## RF Power Levels – dBm and dBW

**dBm and dBW are widely used to measure absolute power levels in RF engineering**

The ratio of two RF power (or voltage) levels can be expressed in dB. This is a dimensionless quantity and does not provide any information about the actual (or absolute) power levels involved, only the relative levels. A more useful way of comparing power (or voltage) levels is to reference them to a standard power level.

For low-power systems, such as those used in mobile communications, the dBm (decibel-milliwatt) scale is a convenient reference power level, in which power is referenced to a level of 1 mW:

\(P \:(dBm) = 10\log\bigg(\displaystyle \frac{P\:(mW)}{1\:mW}\bigg)\)

For high-power systems, such as those used in satellite communications, the dBW (decibel-watt) scale is commonly used, in which power is referenced to 1 W:

\(P \:(dBW) = 10\log\bigg(\displaystyle \frac{P\:(W)}{1\:W}\bigg)\)

Therefore, a power level of 10 W (or 10,000 mW), is expressed as +40 dBm when referenced to 1 mW or +10 dBW when referenced to 1 W.

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