Calculating Equivalent Power - Agilent Technologies 85024A User's And Service Manual

16. Connect the probe, the probe adapter, and a barrel between the attenuator and the power sensor. The
signal from the analyzer should now go through the attenuator and then the probe before reaching the
power sensor. Record the power reading on the
17. Remove the attenuator pad, connect the probe adapter to the output port of the analyzer. Connect the
attenuator pad between the probe and the power sensor. The signal from the analyzer should now go
through the probe and then the pad before reaching the power sensor. Record the power reading on
the "Test Record" on page 5-9
18. Perform the calculation indicated on the test record to determine the result of the test.

Calculating Equivalent Power

The probe is usually used as a high impedance device. The compression specification is given as a
voltage (instead of power) because of the wide range of devices with which the probe may be used. For
testing the probe, the probe adapter is used to make the probe input 50 . Using this known impedance,
an equivalent power can be calculated.
To find the power level equivalent to the 0.3 peak voltage, perform the following mathematical steps:
Steps
1. Convert the peak voltage into RMS.
2. Convert the RMS voltage to a raw power.
3. Convert the raw power to a power
which is relative to 1 mW. 
4. Convert to dBm. 
* Therefore, as shown in the example, the equivalent power to 0.3 V peak in a 50 system is 0.458
dBm.
Chapter 5
"Test Record" on page 5-9
(item G).
Formula
V
pk
------------------------ -
1.4142135
2
V
----- -
R
divide by 0.001w

10 LOGx
(item F).
Example
0.3V
------------------------ - =
1.4142135
2
 
0.212132
----------------------------- =
50
0.009w
----------------- = 0.9
0.001w

 
10 LOG 0.9
Performance Tests
Gain Compression
0.212132V
RMS
0.0009w
*
= –
0.458 dBm
5-7