Keysight Technologies 33210A - Page 357

Tutorial 7
Keysight 33210A User’s Guide 357
You may occasionally see ac levels specified in “decibels relative to 1 milliwatt”
(dBm). Since dBm represents a power level, you will need to know the signal’s
RMS voltage and the load resistance in order to make the calculation.
dBm = 10 × log
10
(P / 0.001) where P = V
RMS
2
/ R
L
For a sine wave into a 50Ω load, the following table relates dBm to voltage.
For 75
Ω or 600 Ω loads, use the following conversions.
dBm (75
Ω ) = dBm (50 Ω ) – 1.76
dBm (600
Ω ) = dBm (50 Ω ) – 10.79
NOTE
If an average-reading voltmeter is used to measure the “DC voltage” of a
waveform, the reading may not agree with the DC Offset setting of the function
generator. This is because the waveform may have a non-zero average value
that would be added to the DC Offset.
dBm RMS Voltage Peak-to-Peak Voltage
+23.98 dBm 3.54 Vrms 10.00 Vpp
+13.01 dBm 1.00 Vrms 2.828 Vpp
+10.00 dBm 707 mVrms 2.000 Vpp
+6.99 dBm 500 mVrms 1.414 Vpp
0.00 dBm 224 mVrms 632 mVpp
-6.99 dBm 100 mVrms 283 mVpp
-10.00 dBm 70.7 mVrms 200 mVpp
-36.02 dBm 3.54 mVrms 10.0 mVpp