traces and ground planes.
Two nodal waveguide interfaces are created for the mezzanine and main boards. In each interface, the two pins of the differential stripline pair are identified and a reference plane offset is applied to de-embed the length of the transmission lines. When creating a simulation, a reference impedance of 50 Ω is specified.
The 4x4 renormalized S-parameter matrix is viewed and touchstone file export is demonstrated.