Improvement of Field Uniformity Evaluation in Reverberation Chambers: A Simulation-Based Analysis of EUT Volume and Uniform Region Proportion

Reverberation chambers are essential facilities for electromagnetic compatibility testing, and their internal field uniformity critically determines the accuracy of test results. The current IEC 61000-4-21 standard primarily restricts the size of the Equipment Under Test (EUT) based on its physical volume, recommending it not exceed 8% of the total RC volume. However, this empirical guideline overlooks critical factors such as the EUT's electrical size and geometric shape, leading to significant limitations. This paper employs both the Plane Wave Superposition (PWS) method and full-wave Multi-Level Fast Multipole Method (MLFMM) simulations to systematically investigate the impact of various EUT types on field uniformity. Our findings reveal that an EUT's electrical size and shape are often dominant factors in perturbing the field uniformity, demonstrating that the physical volume ratio criterion alone is insufficient for ensuring test validity. Simulation results show that some EUTs compliant with the 8% rule still cause excessive field degradation, while some larger EUTs do not. The comparison between simulation methods also highlights that full-wave simulations, which capture the complete EUT-cavity coupling, are essential for accurately assessing the actual loading effect. This research provides in-depth analysis and a comprehensive simulation dataset that challenge the adequacy of the current standard.