Envelope

Envelope of an oscillating signal - sinusoidal or otherwise

Description

This function begins by deducing the wavelength of the signal's primary Fourier component. It then smooths the signal using a moving-window average -- the window is roughly top hat, of size equal to the primary wavelength. For 2-D data it will perform this function on each column of data, using the primary wavelength of the central column throughout.

The only input is the oscillating field. This method works remarkably well in obtaining the laser field envelope from the particle-in-cell simulations I have tested it on (see screenshot).

A possible extension would be to adapt it for a signal with a time-dependent frequency, by implementing a window of position-dependent size.

• MATLAB release: MATLAB 7.7 (R2008b)

[Brian Katz]

I have tried this on some data, and the results do not seem correct. I am looking at impulse responses (time domain pulse and decay, 240000pt vector). The results does not follow any envelope, and the caluclation time is very long for any appreciable vector sizes (due to the inherent FFT).
It would be benefitial to have a simple example in the help to be sure that the function works correctly.