How can i make a smoothed envelope of my complex (random) signal?

I would like to plot a envelope over my random signal (complex). My matlab does not support the function 'envelope'. Any ideas how I can do this?

Thanks in advanced.

stijn

[Adam]

The envelope is just

abs( myComplexSignal );

and if you want the full enclosing envelope, just the negation of this as well.

[Stijn Hillenius]

Yes I agree this is an envelope. My question was badly formulated. I would like a smoothed envelope, since my signal is not smooth at all. Sorry for not making my self clear..

[Adam]

Smoothing is something of a black art and depends entirely on your data, what you want to get from it, etc, etc.

You could just slap a length 5 mean filter over your envelope to smooth it, but that is very aggressive.

Or you can use a Savitzky-Golay filter

doc sgolay

to do some post smoothing. That requires a lot of parameterisation though which again depends on just how smooth you want it vs how much of your data you want to retain.

[Stijn Hillenius]

Thank you

Answer 1

[Star Strider]

The envelope (link) function uses the absolute value of the hilbert (link) function. Use that instead.

For more information, see Envelope Extraction Using the Analytic Signal (link).