What is the reverberation chamber technique for EMC testing and how does it compare to an anechoic chamber?
Reverberation Chamber EMC Testing
Reverberation chambers have become increasingly important for EMC testing, particularly for immunity testing (IEC 61000-4-21), radiated emissions testing, wireless device testing, and shielding effectiveness measurement. They offer significant cost, size, and time advantages over anechoic chambers for many applications.
| Parameter | SOLT Cal | TRL Cal | eCal |
|---|---|---|---|
| Accuracy | Good | Excellent | Good-very good |
| Standards Needed | 4 (S,O,L,T) | 3 (T,R,L) | 1 (module) |
| Bandwidth | Broadband | Band-limited | Broadband |
| Setup Time | 5-10 min | 10-20 min | 1-2 min |
| Best For | Coaxial, general | On-wafer, waveguide | Production, speed |
Calibration Procedure
When evaluating the reverberation chamber technique for emc testing and how does it compare to an anechoic chamber?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.
Error Sources
When evaluating the reverberation chamber technique for emc testing and how does it compare to an anechoic chamber?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Fixture Considerations
When evaluating the reverberation chamber technique for emc testing and how does it compare to an anechoic chamber?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.
Frequently Asked Questions
Can I use a reverberation chamber for emissions testing?
Yes. For radiated emissions: the EUT emits radiation inside the chamber, and a receive antenna measures the total radiated power (TRP). The relationship between the emitted power and the received power is: P_received = P_emitted × lambda^2 / (16 pi^2 × V × (delta_f/f)) where delta_f is the chamber decay time. The TRP can be converted to equivalent far-field emissions. IEC 61000-4-21 Annex D describes the procedure. Advantages: the total emitted power from all directions is captured in a single measurement (no angular scan needed).
How does field uniformity compare to an anechoic chamber?
Anechoic chamber: the field is deterministic and uniform within the quiet zone (typically ±1-2 dB). The direction and polarization are known and controlled. Reverberation chamber: the instantaneous field is highly non-uniform (with hot and cold spots). But the statistical average (over stirrer positions) is uniform to within ±3-6 dB throughout the working volume. The standard deviation decreases as more stirrer samples are averaged. IEC 61000-4-21 requires the field uniformity standard deviation to be < 3 dB for valid testing.
What is the cost comparison?
Reverberation chamber: a 3×4×5 m chamber costs approximately $100,000-$300,000 (shielded room + stirrer + antenna). Anechoic chamber: a similar-sized semi-anechoic chamber costs approximately $300,000-$1,000,000 (shielded room + absorber costing $100,000-$500,000). The reverberation chamber is typically 30-50% less expensive and requires less physical space (no absorber bulk). Testing time: reverberation chamber testing is also faster (one measurement covers all angles and polarizations).