EC 6120 and EC 5102 DSP MATLAB PROGRAMS DAY 5

PROGRAMS FOR FILTERING LONG DATA SEQUENCES

%Program for MATLAB 7 users where circular convolution function is not in built
%if present the present program (a function) to b saved as ECEE.m can be replaced by 'cconv' command

function [c]=ECEE(a,b,N)

% a=[1 2 3 4];%input

% b=[1 2 -1 -2];%input

% N=6;%number of points

A=fft(a,N);

B=fft(b,N);

C=A.*B;

c=ifft(C,N);

OVERLAP SAVE METHOD

%Filtering long data sequence using OVERLAP SAVE METHOD

clc

clear all

close all

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

x=[1 2 -1 2 3 -2 -3 -1 1 1 2 -1];%input

h=[1 2 1 1];%system

N=4;%length of each block

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

yy=conv(x,h);

subplot 311, stem(yy)

title('Using LONG linear filtering')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if (N

    error('N must be >=length(h)')

end

Nx=length(x);

M=length(h);

M1=M-1;

L=N-M1;

x=[zeros(1,M-1), x, zeros(1,N-1)];

h=[h zeros(1,N-M)];

K=floor((Nx+M1-1)/L);%no of blocks

y=zeros(K+1,N);

%dividing sequence in k blocks

for k=0:K

    xk=x(k*L+1:k*L+N);

    Y(k+1,:)=ECEE(xk,h,N);

end

Y=Y(:,M:N)';

y=(Y(:))';

subplot 312, stem(y)

title('Using Overlap SAVE method')

d=yy-y(1:length(yy));

subplot 313, stem(d)

title('Difference')

OVERLAP ADD METHOD

%Filtering long data sequence using OVERLAP ADD METHOD

clc

clear all

close all

x=[1 2 -1 2 3 -2 -3 -1 1 1 2 -1];%input

h=[1 2 1 1];%system

L=4;%length of each block

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

yy=conv(x,h);

subplot 311, stem(yy)

title('Using LONG linear filtering')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Nx=length(x);

M=length(h);

M1=M-1;

R=rem(Nx,L);

N=L+M1;

x=[x zeros(1,L-R)];

h=[h zeros(1,N-M)];

K=floor(Nx/L); % number of blocks

y=zeros(K+1,N);

z=zeros(1,M1);

%dividing to K blocks

for k=0:K

    xp=x(L*k+1:L*k+L);

    xk=[xp z];

    y(k+1,:)=ECEE(xk,h,N);

end

yp=y';

[x,y]=size(yp);

for i=L+1:x;

    for j=1:y-1

        temp1=i-L;

        temp2=j+1;

        temp3=yp(temp1,temp2)+yp(i,j);

        yp(temp1,temp2)=temp3;

    end

end

z=1;

for j=1:y

    for i=1:x

        if ((i<=L & j<=y-1)|(j==y))

            ypnew(z)=yp(i,j);

            z=z+1;

        end

    end

end

y=ypnew;

subplot 312, stem(y)

title('Using Overlap Add method')

d=yy-y(1:length(yy));

subplot 313, stem(d)

title('Difference')