Recommended Configuration

Use this page to choose a starting setup and the right calculator for your port. Each calculator has its own limits, listed here. What you must check before reporting any result is on Cross-Validation and Accuracy.

For ordinary RF work, start from the uniform Cartesian Yee grid:

• boundary="cpml" for open problems and "pec" for closed ones;
• point sources, and the port family that matches your structure;
• probes, flux monitors, Harminv resonances, the port calculators below and the documented far-field workflows.

This is the configuration with the broadest evidence. A graded mesh, the ADI solver and multi-device runs each carry narrower limits, listed below and in Support Boundaries.

A port calculator only works for its own port family. Do not substitute one for another.

Port	Calculator	Start from	Limits
Lumped or wire add_port(...)	run(compute_s_params=True), or forward(port_s11_freqs=...) for a differentiable S11	about 60 cells per wavelength at the highest frequency	A discrete feed across one gap, not a modal line port. V is read at the port node and I half a cell toward the line, so a two-port S21 phase is referenced to the port separation less half a cell. Lumped and wire ports return the same S11.
Microstrip add_msl_port(...)	compute_msl_s_matrix(...)	at least 4 cells through the substrate (preflight warns below that)	Returns the raw extracted S; read sigma_max_excess for any passivity breach, or pass enforce_passivity=True to project it. Check probe_clearance for the probe layout and settling_db for the record length.
Rectangular waveguide add_waveguide_port(...)	compute_waveguide_s_matrix(...)	the documented rectangular-guide modes and bands	Single-mode magnitudes have the broadest evidence; phase, junctions, multimode and graded meshes have less. Only normalize=False and normalize="flux" carry a gradient.
Coaxial add_coaxial_port(...)	compute_coaxial_line_reflection(...) for one port, compute_coaxial_two_port(...) for a through line	at least 4 cells across the annulus	Exactly one coaxial port with face="top", precision="float32", a uniform 3-D grid and CPML on all six faces. The calculator builds its own line, source and probes; it is not a general coaxial-network solver.

Field sources, plane waves, probes, DFT planes and flux monitors have no port impedance or reference plane. They give fields and power, not S-parameters.

A transmission line should end at a port that absorbs it, not in the CPML. Name the conductor a port ends with terminates= on add_port, add_msl_port or add_coaxial_port; a microstrip port ends the strip under it by default. The CPML terminates a guided line much less well than a plane wave. Preflight names any conductor that runs into the absorber unterminated.

Configuration	What to know
Graded (non-uniform) mesh	Check the limit for each source, port and observable in Non-Uniform Mesh. A plane wave along a graded axis leaks into the scattered-field region (preflight warns); normal incidence along x needs a uniform x axis. add_refinement is refused on a graded mesh.
Local refinement, add_refinement	Takes effect only through run() on a uniform mesh. forward(), optimize(), topology_optimize() and the S-parameter calculators refuse a refined model.
Multi-device, run(devices=[...])	Uses the shard_map runner with exchange_interval=1. Lumped RLC elements, MSL ports, refinements, Kerr materials and DFT planes are refused.
Differentiable design	The objective is a proxy. Check the final design with a converged forward run of the RF quantity you report.

When a run argument is not implemented on the path your model takes (for example until_decay, snapshots or conformal walls on some paths), run() raises before the first step. Change the argument or the configuration; the message names both.

• A completed run is not a validated one. No warning does not mean converged, passive or correctly referenced. Work through the checklist on Cross-Validation and Accuracy.
• Examples and tests cover their own setup. A committed test pins behaviour at its own mesh, band and configuration.
• Coaxial results computed before the lanes absorbed on all three axes (cpml_axes="z", now refused) came from a line in a closed metal can and do not reproduce.