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 uniformity and high 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 less than$10^{3}$) and inefficient low-frequency mode stirring. Here, we present a paradigm-shifting all-metal coding metasurface stirrer (CMSS) that synergizes Pancharatnam-Berry phase modulation with stochastic coding optimization. This innovation achieves three-fold metrics: reduction of the lowest usable frequency (LUF) through optimized coding sequences; expansion of the working volume (WV) via a low-profile CMSS design; and sustainment of Q-factors with dielectric-free CMSSs. Experimental validation using three CMSS units in a$1.2\ \mathrm{m}\times 0.8\ \mathrm{m}\times 1.2\ \mathrm{m}$aluminum chamber demonstrates an 11.2% LUF reduction, a 78.9% WV expansion, and the sustainment of Q-factor of$10^{3}-10^{4}$. These breakthroughs position CMSS as a cornerstone technology for 5G New Radio Frequency Range 1 (410–7125 MHz) and automotive EMC testing (ISO 11452–4), enabling more efficient, compact, multi-standard compliant RCs for advanced EMC testing.