常規(guī)調(diào)幅(am)和抑制載波雙邊帶(dsb)調(diào)制與解調(diào)實(shí)驗(yàn)

#r長(zhǎng)曲前帝調(diào)l：＜逅陂方創(chuàng)AM解詢倍弓謖形21.5丄胡-FIR斛調(diào)IDSB-FIR解調(diào)IDSB-IFffi調(diào)10.52005?012015202?9319051991995數(shù)霜蚩埶選博區(qū)x10'載液信號(hào)振幅AO[io已調(diào)信號(hào)振幅A2[3信號(hào)調(diào)制度m0.15謂制壟E振帽如三csb=^?k|門載誡信號(hào)城率，|一亍帛注；實(shí)驗(yàn).卸L蘊(yùn)軌為A3-10;盧1-弱A2-3ik-O.L'-3DOCsIi-C.'C退出如圖7.5GUI演示DSB解調(diào)濾波后的波形八、結(jié)果分析本設(shè)計(jì)圓滿的完成了對(duì)AM—DSB信號(hào)實(shí)現(xiàn)調(diào)制與解調(diào)，與課題的要求十分相符；也較好的完成了對(duì)AM—DSB信號(hào)的時(shí)域分析，通過(guò)fft變換，得出了調(diào)制信號(hào)和解調(diào)信號(hào)的頻譜圖；在濾波這一部分，課題主要是從巴特沃斯濾波器入手來(lái)設(shè)計(jì)低通濾波器等入手，實(shí)現(xiàn)了預(yù)期的濾波效果。在設(shè)計(jì)FIR低通濾波器的時(shí)候，通帶邊界頻率設(shè)定為載波信號(hào)頻率Fp=f，阻帶截止頻率Fs=f+20,采樣頻率Ft=8f；在設(shè)計(jì)IIR低通濾波器的時(shí)候，通帶邊界頻率設(shè)定為Fp=f-50,阻帶截止頻率Fs=f，采樣頻率Ft=10f。這樣設(shè)定后，在改變載波信號(hào)頻率的時(shí)候就有可能使濾波器無(wú)法進(jìn)行正常的濾波，從而得不到正確的結(jié)果。載波頻率f可以選的高一些，在設(shè)計(jì)的時(shí)候時(shí)間采樣t的間隔就要大一些。完成了界面的設(shè)計(jì)，但也存在許多的不足，顯示已定濾波前后的波形圖，界面沒(méi)有用到其它的一些控件，如列表框、下拉菜單等等，GUI的界面設(shè)計(jì)功能沒(méi)能得到充分的發(fā)揮。

九、結(jié)束語(yǔ)調(diào)制與解調(diào)技術(shù)是通信電子線路課程中一個(gè)重要的環(huán)節(jié)，也是實(shí)現(xiàn)通信必不可少的一門技術(shù)，也是通信專業(yè)學(xué)生必須掌握的一門技術(shù)。課題在這里是把要處理的信號(hào)當(dāng)做一種特殊的信號(hào)，即一種“復(fù)雜向量”來(lái)看待。也就是說(shuō)，課題更多的還是體現(xiàn)了數(shù)字信號(hào)處理技術(shù)。從課題的中心來(lái)看，課題“基于Matlab的AM-DSB調(diào)制系統(tǒng)仿真”是希望將AM-DSB調(diào)制與解調(diào)技術(shù)應(yīng)用于某一實(shí)際領(lǐng)域，這里就是指對(duì)信號(hào)進(jìn)行調(diào)制。作為存儲(chǔ)于計(jì)算機(jī)中的調(diào)制信號(hào)，其本身就是離散化了的向量，我們只需將這些離散的量提取出來(lái)，就可以對(duì)其進(jìn)行處理了。這一過(guò)程的實(shí)現(xiàn)，用到了處理數(shù)字信號(hào)的強(qiáng)有力工具M(jìn)ATLAB。通過(guò)MATLAB里幾個(gè)命令函數(shù)的調(diào)用，很輕易的在調(diào)制信號(hào)與載波信號(hào)的理論之間搭了一座橋。課題的特色在于它將調(diào)制信號(hào)看作一個(gè)向量，于是就把調(diào)制信號(hào)數(shù)字化了。那么，就可以完全利用數(shù)字信號(hào)處理和通信電子線路的知識(shí)來(lái)解決AM—DSB調(diào)制問(wèn)題。我們可以像給一般信號(hào)做頻譜分析一樣，來(lái)對(duì)調(diào)制信號(hào)做頻譜分析，也可以較容易的用數(shù)字濾波器來(lái)對(duì)解調(diào)信號(hào)進(jìn)行濾波處理。通過(guò)比較AM—DSB調(diào)制與解調(diào)前后，調(diào)制信號(hào)的頻譜和時(shí)域，能明顯的感覺(jué)到AM—DSB調(diào)制后AM—DSB解調(diào)與原始的調(diào)制信號(hào)有明顯的不同,設(shè)計(jì)部同的濾波器得到的結(jié)果頁(yè)是不同的，通過(guò)仿真可以看到FIR低通濾波器要比IIR低通濾波器要濾的好。由此可見(jiàn)，調(diào)制信號(hào)主要分布在低頻段，而載波信號(hào)主要分布在高頻段。最后，還利用了MATLAB的另一強(qiáng)大功能一一GUI界面設(shè)計(jì)。設(shè)計(jì)出了一個(gè)簡(jiǎn)易的用戶應(yīng)用界面，可以讓人實(shí)現(xiàn)界面操作，更加方便的進(jìn)行AM—DSB的頻譜分析與調(diào)制和解調(diào)的濾波處理。附錄：GUI設(shè)計(jì)程序如下functionvarargout=AM_DSB_Experiment_Platform_base_on_Matlab(varargin)gui_Singleton=1;gui_State=struct('gui_Name',mfilename,...'gui_Singleton',gui_Singleton,...'gui_OpeningFcn',@AM_DSB_Experiment_Platform_base_on_Matlab_OpeningFcn,...'gui_OutputFcn',@AM_DSB_Experiment_Platform_base_on_Matlab_OutputFcn,...'gui_LayoutFcn',[],...'gui_Callback',[]);ifnargin&&ischar(varargin{l})gui_State.gui_Callback=str2func(varargin{1});endifnargout[varargout{1:nargout}]=gui_mainfcn(gui_State,varargin{:});elsegui_mainfcn(gui_State,varargin{:});endfunctionAM_DSB_Experiment_Platform_base_on_Matlab_OpeningFcn(hObject,eventdata,handles,varargin)handles.output=hObject;guidata(hObject,handles);functionvarargout=AM_DSB_Experiment_Platform_base_on_Matlab_OutputFcn(hObject,eventdata,handles)varargout{1}=handles.output;functionpushbutton1_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalA0;%載波信號(hào)振幅globalw0;globalt%抽樣時(shí)間

globalUc;t=-1:0.00001:1;Uc=AO.*cos(wO*t);plot(t,Uc);title('載波信號(hào)')；axis([0,0.01,-15,15]);T1=fft(Uc);%載波信號(hào)axes(handles.axes2)cla;plot(abs(Tl));title('載波信號(hào)頻譜')；axis([5800,6200,0,1000000]);functionpushbutton2_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalA1;globalw0;globalt;globalmes;mes=A1*cos(0.001*w0*t);plot(t,mes);title('調(diào)制信號(hào)波形')；T2=fft(mes);%調(diào)制信號(hào)振幅%抽樣時(shí)間%調(diào)制信號(hào)axes(handles.axes2)cla;plot(abs(T2));title('調(diào)制信號(hào)頻譜')；axis([198000,202000,0,1000000]);functionpushbutton3_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalA2;globalw0;globalt;globalm;globalmes%已調(diào)信號(hào)振幅%抽樣時(shí)間%信號(hào)調(diào)制度globalUam;Uam=A2*(1+m*mes).*cos((wO).*t);plot(t,Uam);title('AM已調(diào)信號(hào)波形')；T3=fft(Uam);%AM已調(diào)信號(hào)axes(handles.axes2)cla;plot(abs(T3));title('AM已調(diào)信號(hào)頻譜')；axis([5950,6050,0,500000]);%Executesonbuttonpressinpushbutton4.functionpushbutton4_Callback(hObject,eventdata,handles)axes(handles.axesl)cla;globalt;%抽樣時(shí)間globalm;%信號(hào)調(diào)制度globalk;%DSB信號(hào)振幅globalUdsb;globalUc;globalmes;Udsb=k*mes.*Uc;%DSB已調(diào)信號(hào)plot(t,Udsb);gridon;title('DSB已調(diào)信號(hào)波形');axes(handles.axes2)cla;Y4=fft(Udsb);%對(duì)DSB已調(diào)信號(hào)進(jìn)行傅里葉變換plot(abs(Y4)),grid;title('DSB已調(diào)信號(hào)頻譜');axis([193960,194040,0,1300000]);%Executesonbuttonpressinpushbutton5.functionpushbutton5_Callback(hObject,eventdata,handles)axes(handles.axesl)cla;globalb21;Ft=2000;%采樣頻率fpts=[100120];%通帶邊界頻率fp=fHz，阻帶截止頻率fs=f+20Hzmag=[10];dev=[0.010.05];%通帶波動(dòng)1%,阻帶波動(dòng)5%[n21,wn21,beta,ftype]=kaiserord(fpts,mag,dev,Ft);%kaiserord估計(jì)采用凱塞窗設(shè)計(jì)的FIR濾波器的參數(shù)b21=fir1(n21,wn21,Kaiser(n21+1,beta));%由fir1設(shè)計(jì)濾波器[h,w]=freqz(b21,1);%得到頻率響應(yīng)plot(w/pi,abs(h));gridon

title（'FIR低通濾波器'）;%Executesonbuttonpressinpushbutton6.functionpushbutton6_Callback(hObject,eventdata,handles)axes(handles.axes2)cla;globalnumll;globalden11;Ft=1500;Fp=30;Fs=50;wp=2*pi*Fp/Ft;ws=2*pi*Fs/Ft;fp=2*Ft*tan(wp/2);fs=2*Fs*tan(wp/2);[n11,wn11]=buttord(wp,ws,1,50,'s');%求低通濾波器的階數(shù)和截止頻率[b11,a11]=butter(n11,wn11,'s');%求S域的頻率響應(yīng)的參數(shù)[num11,den11]=bilinear(b11,a11,0.5);%雙線性變換實(shí)現(xiàn)S域到Z域的變換[h,w]=freqz(num11,den11);%根據(jù)參數(shù)求出頻率響應(yīng)plot(w*800*0.5/pi,abs(h));title('IIR低通濾波器')；legend('用巴特沃斯butter設(shè)計(jì)')；%Executesonbuttonpressinpushbutton7.functionpushbutton7_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalw0;globalt;%抽樣時(shí)間globalUam;Dam=Uam.*cos(wO*t);%對(duì)AM已調(diào)信號(hào)進(jìn)行解調(diào)plot(t,Dam);gridon;title('濾波前AM解調(diào)波形')；axes(handles.axes2)cla;%plot(abs(Y5)),grid;title('濾波前AM解調(diào)頻譜')；axis([187960,188040,0,200000]);%Executesonbuttonpressinpushbutton8.functionpushbutton8_Callback(hObject,eventdata,handles)axes(handles.axesl)cla;globalwO;globalt;globalUdsb;Ddsb=Udsb.*cos(w0*t);%對(duì)DSB已調(diào)信號(hào)進(jìn)行解調(diào)plot(t,Ddsb);gridon;title('濾波前DSB解調(diào)波形')；axes(handles.axes2)cla;Y6=fft(Ddsb);%對(duì)DSB已調(diào)信號(hào)進(jìn)行傅里葉變換plot(abs(Y6)),grid;title('濾波前DSB解調(diào)頻譜');axis([187960,188040,0,1300000]);%Executesonbuttonpressinpushbutton9.functionpushbutton9_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalw0;globalt;globalb21;globalUam;Dam=Uam.*cos(w0*t);%對(duì)AM調(diào)制信號(hào)進(jìn)行解調(diào)z21=fftfilt(b21,Dam);%FIR低通濾波plot(t,z21,'r');title('濾波后的AM解調(diào)信號(hào)波形')；T5=fft(z21);%求AM信號(hào)的頻譜axes(handles.axes2)cla;plot(abs(T5),'r');title('濾波后的AM解調(diào)信號(hào)頻譜')；axis([198000,202000,0,200000]);%Executesonbuttonpressinpushbutton10.functionpushbutton10_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalw0;globalt;globalnumll;globaldenll;globalUam;Dam=Uam.*cos(wO*t);%對(duì)AM已調(diào)信號(hào)進(jìn)行解調(diào)z11=filter(num11,den11,Dam);%IIR濾波器濾波plot(t,z11,'r');title('濾波后的AM解調(diào)信號(hào)波形')；T6=fft(z11);%求AM信號(hào)的頻譜axes(handles.axes2)cla;plot(abs(T6),'r');title('濾波后的AM解調(diào)信號(hào)頻譜')；axis([198000,202000,0,200000]);%Executesonbuttonpressinpushbutton11.functionpushbutton11_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalw0;globalt;globalUdsb;globalb21;Ddsb=Udsb.*cos(w0*t);%對(duì)DSB調(diào)制信號(hào)進(jìn)行解調(diào)z21=fftfilt(b21,Ddsb);%FIR低通濾波plot(t,z21,'r');title('濾波后的DSB解調(diào)信號(hào)波形')；T7=fft(z21);%求DSB信號(hào)的頻譜axes(handles.axes2)cla;plot(abs(T7),'r');title('濾波后的DSB解調(diào)信號(hào)頻譜')；axis([198000,202000,0,200000]);%Executesonbuttonpressinpushbutton12.functionpushbutton12_Callback(hObject,eventdata,handles)axes(handles.axes1)cla;globalw0;globalt;globalUdsb;globalnumll;globaldenll;Ddsb=Udsb.*cos(wO*t);%對(duì)DSB調(diào)制信號(hào)進(jìn)行解調(diào)zll=filter(numll,denll,Ddsb);%IIR濾波器濾波plot(t,zll,'r');title('濾波后的DSB解調(diào)信號(hào)波形')；T8=fft(zll);%求DSB信號(hào)的頻譜axes(handles.axes2)cla;plot(abs(T8),'r');title('濾波后的DSB解調(diào)信號(hào)頻譜')；axis([l98000,202000,0,200000]);functionpushbuttonl3_Callback(hObject,eventdata,handles)close(gcbf);quit;functioneditl_Callback(hObject,eventdata,handles)globalAO;fl=str2double(get(handles.editl,'string'));A0=fl;functioneditl_CreateFcn(hObject,eventdata,handles)ifispc&&isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunctionedit2_Callback(hObject,eventdata,handles)globalAl;f2=str2double(get(handles.edit2,'string'));Al=f2;functionedit2_CreateFcn(hObject,eventdata,handles)ifispc&&isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunctionedit3_Callback(hObject,eventdata,handles)globalA2;f3=str2double(get(handles.edit3,'string'));A2=f3;functionedit3_CreateFcn(hObject,eventdata,handles)ifispc&&isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunctionedit4_Callback(hObject,eventdata,handles