Agilent Technologies PSA Series Manual page 288

Concepts
Tuned RF Level Measurement Concepts
Second RF Input Ranging Calibration
When the power level of the input signal is lowered to the 3rd range (which varies
by different frequency band in the PSA), the Measuring Receiver creates a third
calibration factor (as CF3, Cal Factor for Range3) by comparing the power level
measured before and after the range changes. The input signal level must not
change during this recalibration. This new calibration factor CF3 is multiplied by
the calibration factor CF2, and C1made previously (with the reference) to be used
in all subsequent measurements in RF range3 at that frequency.
Calibrating the Calibrated Level
From above, two Cal factors can be obtained for three ranges, range1, range2 and
range3 as CF1, CF2 and CF3 (linear unit instead of dB). If let P1, P2 and P3 (linear
unit instead of dBm) be the levels for range1,range2 and range3 from PSA
separately, the P is the actual power, we have:
P = P1 * CF1, If P1 is in range1
P = P2 * CF1* CF2, If P2 is in range2
P = P3* CF1*CF2* CF3, If P3 is in range3
Figure 5-3 TRFL Ranging Calibration
288 Chapter 5