Issue link: https://iconnect007.uberflip.com/i/1472851
54 DESIGN007 MAGAZINE I JULY 2022 In the beginning and even today, EM simula- tors are constantly in search of the right bal- ance between accuracy and speed to "mesh" a three-dimensional structure and acquire the right answer. In the search for the ultimate solution to Maxwell's equations, whether it is in the frequency domain for finite element methods (FEM) or in the time domain for finite difference time domain (FDTD), the user interface oen suffers. Setting up ports, boundary conditions, and mesh topology might give the guru user additional flexibility. For most of us, we need automation to reduce the repetitive tasks. e good news is the processing speed of modern computers and low-cost memory has made it much easier to maintain signifi- cant accuracy while increasing speeds. is has enabled increased investment in optimiz- ing user interfaces for specific applications, like simulating multi-layer laminate PCB designs. e improved user interfaces like Keysight's PathWave ADS SIPro and PIPro rely on robust importing of EDA PCB CAD data, which include stackup, nets, and com- ponents for easy selection of nets and com- ponents for simulation. Ports can be auto- matically assigned, and default meshing and boundary conditions enable users to be up and running with an EM simulation in a mat- ter of minutes. However, simulators are notorious for "gar- bage in equals garbage out." Here are a few tricks of the trade to ensure a proper setup: 1. A tip from Eric Bogatin: Know what to expect by turning your complex EM model into a simple cascade of transmis- sion lines and lumped components to get a quick idea of what the results might look like. 2. A tip from Lee Ritchey: Know what you paid for by creating a mechanical test structure where a trace is routed to the board edge on every layer, to visually check the layer-to-layer alignment, trace etch width, and mechanical height of the laminated layers. 3. My favorite tip from the measurement world: Measure something simple like a stepped impedance transition (the Beatty Standard) to verify dielectric material properties and check mechanical dimensions vs. algorithmic models and measurements. 4. A tip from the SI and PI world: Look at the data in both the time domain and the frequency domain. 5. Finally, put the model to work and check sensitivity to fabrication and component tolerances. Figure 2: Simple cascade of algorithmic transmission line models in a schematic to understand what wider trace capacitive discontinuities or narrower trace inductive discontinuities will do to the transmission of high frequency signals.