Design of a faraday cage for biomedical measurements

Overview of Faraday Cage Design for Biomedical Measurements

• 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

Faraday Cage Functionality

• 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 and Methodology

• 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.

Simulation Processes

• 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.

Results and Findings

• 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.

Conclusion

• 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.