包络检波.ZIP_matlab 检波_matlab包络检波_包络_包络检波_包络检波matlab

%++++++++++++++++++++以下程序实现包络检波++++++++++++++% echo on t0=0.15; %signal duration ts=0.001; %sampling interval fc=250; %carrier frequency a=0.85; %modulated index fs=1/ts; %samples frequency t=[0:ts:t0];%time vector df=0.25; %required frequency resolution %message signal m=[ones(1,t0/(3*ts)),-2*ones(1,t0/(3*ts)),zeros(1,t0/(3*ts)+1)]; c=cos(2*pi*fc.*t);%carrier signal m_n=m/max(abs(m));%normalized message signal [M,m,df1]=fftseq(m,ts,df);%fourier transform f=(0:df1:df1*(length(m)-1))-fs/2;%frequency vector u=(1+a*m_n).*c;% modulated signal [U,u,df1]=fftseq(u,ts,df);%fourier transform env=env_phas(u);%find the envelope dem1=2*(env-1)/a;%remove DC and scale signal_power=spower(u(1:length(t)));%power in modulated signal noise_power=signal_power/100;%noise power noise_std=sqrt(noise_power);%noise standard deviation noise=noise_std*randn(1,length(u));%generate noise r=u+noise; %add noise to the modulated signal [R.r.df1]=fftseq(r,ts,df); %fourier transform env_r=env_phas(r); %envelope, when noise is present dem2=2*(env_r-1); %demodulate in the presence of noise pause; %press any key to see a plot of message subplot(2,1,1); plot(t,m(1:length(t))); axis([0 0.15 -2.1 2.1]); xlabel('time') title('the message signal '); pause; %press any key to see a plot of the modulated signal subplot(2,1,2); plot(t,u(1:length(t))); axis([0 0.15 -2.1 2.1]); xlabel('time') title('the modulated signal '); pause; %press any key to see the envelope of the message modulated signal clf; subplot(2,1,1); plot(t,u(1:length(t))); axis([0 0.15 -2.1 2.1]); xlabel('time') title('the modulated signal '); subplot(2,1,2); plot(t,env(1:length(t))); xlabel('time') title('envelope of the modulated signal '); pause; %press any key to compare the message and the demodulated signal clf; subplot(2,1,1); plot(t,m(1:length(t))); axis([0 0.15 -2.1 2.1]); xlabel('time') title('the message signal '); subplot(2,1,2); plot(t,dem1(1:length(t))); xlabel('time') title('the modulated signal '); pause; %press any key to compare in the presence of the noise subplot(2,1,1); plot(t,m(1:length(t))); axis([0 0.15 -2.1 2.1]); xlabel('time') title('the message signal '); subplot(2,1,2); plot(t,dem2(1:length(t))); xlabel('time') title('the modulated signal in the presence of noise ');