Previously the array sim only excited a single inner element
(DRIVEN_X / DRIVEN_Y). Adds DRIVEN_PORTS env var accepting a
comma/semicolon-separated list of "i,j" pairs that are all excited
in-phase with equal amplitude — models a perfect 1:N corporate
splitter feeding an N-patch sub-array.
Example: DRIVEN_PORTS="0,0;1,0;2,0;3,0;0,1;1,1;2,1;3,1" excites a
4-cols × 2-rows sub-array anchored in the corner.
S-parameter post-processing reframed for the multi-driven case:
each excited port reports active-S11 (uf_ref/uf_inc with all driven
ports active); each non-excited port reports S relative to a
representative driven port's incident wave (all driven ports have
equal amplitude so any reference works).
Backwards-compatible: empty DRIVEN_PORTS reverts to single-port
DRIVEN_X / DRIVEN_Y behaviour.
Single-port-driven, 15-port-terminated FDTD sim built on the same v3 patch
design point (W=7.854, L=6.56, FEED_OFFSET=2.14) at the Gerber pitch
(14.27 mm X / 15.01 mm Y). Reads out S_jd for all elements when port
(DRIVEN_X, DRIVEN_Y) is excited. Configurable array size + driven port via
env vars; default = 4x4, drive inner element (1,1).
Result at PROFILE=balanced, drive (1,1):
Active S11 @ 10.5 GHz : -16.7 dB, Z = 45.7 + j13.5 Ω
Active -10 dB BW : 190 MHz (10.44-10.63 GHz; ≈ single-element 180)
Nearest-neighbour coupling:
-x edge neighbour (0,1): -18.3 dB (strongest — edge element loads less)
-y/+y in-array : -22 dB
+x interior neighbour : -24.7 dB
Diagonal : -32 dB
Far corners : -45 to -53 dB
Outputs: coupling_grid.png heatmap + S_matrix.csv (all S_jd full sweep) +
S11_data.csv (driven-port only).
Known limitation: port box must align with mesh lines; SmoothMeshLines may
sub-cell-shift seed lines, causing some DRIVEN_X/DRIVEN_Y choices to give
"Unused primitive" warning + zero excitation. Default (1,1) is verified;
other choices are best-effort. Documented inline.
