What difference between peak-power, average power and true RMS power in RF measurement? I have read a peak-power measurement can calculate average power measurement also. Does any of these needs signal to be demodulated?
These are detectors, or aggregation functions during a sweep.
Your analyzer allows you to set up a number of sweep points across the spectrum. The sweep time is divided by the number of sweep points, and this time is integrated into a single point.
- The "max peak" detector uses the highest value during the sweep point interval
- The "average" detector averages the magnitude
- The "RMS" detector averages the power (proportional to magnitude squared).
If you have a fairly coarse grid (few points), you can get visible peaks using the max peak detector, which allows you to find the signal quickly, but the power displayed will be too large, while the RMS and average detectors would report values that are too small:
With a finer grid, all three detectors report values close to the actual power for a CW signal, because now they only differ in how the noise is integrated:
However, for a modulated signal (pulse, 8 us off, 2 us on) you can clearly see the difference (note that I used a long sweep time here):