A low pass digital filter (IIR) is designed based on given specifications. Butterworth analog filter H(s) is designed first, then it is converted to digital filter (Hz).
An analytical procedure is illustrated below and simplified to allow one to more easily program the algorithm. 4 numerical examples are used to illustrate the procedure.
Mathematica GUI program is written also to implement the above. It can be downloaded from here: HTML
A simple Matlab script is also written (no GUI) to implement this design. Here is the Matlab script (written on Matlab 2007a). Note this script does not handle the coversion from H(s) to H(z) well yet, need to work more on this... ofcourse, one can just use Matlab butter() function nma_filter.m
The output of the Matlab script is here matlab_output.txt