jcwz.m

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

for i=1:10
clear

k=15E+10;  %调频斜率
fo=15E+6;%载频
T=40E-6;%脉冲宽度
n=4000;%抽样点数
fs=70E+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=-10;
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)

m=50;
for i=-m:m
    s_cum(:,i+m+1)=cum4est(s,200,1000,60,'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(100,0.1,'low');
bb_low=filter(g,1,bb);
figure
plot(bb_low)

end