How To Set The Power Unit; What Are The Power Units - Agilent Technologies 8163A User Manual

Power Measurement
80

How to Set the Power Unit

Pressing the Power Unit softkey allows you to select either W, dB, or
dBm as the units in which power is displayed. The Power Unit softkey
is visible when you move to the [P] or [Ref ] parameters. Alternatively
the Power Unit can be changed by using the Power Meter menu.

What are the Power Units ?

Watts (W) are the SI unit for power measurement.
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 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. For information on selecting this reference value, see
"How to Input a Reference Level" on page 82.
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 42.
Agilent 8163A/B, 8164A/B, and 8166A/B User's Guide, Fourth Edition
( )
P W
input
P = 10 log ----------------------------- -
dBm
3 –
× ( )
1 10 W
( )
P W
i nput
P = 10 log ------------------------ -
dB ( )
P W
ref
How to Measure Power