Compare 8 mm, 4 mm, 2 mm, 20 mil and 10 mil centre-to-centre spacing. Drag either view to rotate both boards; zoom in to inspect the via row.
Short-record diagnostic fields, with perfect conductors and a lossless dielectric. Full energy and pointwise field convergence are not established. This model excludes conducted supply/ground noise. The no-fence reference removes both the top ground guard and the via row, so this comparison tests their combined arrangement.
The colors are actual OpenEMS frequency-domain magnetic-field samples, divided by the complex source-loop current. Units are (A/m)/A = 1/m. One logarithmic scale is shared by every case and both frequencies. The 1 MHz view is a raw field diagnostic from the short impulse-response record; the numerical pickup figures below each board use the separate quasi-static extraction documented in the report.
The board is 18 × 16 mm. Top copper is at z = 1.2 mm and a solid ground plane is at z = 0 mm. Hiding ground only changes its visibility. There is no shielding lid. Via posts have a 0.127 mm diameter at every pitch. Metric rows end at ±8 mm; imperial rows end at ±8.128 mm. Vertical dimensions are not exaggerated.
The half-domain solution is mirrored using its PEC symmetry: Hx changes sign across x = 0; Hy and Hz do not. No factor of two is applied to fields. Copper uses the same model coordinates as the verified OpenEMS XML. The browser retains every fourth native x sample and every second y sample; all z samples are retained. Smooth display surfaces interpolate between those samples. Tiny via-gap field detail is limited by the solver mesh and display sampling.
Optional equal-length arrows show instantaneous H direction at the chosen phase relative to sinusoidal source current. They do not show field-line trajectories or a travelling transient. Magnitude colors do not change with phase. The 20 mil and 10 mil port results are close enough that their incremental benefit is unresolved by the previous mesh and record-length checks.
Field provenance and interpretation · Coupling report and limitations · Field-export verification