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dBm or dB mW (decibel-milliwatts) is a unit of power level expressed using a logarithmic decibel (dB) scale respective to one milliwatt (mW). It is commonly used by radio, microwave and fiber-optical communication technicians & engineers to measure the power of system transmissions on a log scale , which can express both very large and very ...
A power level of 0 dBm corresponds to one milliwatt, and 1 dBm is one decibel greater (about 1.259 mW). In professional audio specifications, a popular unit is the dBu . This is relative to the root mean square voltage which delivers 1 mW (0 dBm) into a 600-ohm resistor, or √ 1 mW × 600 Ω ≈ 0.775 V RMS .
For very low-power systems, such as mobile phones, signal strength is usually expressed in dB-microvolts per metre (dBμV/m) or in decibels above a reference level of one milliwatt . In broadcasting terminology, 1 mV/m is 1000 μV/m or 60 dBμ (often written dBu). Examples. 100 dBμ or 100 mV/m: blanketing interference may occur on some receivers
The dBm is an absolute reference level measurement (see Decibel § Suffixes and reference values) with respect to 1 mW power. When the nominal signal power is 0 dBm at the TLP, the test point is called a zero transmission level point, or zero-dBm TLP. The abbreviation dBm0 stands for the power in dBm measured
dBm = 2 × ASU - 113, ASU in the range of 0.31 and 99 (for not known or not detectable). In UMTS networks, ASU maps to RSCP level (received signal code power, see TS 27.007 [3] sub clause 8.69 and TS 25.133 sub clause 9.1.1.3). dBm = ASU - 115, ASU in the range of 0.90 and 255 (for not known or not detectable).
A field level (or root-power level) is a logarithmic quantity used to measure quantities of which the square is typically proportional to power (for instance, the square of voltage is proportional to power by the inverse of the conductor's resistance), etc., with commonly used units neper (Np) or decibel (dB).
When the test impedance is 600 Ω resistive, 0 dBm can be referred to a voltage of 775 mV, which results in a reference active power of 1 mW. Then 0 dBm0 corresponds to an overload level of approximately 3 dBm in the analog-to-digital conversion. Given a sinusoid signal of 0.775 V RMS, the power at a zero transmission level point is:
−13 dBm biomed: sound power incident on a human eardrum at the threshold intensity for pain (500 mW/m 2). 10 −3: milli-(mW) 1.55 × 10 −3: −4.7 dBm astro: power per square meter received from the Sun by Sedna at its aphelion 5 × 10 −3: 7 dBm tech: laser in a CD-ROM drive 5–10 × 10 −3: 7 dBm to 10 dBm tech: laser in a DVD player ...