MATLAB: Plomb command and how I convert units!!

plomb convert db dbw/hz

Hallo after applying the plomb command to a non-uniform sample and I got the PSD that I wanted! The thing I want to know is want are the units of the Power at the y axis? And how can I convert them to dB or at dBW/Hz?? Thanks!!

Best Answer

The documentation for the plomb function allows you to specify the output as 'psd', 'power' or 'normalized' (see the section on the spectrumtype (link) argument). Since the 'psd' option is the default, that will give you the result in units of db/Hz. If your original data are in Volts (amplitude) the output will be in terms of Watts (power). Choose the output option you want.

At least that is how I always understood power spectral density calculations.

Related Solutions

MATLAB: The results of ‘plomb’ are different than the expectations

Please read our documentation for this function:

https://mathworks.com/help/signal/ref/plomb.html

Please consider to set the spectrum type correctly:

[___] = plomb(_,<https://de.mathworks.com/help/signal/ref/plomb.html#buio4ln-1-spectrumtype spectrumtype>) specifies the normalization of the periodogram.

Set spectrumtype to 'psd', or leave it unspecified, to obtain pxx as a power spectral density.
Set spectrumtype to 'power' to get the power spectrum of the input signal.
Set spectrumtype to 'normalized' to get the standard Lomb-Scargle periodogram, which is scaled by two times the variance of x.

MATLAB: How to convert data from dBW units to dBm in MATLAB 7.5 (R2007b)

Assuming that Pxx is measured in Watts, the formula for dBW is

       dBW = 10*log10(Pxx/(1 Watt))
          = 10*log10(Pxx)             for Pxx in Watts

The formula for dBm is

      dBm = 10*log10((1000 mW/W)*Pxx /(1 milliWatt))
          = 10*log10(1000*Pxx)
          = 10*log10(Pxx) + 10*log10(1000)
          = 10*log10(Pxx) + 10*(3)
          = 10*log10(Pxx) + 30
          = dBW + 30

Best Answer

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MATLAB: The results of ‘plomb’ are different than the expectations

MATLAB: How to convert data from dBW units to dBm in MATLAB 7.5 (R2007b)

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