- Source: DBm
- Source: DBM
dBm or dBmW (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 small values in a short form. dBW is a similar unit measured relative to one watt (1,000 mW), rather than a milliwatt.
The decibel (dB) is a dimensionless unit, used for quantifying the ratio between two values, such as signal-to-noise ratio. The dBm is also dimensionless, but since it compares to a fixed reference value, the dBm rating is an absolute one.
The dBm is not a part of the International System of Units (SI) and therefore is discouraged from use in documents or systems that adhere to SI units. (The corresponding SI unit is the watt.) However, the unit decibel (dB), without the 'm' suffix, is permitted for relative quantities, but not accepted for use directly alongside SI units. Ten decibel-milliwatts may be written 10 dB (1 mW) in SI.: 7.4
In audio and telephony, dBm is typically referenced relative to the 600-ohm impedance commonly used in telephone voice networks, while in radio-frequency work dBm is typically referenced relative to a 50-ohm impedance.
Unit conversions
A power level of 0 dBm corresponds to a power of 1 milliwatt. A 10 dB increase in level is equivalent to a ten-fold increase in power. Therefore, a 20 dB increase in level is equivalent to a 100-fold increase in power. A 3 dB increase in level is approximately equivalent to doubling the power, which means that a level of 3 dBm corresponds roughly to a power of 2 mW. Similarly, for each 3 dB decrease in level, the power is reduced by about one half, making −3 dBm correspond to a power of about 0.5 mW.
To express an arbitrary power P in mW as x in dBm, the following expression may be used:
x
=
10
log
10
P
1
mW
{\displaystyle {\begin{aligned}x&=10\log _{10}{\frac {P}{1~{\text{mW}}}}\end{aligned}}}
Conversely, to express an arbitrary power level x in dBm, as P in mW:
P
=
1
mW
⋅
10
x
10
{\displaystyle {\begin{aligned}P&=1~{\text{mW}}\cdot 10^{\frac {x}{10}}\end{aligned}}}
Table of examples
Below is a table summarizing useful cases:
Standards
The signal intensity (power per unit area) can be converted to received signal power by multiplying by the square of the wavelength and dividing by 4π (see Free-space path loss).
In United States Department of Defense practice, unweighted measurement is normally understood, applicable to a certain bandwidth, which must be stated or implied.
In European practice, psophometric weighting may be, as indicated by context, equivalent to dBm0p, which is preferred.
In audio, 0 dBm often corresponds to approximately 0.775 volts, since 0.775 V dissipates 1 mW in a 600 Ω load. The corresponding voltage level is 0 dBu, without the 600 Ω restriction. Conversely, for RF situations with a 50 Ω load, 0 dBm corresponds to approximately 0.224 volts, since 0.224 V dissipates 1 mW in a 50 Ω load.
In general the relationship between the power level P in dBm and the RMS voltage V in volts across a load of resistance R (typically used to terminate a transmission line with impedance Z) is:
V
=
R
10
P
/
10
1000
.
{\displaystyle {\begin{aligned}V&={\sqrt {R{\frac {10^{P/10}}{1000}}}}\,.\end{aligned}}}
Expression in dBm is typically used for optical and electrical power measurements, not for other types of power (such as thermal). A listing by power levels in watts is available that includes a variety of examples not necessarily related to electrical or optical power.
The dBm was first proposed as an industry standard in the paper "A New Standard Volume Indicator and Reference Level".
See also
Decibel
Decibel watt
dBm0
References
This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).
External links
The dBm calculator for impedance matching
Convert dBm to watts
Science and technology
dBm, a unit for power measurement
DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB
Database Manager (DBM), a component of 1987's Extended Edition v1.0 release of IBM's OS/2 operating system
Dibenzoylmethane, an aromatic diketone: 1,3-diphenylpropane-1,3-dione
Dibromomethane, a halomethane
Difference bound matrix, a data structure used in a field of computer science
Dibutyl maleate, an organic chemical compound
Other uses
Debre Marqos Airport, IATA airport code is DBM
D. B. M. Patnaik (1925–2009), Indian lawyer, politician and communist leader
De Bellis Multitudinis, a wargame ruleset
Department of Budget and Management, the executive department in the Philippines
Development Bank of Mongolia, bank of Mongolia
D-flat minor, a theoretical musical key
Dynamic Business Modeling, the ability to automate business models within an open framework
Kata Kunci Pencarian:
- Bandar Udara Debre Marqos
- Bulog
- Bluetooth
- Daya
- Paus (mamalia)
- Televisi digital di Indonesia
- Frekuensi ultra tinggi
- Muhammad Amrullah
- Universitas Katolik Widya Mandala Surabaya
- Dun & Bradstreet
- DBm
- DBM
- PTD-DBM
- DBM (computing)
- Database
- Decibel
- Department of Budget and Management
- Difference bound matrix
- Oracle Database
- Transmission level point
