HP 8163A - Page 65

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:
Where,
P
dBm
is the power value displayed in dBm, and
P
input
is the input signal level in Watts.
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
dB
is the power value displayed in dB,
P
input
is the input signal level in Watts, and
P
ref
is the chosen reference power value in Watts.
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.
P
dBm
10
P
input
W()
110
3–
W()×
-------------------------------log=
P
dB
10
P
input
W()
P
ref
W()
-------------------------log=