Conference Agenda

This study focuses on the uncertainty estimation in magnetic field shielding effectiveness measurements performed in the time domain. The measurement method is inspired by the standard IEEE 299, and the target frequency range is from 150 kHz to 30 MHz. First, we identify the most significant sources of error. Those uncertainty contributions are considered in a model for the measurement system. This model is used to classify and quantify the sources of uncertainty independently. The relevant uncertainty sources are the measuring instrument accuracy, signal generator stability, preamplifier gain, antenna position variability, repeatability due to the influence of the setup, and proximity to the noise floor, the latter being the most significant. The measurement uncertainty, including systematic and random effects, is estimated at 1.9 dB, for shielding effectiveness below 60 dB and up to 11.7 dB when the detection becomes challenging. The results confirm the importance of maximizing the dynamic range achievable with the proposed measurement system through the optimal excitation signals.

This paper investigates the validity of the Schelkunoff Transmission-Line model (using the concept of wave impedance) for assessing the shielding effectiveness of infinitely large planar materials in a two-parallel loops configuration under near-field conditions. The validity of the Schelkunoff's model is evaluated by comparing it with two infinite integral-based solutions: one excluding the receiving loop antenna and the other including it, as well as with numerical simulations. Numerical simulations were conducted using a low-frequency finite-element-method solver, covering frequencies from 9 kHz to 10 MHz. Results indicate that when the loop-to-loop distance exceeds the radii of the loops, all models show good agreement. However, discrepancies arise when this condition is not met, casting doubt on the suitability of employing the Schelkunoff transmission-line model with the corresponding wave impedance approach in such cases.

This paper investigates the impact of the individual board level shield walls on its shielding effectiveness under near-field conditions. Utilizing 3D full-wave simulations with the Finite-Difference Time-Domain solver, the study covers a frequency range from 10 MHz to 10 GHz. A 50 Ω terminated microstrip is used as an on-board source, and the board level shield is characterized using the adapted SAE ARP 6248 stripline method. The study underscores techniques for connecting the board level shield to the printed circuit board's ground plane while analyzing leakage contributions from the different walls of the board level shield. Various scenarios with varying conductivity were gauged to understand leakage mechanisms. Notably, this study clarifies that the top side of the board level shield is the primary source of leakage and a dominant factor in overall shielding performance.

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.