Why does the DB function not return the proper power ratio in Signal Processing Toolbox?

Illustration
jasminemichae - 2021-03-16T09:53:19+00:00
Question: Why does the DB function not return the proper power ratio in Signal Processing Toolbox?

I expect DB to always be power ratio and not amplitude ratio. Hence, dB should equal 10*log10 (value) and not 20*log10(value) for amplitude to power conversion.  

Related Questions

  • How do I uninstall and reinstall MathWorks Service Host?
  • MatLab App Design - how to use default value for Edit Field function?
  • What's the difference between imagesc and imshow?
  • Error evaluating parameter 'Value' in simulink
  • Why do I get a connection error when installing or activating MATLAB or other MathWorks products?

    • Expert Answer

    Profile picture of John Williams John Williams answered . 2025-11-20

    This bug has been fixed in Release 2007a (R2007a). For previous product releases, read below for any possible workarounds:
     
    Generally for engineers of communications and electronics background, "dB" unit represents a ratio, for example, between input and output. On the other hand "dBm" unit represents a magnitude of power. However, in this case "dB" is used as a magnitude of power.
     
    You can use the following syntax of the DB function as a workaround. If X is the value in question, use:
     
     
    db(X,'power')
    To get the 10*log10(X) instead of the 20*log10(X).

     


    Not satisfied with the answer ?? ASK NOW

    Get a Free Consultation or a Sample Assignment Review!

    Upload Assignment Talk to Expert