%% L14_SOS
%% ========
%% Script to illustrate second order sections, which can be imported in
%% fdatool.
%%
%% Created  : 31 Aug 2005
%% Modified : 31 Aug 2005
%%
%% Copyright (c) 2005 Salman Durrani .
%% ------------------------------------------------------------

clc
clear all
close all

%% Define filter coefficients [See DSP Guide (pg 336)]
%% Low pass Chebyshev filter (0.5% passband ripple: type I)
%% fc = 0.5
b0 = 2.858110e-01;
b1 = 5.716221e-01;
b2 = 2.858110e-01;
a1 = 5.423258e-02;
a2 = -1.974768e-01;

%% H(z)
num=[b0 b1 b2];
den=[1 -a1 -a2];

%% Analyse filter
fvtool(num,den)
% axis([0 1 -40 0])

%% Create two second order sections 
SOS = [b0 b1 b2 1 -a1 -a2
       b0 b1 b2 1 -a1 -a2];
    
%% Import into fdatool using "Import Filter From Workspace"
fdatool