Movatterモバイル変換

[0]ホーム
URL:

Jump to content
WikipediaThe Free Encyclopedia
Search

dBc

From Wikipedia, the free encyclopedia
Unit used in signals

dBc (decibels relative to thecarrier) is the power ratio of a signal to acarrier signal, expressed indecibels. For example,phase noise is expressed in dBc/Hz at a givenfrequency 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 adigital-to-analog converter or afrequency mixer.

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 thedecibel (dB) is permitted for use alongsideSI units, the dBc is not.[1]

Example

[edit]

If a carrier (reference signal) has a power ofC=0.1mW{\textstyle \mathrm {C} =0{.}1\,\mathrm {mW} }, and noise signal has power ofS=10μW{\textstyle \mathrm {S} =10\,\mathrm {\mu W} }.

Power of reference signal expressed in decibel is :

PC=10log10⁡(0.1mW1mW)=−10dBm{\displaystyle P_{\mathrm {C} }=10\log _{10}\left({\frac {0{.}1\,\mathrm {mW} }{1\,\mathrm {mW} }}\right)=-10\,\mathrm {dBm} }

Power of noise expressed in decibel is :

PS=10log10⁡(10μW1mW)=−20dBm{\displaystyle P_{\mathrm {S} }=10\log _{10}\left({\frac {10\,\mathrm {\mu W} }{1\,\mathrm {mW} }}\right)=-20\,\mathrm {dBm} }

The calculation of dBc difference between noise signal and reference signal is then as follows:

PS−PC=−20dBm−(−10dBm)=−10dBc{\displaystyle P_{\mathrm {S} }-P_{\mathrm {C} }=-20\,\mathrm {dBm} -(-10\,\mathrm {dBm} )=-10\,\mathrm {dBc} }

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:

PS−PC=10log10⁡(SC)=10log10⁡(10μW0.1mW)=−10dBc{\displaystyle P_{\mathrm {S} }-P_{\mathrm {C} }=10\log _{10}\left({\frac {\mathrm {S} }{\mathrm {C} }}\right)=10\log _{10}\left({\frac {10\,\mathrm {\mu W} }{0{.}1\,\mathrm {mW} }}\right)=-10\,\mathrm {dBc} }.

References

[edit]
  1. ^Taylor 1995, Guide for the Use of the International System of Units (SI), NIST Special Publication SP811

External links

[edit]


Stub icon

This technology-related article is astub. You can help Wikipedia byadding missing information.

Retrieved from "https://en.wikipedia.org/w/index.php?title=DBc&oldid=1204391204"
Categories:
Hidden categories:
[8]ページ先頭
©2009-2026 Movatter.jp