dBc (decibels relative to the
carrier
Carrier may refer to:
Entertainment
* ''Carrier'' (album), a 2013 album by The Dodos
* ''Carrier'' (board game), a South Pacific World War II board game
* ''Carrier'' (TV series), a ten-part documentary miniseries that aired on PBS in April 20 ...
) is the power ratio of a signal to a
carrier
Carrier may refer to:
Entertainment
* ''Carrier'' (album), a 2013 album by The Dodos
* ''Carrier'' (board game), a South Pacific World War II board game
* ''Carrier'' (TV series), a ten-part documentary miniseries that aired on PBS in April 20 ...
signal, expressed in
decibels
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a pow ...
. For example,
phase noise
In signal processing, phase noise is the frequency-domain representation of random fluctuations in the phase of a waveform, corresponding to time-domain deviations from perfect periodicity (jitter). Generally speaking, radio-frequency engin ...
is expressed in dBc/
Hz at a given
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from '' angular frequency''. Frequency is measured in hertz (Hz) which is ...
offset from the carrier. dBc can also be used as a measurement of Spurious-Free Dynamic Range (
SFDR) between the desired signal and unwanted spurious outputs resulting from the use of signal converters such as a
digital-to-analog converter
In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.
There are several DAC archi ...
or a
frequency mixer
In electronics, a mixer, or frequency mixer, is an electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals are applied to a mixer, and it produces new signals at the sum and di ...
.
If the dBc figure is positive, then the relative signal strength is greater than the carrier signal strength. If the dBc figure is negative, then the relative signal strength is less than carrier signal strength.
Although the
decibel (dB) is permitted for use alongside
SI units, the dBc is not.
Taylor 1995, Guide for the Use of the International System of Units (SI), NIST Special Publication SP811
/ref>
Example
If a carrier (reference signal) has a power of , and noise signal has power of .
Power of reference signal expressed in decibel is :
:
Power of noise expressed in decibel is :
:
The calculation of dBc difference between noise signal and reference signal is then as follows:
:
It is also possible to compute the dBc power of noise signal with respect to reference signal directly as logarithm of their ratio as follows:
: .
References
External links
Units of measurement
Radio frequency propagation
Telecommunications engineering
Logarithmic scales of measurement
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