[sdiy] Block based design was: Favourite VCO designs

[Aaron Lanterman]

On Feb 25, 2010, at 10:40 PM, David G. Dixon wrote:

> We don't do frequency domain modeling in process engineering, generally.
> All process control modeling is done in the Laplace domain.  However, I
> would imagine that structural engineers do a fair bit of it, to analyze
> cyclic stresses on structures, etc.  I've done some frequency domain
> modeling personally, to analyze fluid flow and dispersion in packed beds,
> but this is not a standard technique in chemical engineering.  I never even
> heard about the Fourier transform during my undergraduate days.

If you're in the Laplace domain, the Fourier domain is just a substitution away:

if H(s) is the Laplace transform, then

plug in s = jw, where w is a radial frequency, then bam, you get the Fourier transform. ;)

The Laplace transform can be thought of as an extension of the Fourier transform from the imaginary axis to the complex plane.

- Aaron