jclmgwz.asv

这是有关锁相环的一些必用知识.希望能对大家有所帮助哈

%位置检测
clear

k=15E+10;  %调频斜率
fo=10E+6;%载频
T=40E-6;%脉冲宽度
n=4000;%抽样点数
fs=60E+6;%采样频率
ts=1/fs;%采样时间间隔
t=ts:ts:n*ts;

p=zeros(1,n);
p(500+1:500+T*fs)=ones(1,T*fs);
signal=1/sqrt(T)*cos(2*pi*(fo*t+k*t.^2/2)).*p;
signal_spect=abs(fft(signal));

signal_power=sum(signal.^2);
snr=-7;
noise_power=signal_power*10^(-snr/10);
a=sqrt(noise_power/n);
noise=a*randn(1,n);
s=signal+noise;
s_spect=abs(fft(s));

figure
subplot(2,1,1)
plot(s)
subplot(2,1,2)
plot(s_spect)

for i=1:length(s_spect)/50-10
    s_spect_cum=cum3est(s_spect(i*50:i*50+500),40,500,0,'unbiased',0);
    s_spect_cum1(i)=sum(s_spect_cum);
end   
figure
stem(abs(s_spect_cum1))
%--------------------------------
m=150;
for i=-m:m
    s_cum(:,i+m+1)=cum4est(s,300,1000,60,'unbiased',i,i);
end
s_cum_spect=abs(fft(s_cum));

figure
mesh(s_cum_spect)
bb=sum(s_cum_spect');
figure
plot(bb)
%-----------------------
g=fir1(100,[500*2/length(s_spect),1400*2/length(s_spect)],'bandpass');
s_bandpass=filter(g,1,s);
s_bandpass_spect=abs(fft(s_bandpass));
figure
subplot(2,1,1)
plot(s_bandpass)
subplot(2,1,2)
plot(s_bandpass_spect)
%-----------------------------
delay=500;
mix=s_bandpass(1:n-delay).*s_bandpass(delay+1:n);
mix_spect=abs(fft(mix));

figure
subplot(2,1,1)
plot(mix)
subplot(2,1,2)
plot(mix_spect)