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Wireless & Mobility · Foundational

Decibel-Milliwatt (dBm)

Absolute power level in decibels relative to 1 milliwatt (0 dBm = 1 mW).

Definition

dBm expresses absolute power on a logarithmic scale with 1 mW as the reference. Positive values exceed 1 mW and negative values are fractions of a milliwatt, which is typical of received signals. Transmit powers, receive sensitivity, and noise floors are all expressed in dBm.

Example

20 dBm = 100 mW, 30 dBm = 1 W, and -70 dBm = 0.0000001 mW.

Exam tip

A received signal of -65 dBm is stronger than -75 dBm; values closer to zero are stronger.

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