Agilent Technologies PSA Series Manual page 284

Concepts
RF Power Measurement Concepts
RF Power Measurement Concepts
Purpose
RF Power quantifies the output level, in an absolute term, of a signal generator or
an attenuator being calibrated. This is a common measurement for broadband
RF/microwave signals.
The RF Power Measurement is used to accurately measure the RMS RF power of
the signal by using the power meter with a sensor module. Absolute level accuracy
and sensitivity are determined by the particular power sensor selected and the
SWR (Standing Wave Ratio) of the signal source.
Measurement Technique
RF Power measurements uses an external power meter with a sensor module to
measure the RMS power of the RF input signal. The frequency of the RF input
signal is automatically measured by the Frequency Counter measurement, then the
appropriate Cal Factor is obtained from the stored Cal Factor File and
automatically applied to the power meter data.
The corrected power measurement data is then converted to the units selected and
final result is displayed on the PSA or your PC monitor. When using the IVI-COM
API or SCPI commands, the result is available for remote query.
The calibration procedure allows the system to set the power-measurement transfer
function so the displayed power correctly represents the actual power. This
procedure can be visualized as a process that adjusts the intercept and slope of the
sensor's transfer function. The displayed power is given by the equation:
Equation 5-1
where:
P
P
b = zero crossing, and
m = slope.
The calibration routine forces b = 0 and m = 1.
The following example shows the different responses that occur during calibration:
284
P = mP
dis
= Displayed Power,
dis
= Actual Power,
act
+ b
act
Chapter 5