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⛄ 内容介绍
本文针对"信号与系统"这门课程存在物理概念抽象,学生难以理解等情况,利用MATLAB强大的图形处理功能,结合教学中的重难点,设计了基于MATLAB GUI界面的连续信号滤波处理系统.系统主要功能分数据读取和数据处理.数据读取功能主要是读取待分析的连续时间信号,读取后还可以显示该信号的时域波形和频谱图;数据处理功能主要是设计低通,高通,带通三种典型的滤波器对信号进行滤波处理,处理后的时域图和频谱图能在界面上显示出来.这样,滤波器特性,信号通过滤波器滤波前后的时频变化都可以通过这个系统进行分析.总的来说,系统可分为4个大的模块,分别是:信号读取模块,时域分析模块,滤波器设计模块,频域分析模块.每个模块内部可以对信号进行相应的操作.以实际的连续信号为例,给出了低通滤波器,高通滤波器,带通滤波器的设计,在GUI界面上进行了信号滤波仿真,比较了连续信号通过滤波器前后的效果.结果证明,利用MATLAB平台分析和处理信号与系统,不仅能加深理解,而且还能得到满意的效果.
⛄ 部分代码
function varargout = Lowpass(varargin)
% LOWPASS MATLAB code for Lowpass.fig
% LOWPASS, by itself, creates a new LOWPASS or raises the existing
% singleton*.
%
% H = LOWPASS returns the handle to a new LOWPASS or the handle to
% the existing singleton*.
%
% LOWPASS('CALLBACK',hObject,eventData,handles,...) calls the local
% function named CALLBACK in LOWPASS.M with the given input arguments.
%
% LOWPASS('Property','Value',...) creates a new LOWPASS or raises the
% existing singleton*. Starting from the left, property value pairs are
% applied to the GUI before Lowpass_OpeningFcn gets called. An
% unrecognized property name or invalid value makes property application
% stop. All inputs are passed to Lowpass_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 Lowpass
% Last Modified by GUIDE v2.5 24-Jan-2015 09:39:53
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @Lowpass_OpeningFcn, ...
'gui_OutputFcn', @Lowpass_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 Lowpass is made visible.
function Lowpass_OpeningFcn(hObject, eventdata, handles, varargin)
% 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 Lowpass (see VARARGIN)
% Choose default command line output for Lowpass
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes Lowpass wait for user response (see UIRESUME)
% uiwait(handles.figure1);
% --- Outputs from this function are returned to the command line.
function varargout = Lowpass_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)
wp = str2double(get(handles.edit1,'string'));
ws = str2double(get(handles.edit2,'string'));
if wp<ws
%invisibal the subwindow, visibal main window
set(gcf,'visible','off');
main('visible','on');
else
errordlg('错误！低通滤波器通带截止频率应小于阻带截止频率！','错误提示');
end
function edit1_Callback(hObject, eventdata, handles)
% hObject handle to edit1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit1 as text
% str2double(get(hObject,'String')) returns contents of edit1 as a double
% --- Executes during object creation, after setting all properties.
function edit1_CreateFcn(hObject, eventdata, handles)
% hObject handle to edit1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function edit2_Callback(hObject, eventdata, handles)
% hObject handle to edit2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit2 as text
% str2double(get(hObject,'String')) returns contents of edit2 as a double
% --- Executes during object creation, after setting all properties.
function edit2_CreateFcn(hObject, eventdata, handles)
% hObject handle to edit2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function edit3_Callback(hObject, eventdata, handles)
% hObject handle to edit3 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit3 as text
% str2double(get(hObject,'String')) returns contents of edit3 as a double
% --- Executes during object creation, after setting all properties.
function edit3_CreateFcn(hObject, eventdata, handles)
% hObject handle to edit3 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function edit4_Callback(hObject, eventdata, handles)
% hObject handle to edit4 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of edit4 as text
% str2double(get(hObject,'String')) returns contents of edit4 as a double
% --- Executes during object creation, after setting all properties.
function edit4_CreateFcn(hObject, eventdata, handles)
% hObject handle to edit4 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
% --- Executes on selection change in popupmenu1.
function popupmenu1_Callback(hObject, eventdata, handles)
% hObject handle to popupmenu1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: contents = cellstr(get(hObject,'String')) returns popupmenu1 contents as cell array
% contents{get(hObject,'Value')} returns selected item from popupmenu1
% --- Executes during object creation, after setting all properties.
function popupmenu1_CreateFcn(hObject, eventdata, handles)
% hObject handle to popupmenu1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: popupmenu controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
% --- 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 fs; global a; global b;
wp = str2double(get(handles.edit1,'string'));
ws = str2double(get(handles.edit2,'string'));
rp = str2double(get(handles.edit3,'string'));
rs = str2double(get(handles.edit4,'string'));
sel = get(handles.popupmenu1,'value');
if wp<ws
switch sel
case 1 %butterworth
[n,Wn] = buttord(2*wp/fs,2*ws/fs,rp,rs);
[b,a] = butter(n,Wn);
case 2 %chelbshelf I
[n,Wn] = cheb1ord(2*wp/fs,2*ws/fs,rp,rs);
[b,a] = cheby1(n,rp,Wn);
case 3 %chelbshelf II
[n,Wn] = cheb2ord(2*wp/fs,2*ws/fs,rp,rs);
[b,a] = cheby2(n,rs,Wn);
case 4
[n,Wn] = ellipord(2*wp/fs,2*ws/fs,rp,rs);
[b,a] = ellip(n,rp,rs,Wn);
end
[h,f] = freqz(b,a,1024,fs);
mag = abs(h);
phase = angle(h);
axes(handles.axes1),loglog(f,mag)
axes(handles.axes2),semilogx(f,phase)
else
errordlg('错误！低通滤波器通带截止频率应小于阻带截止频率！','错误提示');
end
⛄ 运行结果
⛄ 参考文献
[1] 窦林涛, 程健庆, 李素民. 基于Matlab的雷达信号处理系统仿真[J]. 指挥控制与仿真, 2006, 28(2):5.
[2] Dong Haibing, 董海兵, Luo Xuelian,等. 连续信号滤波处理系统设计和仿真[C]// 湖南省高校电子信息技术教学研究会. 湖南省高校电子信息技术教学研究会, 2013.
[3] 罗大鹏, 叶敦范, 王勇. 基于Matlab的信号处理系统[J]. 现代电子技术, 2004, 27(19):4.
[4] 王宏, 贾新民. 信号处理基础[M]. 机械工业出版社, 2007.
