An Efficient Modeling Approach for Quiet Zone Estimation of Anechoic Chambers using Planer Equivalence of RF Absorbers

The accurate estimation of quiet zones in anechoic chambers is critical for electromagnetic compatibility testing. Waveguide testing of absorbers limits the reflectivity measurement to normal incidence, while full-wave simulations of pyramidal absorbers are computationally intensive and impractical for large chambers. This paper introduces a novel, efficient modeling approach that overcomes these challenges by combining full-wave simulations with a Quasi-Newton optimization method to extract the relative permittivity and angular-dependent reflectivity of absorbers. By replacing complex pyramidal structures with planar equivalents via Fresnel Boundaries, the proposed method achieves over 95% reduction in simulation time while maintaining high accuracy (errors in field distribution < 3dB). Validation is performed against traditional simulations and experimental data, proving the proposed approach enables rapid evaluation of quiet zones at 1 GHz and demonstrates good agreement in reflection levels. The proposed modeling approach offers practical value for instances requiring fast, reliable performance assessments of RF absorbers and anechoic chambers.