Nucula v2

Bare NFC coil measurement coupon

Open nfc-antenna.kicad_pro in KiCad 10. This 46 × 48 mm coupon contains the same reusable antenna footprint assigned to A1 in the main schematic. It is a passive two-terminal coil, without NFC controller, matching network or ground plane. It is not the main product PCB.

Fabrication assumptions:

• Two copper layers, 1.6 mm FR4, 35 µm finished copper per layer.
• Four turns, 40 × 40 mm outer winding copper, 0.50 mm traces / 0.30 mm gaps.
• Two plated 0.40 mm holes complete the bottom-layer return; do not make them NPTH.
• Retain soldermask over the windings and underpass. Expose only the feed pads shown in the mask Gerbers. The inner hole has no mask opening.
• No copper pours, metal backing, ferrite, components or added test loops.
• gerbers/ contains the copper/mask/silk/outline files and separate PTH/NPTH Excellon drill files. The NPTH drill file is intentionally empty.

Solder a short calibrated fixture to terminals 1 and 2 and measure while unpowered. The two terminals are expected to be DC-connected through the coil. Avoid adding a cable loop or measurement-fixture ground plane behind the coil. Save the raw impedance sweep, fixture calibration and final assembly environment.

See the design and tuning guide for measurements, calculations, limitations and how to use the footprint in the main layout. Native KiCad DRC and independent same-net clearance checks pass; RF behavior still requires measurement.

Regenerate the coupon using tools/nfc/check_coil.py with KiCad's pcbnew Python. This regenerates the .kicad_pcb and validation preview, so preserve any manual coupon changes first. Re-export Gerber/drill outputs after edits.