《DSP using MATLAB》Problem 6.17

        代码：

%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%%            Output Info about this m-file
fprintf('\n***********************************************************\n');
fprintf('        <DSP using MATLAB> Problem 6.17 \n\n');

banner();
%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%format long;
format short;
fprintf('\n FIR filter DIRECT-form:     \n');
k = [0:6];
b = exp(-0.9*abs(k-3))
a = 1.0


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)

% ----------------------------------------------------------
% NOTE: linear-phase can not use LATTICE-form
% ----------------------------------------------------------
fprintf('\nConvert DIRECT-form to All-Zero LATTICE-form :     \n');
[Klc] = dir2latc(b) 


fprintf('\nConvert DIRECT-form to FREQUENCY-SAMPLE-form :     \n');
[Cfs, Bfs, Afs] = dir2fs(b) 


% -----------------------------------------
%     START check
% -----------------------------------------
n = [0:7];
delta = impseq(0, 0, 7)
%format long
format  short
hcas = casfiltr(b0, Bc, Ac, delta)

%hltc = latcfilt(Klc, delta)

%hladr = ladrfilt(Klr, Clr, delta)

hdir = filter(b, a, delta)
% -------------------------------------------
%       END check
% -------------------------------------------

　　运行结果：

        直接结构形式系数

        串联结构形式系数：

        由差分方程和系统函数的关系得知，该系统脉冲响应是第I类线性相位，故没有Lattice形式。