How does LabVIEW calculate filter coefficients?

[efelgemacher]

I am attempting to develop a model for a post - processing routine that uses a cascaded IIR lowpass filter, in order to demonstrate to a customer the performance of our data acqusition system, without divulging our proprietary source code. Does anyone know how LabVIEW calculates filter coefficents?

[chutla]

Greetings efelgemacher!

I'm going to take a guess, but don't quote me on this. Both Matlab and Labview use IIR to synthesize analog filter prototypes....in a way, it's sort of "dumbing down" of an IIR response to get an analog equivalent. If you "drill down" through any of the Analog filter vi's you will see that they ALL use Digital filters just with analog paramaters plugged in.
At any rate, the polynomials have been catalogued for decades now, and I suspect they reside in a library somewhere in Labview..at least in "low resolution" form, rather than being generated from scratch every time. It would take very little reiteration to generate a couple of more decimal places using the IIR engine.

Again, just an educated guess.

Eric