Reverberation Chambers
Reverberation chambers represent a fundamentally different approach to EMC testing compared to traditional anechoic facilities. Instead of creating a controlled, reflection-free environment, reverberation chambers deliberately exploit multiple reflections from metallic walls to generate a statistically uniform electromagnetic field throughout the test volume. This statistical approach offers unique advantages for certain types of EMC measurements, including immunity testing, emissions testing, and shielding effectiveness evaluation.
The underlying principle of reverberation chamber operation relies on creating an overmoded cavity where many resonant modes exist simultaneously at the test frequency. By mechanically or electronically stirring these modes, the chamber produces a field that, when averaged over time or stirrer positions, exhibits statistical uniformity and isotropy. This means the equipment under test is exposed to fields arriving from all directions with all polarizations, providing a thorough test of immunity without requiring multiple equipment orientations.
Articles
Reverberation Chamber Theory
Master statistical field environments. This section addresses mode density, field uniformity, statistical properties, Q factor, loading effects, frequency limitations, stirring mechanisms, chamber calibration, and correlation functions.
Chamber Design and Construction
Build effective test environments. Topics include chamber sizing, stirrer design, antenna placement, sample positioning, shielding effectiveness, door design, penetrations, instrumentation, and safety features.
Measurement Procedures
Perform valid reverberation testing. Coverage encompasses stirring sequences, sample loading, field uniformity validation, statistical analysis, measurement uncertainty, absorption cross-section, shielding effectiveness testing, radiated immunity testing, and emissions testing.
Applications and Limitations
Apply reverberation techniques appropriately. This section covers applicable frequency ranges, sample size limitations, directivity information, comparison with anechoic methods, cost benefits, throughput advantages, statistical interpretation, standards compliance, and hybrid techniques.
About This Category
Reverberation chambers have evolved from research curiosities to mainstream EMC test facilities over the past several decades. They are now recognized by major standards organizations including IEC, CISPR, and various military standards as valid alternatives to anechoic chambers for many EMC tests. Understanding when and how to use reverberation chambers, along with their theoretical foundations and practical limitations, enables EMC engineers to select the most appropriate test methodology for their specific requirements while potentially reducing test time and facility costs.