1/问题模型：已知一信号通过一黑匣子后输出另一信号，待求经过该黑匣子的一输入信号对应的输出信号；
2/分析：问题重点在于求解该模型传递函数，根据传递的定义，我们可以分别求出输入与输出信号的FFT变换，然后相除，在matlab中，直接按此法求解还是教复杂的。
具体求解实例过程如下图示：
来源：盛谦等，传递函数在地下工程地震响应中的应用
3/具体：先又输入与输出数据经系统辨识得出传递函数，然后将输入信号FFT变换成傅里叶谱，与传涵的实部、虚部相乘，得到频域估算结果，经IFFT变换得到时域估算结果。
在matlab中通过tfe可以对传函进行估算，绘出传递函数的幅频图与相频图。
4/下面是一个简单的实例：
下图分别为任意取定的一输入与输出信号
经系统辨识后绘出的幅频与相频如下：
找不到关键句了，把m文件粘上来，里面有些GUI的控制句，删掉就可以了
function varargout = CDHS(varargin)
% CDHS MATLAB code for CDHS.fig
% CDHS, by itself, creates a new CDHS or raises the existing
% singleton*.
%
% H = CDHS returns the handle to a new CDHS or the handle to
% the existing singleton*.
%
% CDHS('CALLBACK',hObject,eventData,handles,...) calls the local
% function named CALLBACK in CDHS.M with the given input arguments.
%
% CDHS('Property','Value',...) creates a new CDHS or raises the
% existing singleton*. Starting from the left, property value pairs are
% applied to the GUI before CDHS_OpeningFcn gets called. An
% unrecognized property name or invalid value makes property application
% stop. All inputs are passed to CDHS_OpeningFcn via varargin.
%
% *See GUI Options on GUIDE's Tools menu. Choose "GUI allows only one
% instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES
% Edit the above text to modify the response to help CDHS
% Last Modified by GUIDE v2.5 03-Dec-2013 10:11:36
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @CDHS_OpeningFcn, ...
'gui_OutputFcn', @CDHS_OutputFcn, ...
'gui_LayoutFcn', [] , ...
'gui_Callback', []);
if nargin && ischar(varargin{1})
gui_State.gui_Callback = str2func(varargin{1});
end
if nargout
[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT
% --- Executes just before CDHS is made visible.
function CDHS_OpeningFcn(hObject, eventdata, handles, varargin)
global s1 s2 hest1 f fs k4 k5 a real1 imag1 angle1;
% This function has no output args, see OutputFcn.
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% varargin command line arguments to CDHS (see VARARGIN)
% Choose default command line output for CDHS
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes CDHS wait for user response (see UIRESUME)
% uiwait(handles.figure1);
% --- Outputs from this function are returned to the command line.
function varargout = CDHS_OutputFcn(hObject, eventdata, handles)
% varargout cell array for returning output args (see VARARGOUT);
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Get default command line output from handles structure
varargout{1} = handles.output;
% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
[filename,pathname]=uigetfile('*.xls','input the signal');
global s1 s2 hest1 f fs k4 k5 a real1 imag1 angle1;
file=[filename,pathname];
singal=xlsread(filename);
s1=singal(:,2);
k1=singal(2,1);
k2=singal(3,1);
k3=k2-k1;
fs=1/k3;
k4=length(s1);
k5=2*(k4-1);
% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
global s1 s2 hest1 f fs k4 k5 a real1 imag1 angle1;
[filename2,pathname2]=uigetfile('*.xls','input the signal');
file2=[filename2,pathname2];
sigal2=xlsread(filename2);
s2=sigal2(:,2);
% --- Executes on button press in pushbutton3.
function pushbutton3_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton3 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
global s1 s2 hest1 f fs k4 k5 a real1 imag1 angle1;
[hest1,f]=tfe(s1,s2,k5,fs,k4,0,'mean');
real1=real(hest1);
imag1=imag(hest1);
% --- Executes on button press in pushbutton4.
function pushbutton4_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton4 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
global s1 s2 hest1 f fs k4 k5 a real1 imag1 angle1;
a=abs(hest1);%求传涵幅值
plot(f,a);xlabel('Frequency');ylabel('H(w)');title('幅频图');%绘制传涵幅频图
% --- Executes on button press in pushbutton5.
function pushbutton5_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton5 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
global s1 s2 hest1 f fs k4 k5 a real1 imag1 angle1;
angle1=angle(hest1);
angle1=angle1/3.14159*180;%求相角
plot(f,angle1);xlabel('Frequency');ylabel('w');title('相频图');%绘制传涵相频图
% --- Executes on button press in pushbutton6.
function pushbutton6_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton6 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
global s1 s2 hest1 f fs k4 k5 a real1 imag1 angle1;
c=ones(s1,6);
ones(:,1)=f;
ones(:,2)=hest1;
ones(:,3)=real1;
ones(:,4)=imag1;
ones(:,5)=a;
ones(:,6)=angle1;
c1=ones';
outsignal=xlswrite('outcdhs.xls',c1);
% --- Executes on button press in pushbutton7.
function pushbutton7_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton7 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
close(handles.figure1)
