What Is the RF Shielding Effectiveness Calculator (Schelkunoff Wave Theory)?
Shielding Effectiveness (SE) measures the reduction in electromagnetic field strength (in decibels) achieved by placing a barrier between an RF noise source and a receiver.
Schelkunoff’s transmission line theory models electromagnetic wave propagation through conductors as wave reflection at mismatched boundary interfaces plus bulk absorption.
How Does the RF Shielding Effectiveness Calculator (Schelkunoff Wave Theory) Work?
Reflection Loss (R) arises from the massive impedance mismatch between the wave (377 Ω for far-field plane waves) and the high conductivity metal surface (~0.01 Ω).
Absorption Loss (A) occurs as eddy currents dissipate wave energy into heat via skin depth attenuation.
Multiple reflection correction (B) accounts for waves reflecting back and forth between the front and back surfaces of very thin shields.
RF Shielding Effectiveness Calculator (Schelkunoff Wave Theory) Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Applies Schelkunoff transmission line analogy: total shielding equals reflection loss plus absorption loss plus multiple reflection re-radiation factor.
How to Use the RF Shielding Effectiveness Calculator (Schelkunoff Wave Theory)
- Specify the frequency and choose the field type (plane wave, near electric, or near magnetic).
- Enter shield thickness and material properties (conductivity and permeability).
- Evaluate whether total SE meets regulatory standards (e.g. 60–80 dB for industrial EMC, 100+ dB for MIL-STD).
Step-by-Step Example Calculation
1 mm Aluminum Shield at 100 MHz Plane Wave
Input Values:
Understanding Your Result
SE of 20 dB = 90% field reduction; 40 dB = 99%; 60 dB = 99.9%; 100 dB = 99.999%.
Low-frequency magnetic fields are the hardest to shield because reflection loss is small.
Factors That Affect the Result
- Permeability (μr): High permeability (steel, mu-metal) dramatically increases absorption loss for low-frequency magnetic fields.
- Seams and apertures: Real enclosures leak predominantly through slots, gaskets, and cable penetrations rather than bulk metal penetration.
When Should You Use This Calculator?
- Designing electronic chassis for FCC/CE EMC compliance.
- Developing RF shielded rooms, MRI scan enclosures, and Tempest security chambers.
Assumptions & Limitations
- Assumes continuous, unpunctured sheet metal without vents, slots, or seams.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Classical Schelkunoff formulation accurate to within ±2 dB for solid continuous sheets.