Average Detector
Comparison
| Parameter | Typical | High-Perf | Unit | Notes |
|---|---|---|---|---|
| Frequency | Standard | Extended | GHz | Band-dependent |
| Performance | Nominal | Optimized | dB | Application-specific |
| Linearity | Moderate | High | dBc | System requirement |
| Integration | Discrete | Monolithic | — | Cost vs performance |
| Cost | Low | Premium | $ | Volume-dependent |
Understanding Average Detector
V_avg = (1/T) x integral(0 to T) |V(t)| dt (linear average)
P_avg = (1/T) x integral(0 to T) |V(t)|^2 dt (RMS/power average)
For CW signals: V_avg = V_peak (same as peak detector)
For pulsed signals: V_avg = V_peak x duty_cycle (much lower than peak)
Frequently Asked Questions
When do you use average vs. peak detector?
Peak detector captures the worst-case instantaneous amplitude, used for interference potential assessment. Average detector measures the continuous power content, more relevant for receiver desensitization. CISPR standards require both measurements, each compared against its own limit line.
What is the difference between average and quasi-peak detectors?
The quasi-peak (QP) detector is a weighted peak detector with specific charge and discharge time constants defined by CISPR 16. QP readings fall between peak and average for pulsed signals. QP was designed to correlate with human perception of interference annoyance in AM radio receivers.
Why does CISPR require three different detectors?
Each detector captures a different aspect of the emission. Peak shows worst-case amplitude (protects digital receivers). Average shows continuous power (protects analog receivers from desensitization). Quasi-peak provides a weighted metric that correlates with subjective interference annoyance. All three must pass their respective limits.