All-Metal Coding Metasurface Stirrers for Next Generation Reverberation Chambers: Breaking Lowest Usable Frequency and Working Volume Limitations

The evolution of electromagnetic compatibility (EMC) standards demands reverberation chambers (RCs) with superior field uniformi-ty and spatial efficiency. While metasurface-based stirrers are emerging as compact alternatives to traditional Z-shaped mechanical stirrers, their metal-dielectric-metal architectures suffer from dielectric-induced Q-factor degradation (typically < 10³) and inefficient low frequency mode stirring. Here, we present a paradigm-shifting all-metal coding metasurface stirrer (CMSS) that synergizes Pan-charatnam-Berry phase modulation with stochastic coding optimization. This innovation achieves threefold metrics: (1) Lowest usable frequency (LUF) suppression via optimized coding sequences; (2) Working volume (WV) expansion through low-profile CMSS de-sign; (3) Q-factors sustainment with dielectric-free CMSSs. Experimental validation using three CMSS units in a 1.2 m × 0.8 m × 1.2 m aluminum chamber demonstrates 11.2% LUF reduction, 78.9% WV expansion and 10³~10⁴ Q-factor sustainment. These breakthroughs position CMSS as a cornerstone technology for 5G FR1 (410~7125MHz) and automotive EMC testing (ISO 11452-4), enabling more efficient, compact, multi-standard compliant RCs for advanced EMC testing.