Tutorial: Patch Antenna Design

This page connects the model that passes preflight in Your First Patch Antenna with the separate patch cross-check in validation/crossval/05_patch_antenna.py.

Place the ground plane as an explicit finite PEC box inside the domain, not as a full-domain PEC boundary wall: a finite ground plane radiates into the absorber beneath it, which is the open-radiation problem being modelled, while a PEC bottom wall makes the structure a closed cavity and shifts the resonance high.

python validation/crossval/05_patch_antenna.py

With the OpenEMS/CSXCAD Python bindings installed, the script prints a console summary comparing the rfx and OpenEMS resonances and writes a plot plus a JSON result file. Those bindings are not an rfx dependency: if they are missing, the script runs the rfx portion and then exits with status 2 behind a SKIPPED banner. That run is inconclusive and does not report a cross-solver pass.

• The script gates on three things, not two. Two are numeric: “rfx Harminv vs OpenEMS Harminv (resonance frequency) < 20 % (pass_vs_openems); rfx internal self-consistency < 5 % (pass_internal)” — a Harminv-vs-Harminv frequency agreement, not an |S11| magnitude match. The third is mode identification (pass_mode_id_rfx): every measured mode is assigned to its nearest declared TM_mn0 member, and the design member TM100 “must exist, be unique, and be accompanied by a member resolving the other in-plane axis”, inside a derived tolerance of 12.4988 % (sqrt(min adjacent declared member ratio) - 1). An rfx TM100 error beyond the log-symmetric window [-11.11 %, +12.50 %] “fails the case BY IDENTIFICATION, not by an accuracy gate”. The openEMS leg runs the same identifier but is reported, not gated.
• The 20 % openEMS bound is a smoke bound. The script’s own words: it “reports a coarse-mesh resonance and exercises the end-to-end path; it does NOT gate accuracy. Patch-accuracy evidence is delegated to the committed tests”. Those tests are the gate_paths in validation/crossval/manifest.json — tests/locks/test_patch_edgefed_resonance_harminv.py, tests/locks/test_patch_edgefed_s11_passivity.py, tests/oracle/test_patch_cavity_eps_oracle.py, tests/crossval/test_patch_canonical_farfield_e4.py — not this script’s exit code.
• Those tolerances and results apply only to the script’s geometry, mesh, frequency band, and metric. They do not validate the First Patch model or the patch gallery diagnostic.
• Use impedance-referenced S-parameter results only through a documented port workflow — see Sources & Ports for add_port. The lumped-port S11 dip in this script is a secondary check with a known single-cell parasitic reactance, so read it as a local dip near the Harminv frequency, not a deep matched null.
• Treat non-uniform mesh variants as limited support unless the page you are following says otherwise.