Shielding Effectiveness of Enclosures:Characterising the Transition from Reverberant to Resonant Behavior

Understanding the shielding effectiveness (SE) of enclosures across different frequency ranges is crucial for electromagnetic compatibility (EMC) applications. While well-established methods exist for evaluating SE in the reverberant frequency range, the transition between reverberant and resonant behavior remains less explored. This paper investigates the shielding performance of a brass enclosure containing Transmission Line Representative Contents (TL ReCos) across the reverberant, transition, and resonant frequency regions. The study employs a mechanically stirred reverberation chamber (RC) to analyze the SE response using a combination of wall-mounted and internal monopole antennas. Results confirm the existence of a transition frequency region with change in field distribution and SE behavior. The findings highlight how variations in frequency, internal contents, and measurement positions influence SE, providing valuable insights for enclosure design and EMC testing.