Input power in dBm and conversion to Vrms

[ccw27]

dbm to vrms

Given input power in dBm, we can convert to mW by 10^(dBm/10). However we can't use 10^(dBm/20)*1E-3 to convert to Vrms, right? But if we are doing a calculation that involves a ratio of two voltages then its ok to use the above expression without taking load into account, right? The formula I want to use is LO leakage = 20log(2*Vdc/Vm) and I want to compute Vm from input power given.

Thanks

 

[brmadhukar]

dbm vrms convert

Hi,
dB is always used for power ratio. To convert it any other form use the formula for the power
P = VI = I*I*R = V*V/R
and use it. It is straigh forward.

B R
M

 

[dainis]

vrms to dbm

CATV dBm, dBmV, and dBµV Conversions
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http://www.scte.org.uk/members/technical/conversions.html
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[selvaraja]

Re: dBm, Vrms confusion

PdBm=10log(Pwatt/1mW)

Pwatt= vrms²/R