Envelope of a signal via Convex hull / Edge detection

1. How do you find the envelope of a signal?
2. What is an envelope of a signal?
3. What is envelope function in Matlab?

How do you find the envelope of a signal?

In the EMD algorithm, the upper and lower envelopes of signals are obtained by using two steps: 1) identify all the local extrema; 2) interpolate between extrema by a cubic spline [9]. The interpolative envelope includes the upper and lower envelopes.

What is an envelope of a signal?

In physics and engineering, the envelope of an oscillating signal is a smooth curve outlining its extremes. The envelope thus generalizes the concept of a constant amplitude into an instantaneous amplitude. The figure illustrates a modulated sine wave varying between an upper envelope and a lower envelope.

What is envelope function in Matlab?

[ yupper,ylower ] = envelope( x ) returns the upper and lower envelopes of the input sequence, x , as the magnitude of its analytic signal. The analytic signal of x is found using the discrete Fourier transform as implemented in hilbert .