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EMI shielding

Frequency‑domain EMI shielding of precision nickel mesh, 30 MHz – 16 GHz

A 400‑count NP1 mesh delivers 65–75 dB attenuation across the 5G/defence‑relevant band from 30 MHz to 16 GHz, with a floor of 65 dB at ~11 GHz and a ceiling of 75 dB across 30 MHz – 500 MHz.

GTX Research · EMI desk21 April 202613 minCC-BY-4.0ScholarlyArticle

1. Setup

Measurements were performed at IIT Delhi using an ASTM D4935‑18 dual‑TEM cell paired with a Keysight N5227B Performance Network Analyzer (PNA) calibrated 30 MHz – 16 GHz. Samples: 400‑count woven NP1 mesh, 0.025 mm wire, aperture 36 µm. Three coupon replicates per frequency band; results reported as mean ± 1σ.

2. Shielding spectrum

Fig. 1 — Shielding effectiveness vs frequency, 400‑count NP1 mesh.

The 65 dB floor at ~11 GHz corresponds to the first‑order diffraction limit of the 36 µm aperture. The flat 75 dB plateau below 500 MHz is bulk‑conduction‑dominated.

3. Application envelopes

  • 5G mid‑band (3.5–6 GHz) — 68–70 dB, comfortable margin for base‑station enclosures.
  • Defence X/Ku band (8–12 GHz) — 65–68 dB, qualifies for AESA enclosure shielding.
  • Connected‑device VHF (30–300 MHz) — 75 dB, ceiling of commodity envelope.
Attenuation band
65–75 dB
30 MHz – 16 GHz, 400‑count NP1.
Mesh count
400
Woven, plain.
Wire diameter
0.025 mm
NP1, 99.99 % purity.
Standard
ASTM D4935‑18
Dual‑TEM cell.

Sources & references

  1. ASTM International. D4935‑18 Standard Test Method for Measuring Electromagnetic Shielding Effectiveness. astm.org
  2. IIT Delhi EMI laboratory. 2025 sweeps, Keysight N5227B PNA.