Purpose: To create a Faraday cage that minimizes electromagnetic interference (EMI) for biomedical signal measurements.
Key Topics:
Electromagnetic field mapping (EFM)
Current density analysis
Simulation methods and results
Definition: An electromagnetic enclosure designed to shield internal electric fields from external influences.
Main Functions:
Maintains a zero internal electromagnetic field with applied non-zero charge.
Protects biomedical measurements from environmental noise (e.g., from electromechanical devices and wireless communications).
Serves a dual role in shielding electronic devices and in testing for electromagnetic compatibility (EMC).
Design Characteristics:
Target frequency: 206 MHz.
Design utilizes a mapping approach to determine sources of EMI and dimension the cage appropriately.
Electromagnetic Field Mapping (EFM):
Measurement performed using a Biconical antenna and Spectrum Analyzer.
The area divided into quadrants; data collected for areas with significant electric fields.
Identification of problematic wavelengths is fundamental to the design.
Software Utilized: COMSOL Multiphysics for finite element method (FEM) simulations.
Simulation Set-up:
Developed a 4m x 4m x 3m enclosure with specific dielectric properties.
Two scenarios simulated: with and without absorbent materials.
Anechoic Chamber Simulation:
Designed to reflect an ideal space free from waves and interference; no reflections occur.
Physical parameters adjusted to model the absorption of electromagnetic waves.
Simulation Outcomes:
Reduced current density and distortion in the presence of absorbents during simulations.
Effective shielding at 206 MHz measured at approximately 181 dB.
Field Patterns:
Uniform electric field observed, allowing for effective biomedical measurements.
Areas of low intensity indicate optimal spots for capturing biopotential signals.
Implications: Successful design of Faraday cage enhances the quality of biomedical measurements by reducing signal distortion from EMI.
Future Considerations:
Additional parameters such as living organism regulation and monitoring windows must be incorporated into the cage design.