R3267 Series Spectrum Analyzer Operation Manual (Vol.1)
A.4 dB Conversion Formulas
A-16
A.4
dB Conversion Formulas
Definitions
0dBV = 1Vrms
YdBV = 20log
0dBm = 1mW
YdBm = 10log
0dB
µ
V = 1
µ
Vrms
YdB
µ
V = 20log
0dBpw = 1pW
YdBpw = 10log
Conversion formulas
If R = 50
Ω
:
If R = 75
Ω
:
dBV
≅
(dBm - 13dB)
dBV
≅
(dBm - 11dB)
dB
µ
V
≅
(dBm + 107dB)
dB
µ
V
≅
(dBm + 109dB)
dB
µ
Vemf
≅
(dBm + 113dB)
dB
µ
Vemf
≅
(dBm + 115dB)
dBpw
≅
(dBm + 90dB)
dBpw
≅
(dBm + 90dB)
Examples
Converting 1mV into dB
µ
V:
20log
= 20log 10
3
= 60dB
µ
V
Converting 0dBm into dB
µ
V:
0dBm + 107dB = 107dB
µ
V(R = 50
Ω
)
0dBm + 109dB = 109dB
µ
V(R = 75
Ω
)
Converting 60dB
µ
V into dBm:
60dB
µ
V - 107dB = -47dBm(R = 50
Ω
)
60dB
µ
V - 109dB = -49dBm(R = 75
Ω
)
Converting 10V/m into dB
µ
V/m:
20log
= 140dB
µ
V/m
Relationship between dBm and Watt
+50dBm
+40dBm
+30dBm
+20dBm
+10dBm
+0dBm
-10dBm
-20dBm
-30dBm
100W
10W
1W
100mW
10mW
1mW
0.1mW
0.01mW
0.001mW
XV
1V
1mW
XmW
1
µ
V
X
µ
V
XpW
1pW
1mV
1
µ
V
{
{
10V/m
1
µ
V/m