%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

%%            Output Info about this m-file

fprintf('\n***********************************************************\n');

fprintf('        <DSP using MATLAB> Problem 6.13 \n\n');

banner();

%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

b1 = [0.5   2.0  1.5]; a1 = [1.0   1.0  0.9];

b2 = [1.0   3.0];      a2 = [1.0  -1.0  0.8];

b3 = [1.0   2.0  1.0]; a3 = [1.0  0.5  0.5  -0.4];

b4 = [3.0  -0.5  2.0]; a4 = [1.0  0.4  0.4];   

a12 = conv(a1, a2); b12 = conv(b1, b2);

a34 = conv(a3, a4); b34 = conv(b3, b4);

format short;

fprintf('\nDIRECT-form:     \n');

a = conv(a12, a34)

b = conv(b12, a34)+ conv(b34, a12)

fprintf('\nConvert DIRECT-form to PARALLEL-form :     \n');

[C, Bp, Ap] = dir2par(b, a)

if size(C)==0

  C = 0;

end

fprintf('\nConvert DIRECT-form to CASCADE-form :     \n');

[b0, Bc, Ac] = dir2cas(b, a) 

fprintf('\nConvert TF-form to SOS-form :     \n');

[sos, g] = tf2sos(b, a)

fprintf('\nConvert DIRECT-form to LATTICE-LADDER-form :     \n');

[Klr, Clr] = dir2ladr(b, a) 

fprintf('\nConvert DIRECT-form to MATLAB LATTICE-LADDER-form :     \n');

[K, V] = tf2latc(b, a)

% -----------------------------------------

%     START check

% -----------------------------------------

n = [0:7];

delta = impseq(0, 0, 7)

%format long

format  short

hcas = casfiltr(b0, Bc, Ac, delta)

hpar = parfiltr(C, Bp, Ap, delta)

hladr = ladrfilt(Klr, Clr, delta)

hdir = filter(b, a, delta)

% -------------------------------------------

%       END check

% -------------------------------------------

fprintf('\nConvert CASCADE-form to DIRECT-form:     \n');

[b_c2d, a_c2d] = cas2dir(b0, Bc, Ac) 

fprintf('\nConvert SOS-form to TF-form :     \n');

[b_s2t, a_s2t] = sos2tf(sos, g)