Engineering CalculatorsEMC Aperture & Vent Panel Shielding Calculator
Leakage through openings in an EMC shield — a thin slot or gap (radiating-aperture theory), or a vent panel/honeycomb with real depth (waveguide-below-cutoff), pairing EMC shielding with cooling vent design.
New to Radiating-Aperture & Waveguide-Below-Cutoff Theory? Read the guide: Apertures & Vent Panels: Why Openings Set Your Real EMC Shielding — a plain-language explainer of the standard behind this calculator.
Two distinct models, from the Acorn EMC Design Guidelines (Gibling, 1993), a standard EMC-course-style reference: a thin slot/gap (negligible depth) radiates like a slot antenna, SE = 20·log₁₀(λ/(2·d)) — d is the opening's maximum linear dimension, not its area, and SE reaches 0dB once d equals half a wavelength. A vent panel or honeycomb with real depth is instead modelled as an array of short waveguide-below-cutoff sections — each hole attenuates by k·(t/D) dB (k=32 round/hex, 27.3 square), and N close-packed holes lose a further 10·log₁₀(N) dB versus a single hole, per the same source. This tool deliberately does not implement the source's more granular hole-spacing (centre-to-centre distance C) formula — the scanned original was internally inconsistent about which terms carry a squared exponent, so the unambiguous hole-count form (stated clearly in the source's prose as "proportional to the square root of N") is used instead. Neither model covers gasket/seam contact impedance, which depends on the specific gasket material and compression and needs manufacturer data. A real enclosure's achievable shielding is normally set by whichever opening is weakest — pair this with the Shielding Effectiveness calculator for the solid-barrier number, and the Enclosure Cavity Resonance calculator for resonance effects.
Validated: the slot/gap formula reproduces the primary source's own published Table 2 (max slot length for 20dB shielding at 30/100/300/500/1000MHz — 457/152/51/30/15mm) to within 0.8dB of 20dB at every point; SE is exactly 0dB at and beyond d=λ/2. The vent-panel formula reproduces an independently-sourced worked example (6mm-diameter round hole, 20mm depth → 106.67dB) exactly, and the array-reduction term was checked to give exactly 10·log₁₀(4)=6.02dB less shielding for 4 holes versus 1 (matching "proportional to √N"). The cutoff-frequency formula fc=c/(1.706·D) was checked against the independently-published circular-waveguide TE11 result.