Terms like dBW and dBm are widely used within radio frequency engineering as the measure of power.
The power levels expressed in dBm or dBW may not always be as meaningful as power expressed in watts and therefore a simple conversion chart converting dBm to watts and dBW and vice versa can be very useful.
Many power levels themselves for power meters, spectrum analysers, signal generators are specified in dBm or dBW rather than watts. Also RF components such as mixers, oscillators and the like, as well as the interfaces between modules in RF equipment have their levels specified in dBm or dBW. Radio transmitters may also have their output levels expressed in terms of dBW.
dBm and dBW - the basics
A decibel is not an absolute level - it is a comparison between two levels, and on its own it cannot be used to measure an absolute level. As a result of this the quantities of dBm and dBW are used:
- dBm - This is a power expressed in decibels relative to one milliwatt.
- dBW - This is a power expressed in decibels relative to one watt.
From this it can be seen that a level of 10 dBm is ten dB above one milliwatt, i.e. 10 mW. Similarly a power level of 20 dBW is 100 times that of one watt, i.e. 100 watts.
A more extensive conversion chart of dBm, to dBW and to watts is given below:
dBm to dBW & watts chart
The chart below gives a tabulation of dBm to dBW and watts which can be useful in determining some quick rough estimates of the values of power in different formats.
|dBm to dBW & Watts Conversion Chart|
|+100||+70||10 000 000||10 Megawatts|
|+90||+60||1 000 000||1 Megawatt|
|+80||+50||100 000||100 kilowatts|
|+70||+40||10 000||10 kilowatts|
|+60||+30||1 000||1 kilowatt|
With use the terms dBm, and dBW come to have their meaning and mentally it is possible to convert between them. However it is always useful to have a conversion table or chart to hand to be able to convert one to another.