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42056b8331
Re-simulation infrastructure for the new 4-layer aperture-coupled antenna
stackup (Stack_Hybrid.png, committed 1de2296). Renders the full multilayer
geometry (L1 patch / L2 slot ground / L3 microstrip feed / L4 backplane)
on the actual substrate stack (RO4350B 0.508 mm + RO4450F 1.2 mm + RO4350B
0.11 mm) and runs FDTD via openEMS to characterize S11 vs frequency.
Geometry interpolated from existing 2-layer Gerber:
patch W from Gerber (7.854 mm, set by εr only)
patch L re-tunable for new substrate (env var PATCH_L_MM, default 7.25 mm)
slot/feed/stub fully parameterized via env vars
Run modes:
PROFILE=sanity : single run, λ/18 mesh, ~30 s
PROFILE=balanced : single run, λ/25 mesh, ~60 s
PROFILE=sweep : 5×5 grid over slot_L × stub_L, ~25 min
Env overrides for parametric exploration:
PATCH_W_MM, PATCH_L_MM, SLOT_L_MM, SLOT_W_MM, STUB_L_MM, SLOT_Y_OFF_MM
Setup: openEMS Python bindings built from source against /opt/openEMS for
Python 3.12 in radar_venv; run with
DYLD_LIBRARY_PATH=~/opt/openEMS/lib ~/radar_venv/bin/python
under cwd != openEMS-Project/openEMS/python (avoids CSXCAD shadow import).
Status: simulation infrastructure verified end-to-end; patch resonates at
10.4 GHz with W=9.0 / L=5.5–6.0 mm. Full 50 Ω impedance match not yet
converged — the L4 backplane (non-standard for aperture-coupled) reduces
slot coupling vs textbook formulas; needs proper EM optimizer (scipy
wrapping or CST/HFSS handoff) to fully tune. ~150 MHz baseline BW
predicted from substrate physics; 30/40 MHz chirp target comfortably
under any plausible match outcome.
