Emi Table Calculator

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EMI Shielding Effectiveness Table Calculator

Analyze Electromagnetic Interference (EMI) attenuation across frequency spectrums

(Copper = 1.0)
(Air/Copper = 1.0)

Calculation Results

Freq (MHz) Absorption Loss (dB) Reflection Loss (dB) Total SE (dB)

Understanding EMI Shielding Effectiveness (SE)

Electromagnetic Interference (EMI) shielding is a critical engineering process used to block or attenuate electromagnetic fields within a space using barriers made of conductive or magnetic materials. This calculator determines the total Shielding Effectiveness (SE) in decibels (dB), which is the sum of three primary factors: Absorption Loss (A), Reflection Loss (R), and Multiple Reflection Correction (B).

The Physics of Shielding

When an electromagnetic wave hits a shield, part of it is reflected from the front surface, part is absorbed as it passes through the material, and part is reflected from the back surface. Our EMI Table Calculator focuses on the two dominant components:

  • Absorption Loss (A): This occurs as the energy of the wave is converted into heat within the shield material. It is directly proportional to the thickness of the shield and the square root of the frequency, conductivity, and permeability.
  • Reflection Loss (R): This depends on the impedance mismatch between the incident wave and the shield surface. It is higher for materials with high conductivity and lower for high-frequency waves.

Typical Material Constants

Material Rel. Conductivity (σr) Rel. Permeability (μr)
Silver 1.05 1.0
Copper 1.00 1.0
Aluminum 0.61 1.0
Steel (SAE 1010) 0.10 1,000

EMI Calculation Example

If you are using a 0.5 mm Copper shield at 100 MHz:

  • Start Frequency: 100 MHz
  • Conductivity: 1.0
  • Permeability: 1.0
  • Calculated Absorption: ~6.57 dB
  • Calculated Reflection: ~148.00 dB
  • Total Effectiveness: ~154.57 dB

Note that for most commercial applications, a Shielding Effectiveness of 30-60 dB is considered good, while 60-90 dB is excellent for high-precision laboratory or military hardware.

function calculateEMITable() { var startF = parseFloat(document.getElementById('startFreq').value); var thick = parseFloat(document.getElementById('thickness').value); var sigR = parseFloat(document.getElementById('conductivity').value); var muR = parseFloat(document.getElementById('permeability').value); var tableBody = document.getElementById('emiTableBody'); var resultSection = document.getElementById('emiResultSection'); var summaryDiv = document.getElementById('emiSummary'); if (isNaN(startF) || isNaN(thick) || isNaN(sigR) || isNaN(muR) || startF <= 0) { alert("Please enter valid positive numerical values for all fields."); return; } tableBody.innerHTML = ""; resultSection.style.display = "block"; var frequencies = [startF, startF * 2, startF * 5, startF * 10, startF * 20, startF * 50, startF * 100, startF * 500, startF * 1000, startF * 5000]; var maxSE = 0; var maxFreq = 0; for (var i = 0; i maxSE) { maxSE = totalSE; maxFreq = f; } var row = document.createElement('tr'); row.innerHTML = '' + f.toLocaleString() + ' MHz' + '' + absorption.toFixed(2) + ' dB' + '' + reflection.toFixed(2) + ' dB' + '' + totalSE.toFixed(2) + ' dB'; tableBody.appendChild(row); } summaryDiv.innerHTML = "Engineering Summary: At a thickness of " + thick + " mm, your material provides a peak shielding effectiveness of " + maxSE.toFixed(2) + " dB within the calculated range. Note that Reflection Loss decreases as frequency increases, while Absorption Loss increases with the square root of frequency."; }

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