HP 8163A User Manual page 65

Power Measurement
How to Measure Power
You can also measure power in dB or dBm. Values displayed in
these units are derived from measurement in Watts.
By selecting dBm, the following calculation is made:
P
Where,
P is the power value displayed in dBm, and
dBm
P is the input signal level in Watts.
input
Power, in units of dBm, is measured relative to 1 mW, it is an
absolute power measurement.
By selecting dB, the following calculation is made:
Where,
P is the power value displayed in dB,
dB
P is the input signal level in Watts, and
input
P is the chosen reference power value in Watts.
ref
Power, in units of dB, is measured relative to a particular reference
power value. You must select this reference value.
To set the power unit to dBm:
1 Move to the [P] parameter and press the [Power Unit] softkey.
You will see the menu in Figure 3-2.
65
( )
P W
input
= 10 log ------------------------------ -
dBm
3 –
× ( )
1 10 W
( )
P W
input
P = 10 log ------------------------ -
( )
dB
P W
ref