algorithm for implementing IIR digital filter chebyshev type I low pass

hello everyone, i am trying to implement the 'decimate' function in C. through matlab documentation, i found the data are filtered through chebyshev type I low pass filter. FDAToolbox gives me the SOS matrix and scale values of the required filter, but i dont understand how to use them. in fact i dont know what they are. please help me with algorithm or theory. any help is appreciated

Answer 1

[Honglei Chen]

The following document may be helpful to you. SOS is just a different way to implement filters, but it provides better numerical stability in practice.

http://users.etech.haw-hamburg.de/users/Schwarz/En/Lecture/IE8/Notes/Chapt_3.pdf

HTH

[morshed haque]

thank you for your response. it was really helpful for me. but i think i have very little idea about digital filters, which does not give me a clear view. may i get a little more help from here? I have specified my question a little more. could you have a look to help me out. thanks again

Answer 2

[morshed haque]

I am specifying my problem a little more. i want to implement a Chebyshev type I filter in C. fdatoolbox gives me

SOSMatrix sos=

[ 1.0000    2.0000    1.0000    1.0000   -1.1469    0.9449;
  1.0000    2.0000    1.0000    1.0000   -1.2597    0.8424;
  1.0000    2.0000    1.0000    1.0000   -1.4695    0.7549;
  1.0000    2.0000    1.0000    1.0000   -1.6396    0.7005 ]

my scale values are:

scale=

[ 0.1995;
  0.1457;
  0.0713;
  0.0152;
  0.8913 ]

should be the eqn of output y(n) if x is my input?