shiyan3.m

基于matlab实现的双线性变换法设计滤波器

function varargout = shiyan3(varargin)
% SHIYAN3 Application M-file for shiyan3.fig
%    FIG = SHIYAN3 launch shiyan3 GUI.
%    SHIYAN3('callback_name', ...) invoke the named callback.

% Last Modified by GUIDE v2.0 06-May-2003 08:27:14

if nargin == 0  % LAUNCH GUI

	fig = openfig(mfilename,'reuse');

	% Generate a structure of handles to pass to callbacks, and store it. 
	handles = guihandles(fig);
	guidata(fig, handles);

	if nargout > 0
		varargout{1} = fig;
	end

elseif ischar(varargin{1}) % INVOKE NAMED SUBFUNCTION OR CALLBACK

	try
		if (nargout)
			[varargout{1:nargout}] = feval(varargin{:}); % FEVAL switchyard
		else
			feval(varargin{:}); % FEVAL switchyard
		end
	catch
		disp(lasterr);
	end

end
% --------------------------------------------------------------------
function varargout = T_pushbutton1_Callback(h, eventdata, handles, varargin)
% global x;
x=[-4,-2,0,-4,-6,-4,-2,-4,-6,-6,-4,-4,-6,-6,-2,6,12,8,0,-16,-38,-60,-84,-90,-66,-32,...
      -4,-2,-4,8,12,12,10,6,6,6,4,0,0,0,0,0,-2,-4,0,0,0,-2,-2,0,0,-2,-2,-2,-2,0,0];
k=1;
subplot(2,2,2);
n=0:56;
stem(n,x,'.');
% axis([0 56 -100 50]);
hold on
n=0:60;
m=zeros(61);
plot(n,m);
xlabel('n');
ylabel('x(n)');
title('心电图信号');
hold off
% B=[0.09036 2*0.09036 0.09036];
B=eval(get(handles.T_edit1,'string'));
% C=B;
% keyboard;
% A=[1.2686 -0.7051];    %滤波器分母系数向量的第一个数默认为一故省掉不写 A=[1 1.2686 -0.7051]
A=eval(get(handles.T_edit2,'string'));
C1=A;
A1=eval(get(handles.T_edit3,'string'));
% A1=[1.0106 -0.3583];
%A1=[1 1.0106 -0.3583]
A2=eval(get(handles.T_edit4,'string'));
% A2=[0.9044 -0.2155];                                                  %A2=[1 0.9044 -0.2155]
while(k<=3)
   y=filter(B,A,x);    %A为滤波器的分母系数向量,B为滤波器的分母系数向量
   x=y;                %三次递归代算
   if k==2
      A=A1;
   end
   if k==3
      A=A2;
   end
   k=k+1;
end
subplot(2,2,3);
n=0:56;
stem(n,y,'.');
% axis([0 56 -15 5]);
hold on
n=0:60;
m=zeros(61);
plot(n,m);
xlabel('n');
ylabel('y(n)');
title('经过滤波后的心电图信号');
hold off
% A=[0.09036,0.1872,0.09036];      %用B来代替
A=B;
% B1=[1,-1.2686,0.7051];           %用C1来变换获得
C1=-C1;
B1=str2num(['1 ',num2str(C1)]);
% B2=[1,-1.0106,0.3583];              %用A1来变换获得
A1=-A1;
A1=['1 ',num2str(A1)];
B2=str2num(A1);
% B3=[1,-0.9044,0.2155];              %用A2来变换获得
A2=-A2;
B3=str2num(['1 ',num2str(A2)]);
[H1,w]=freqz(A,B1,128);
[H2,w]=freqz(A,B2,128);
[H3,w]=freqz(A,B3,128);
H4=H1.*(H2);
H=H4.*(H3);
mag=abs(H);
db=20*log10((mag+eps)/max(mag));
subplot(2,2,4);
plot(w/pi,db);
axis([0,0.5,-50,10]);
xlabel('w');
ylabel('db');
title('滤波器的幅频响应特性');