%% L14_Filter_Structure
%% ======================
%% Script to illustrate and compare filter implementation with
%% Matlab and Simulink.
%%
%% Compare with output from demo Simulink file "fxpdemo_direct_form2", 
%% which shows the direct-form II implementation.
%%
%% Created  : 29 Aug 2005
%% Modified : 29 Aug 2005
%%
%% Copyright (c) 2005 Salman Durrani .
%% ------------------------------------------------------------

clc
clear all
close all

%% Filter Coeffs (See Lecture 14)
num=[1 2.2 1.85 0.5];
den=[1 -0.5 0.84 0.09];

%% Square wave frequency (Hz)
f = 0.005;

%% Time vector
t = [0:1:200];

%% Create a square wave of unit amplitude and frequency f
x = -1.*square(2*pi*f*t);

%% Filtered signal
y=filter(num,den,x);

%% Plot results
figure
plot(t,x,'k')
hold on
plot(t,y,'b')
xlabel('Time (s)');
ylabel('Amplitude')
axis([0 Inf -8 10])
legend('input','output')
grid on