www.gusucode.com > ​认知无线电频谱检测技术的研究,有循环检测，周期性检测源码程序 > 程序/zhouqi.m

    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%生成bpsk调制信号
fs=100;
%采样频率
fc=40;
%载频
fo=fs/20;
%码率
a=2*fo;
%循环周期
T=40;
%信号样本
x=rand(40,1);
y=round(x);
a1=y*2-1;
z=ones(200,1);
for i=1:40
    for j=1:5
        an(5*i-5+j)=z(5*i-5+j)*a1(i);
    end
end
t=1/fs:1/fs:2;
xn=an.*cos(4*pi*fc*t);
figure(1)
plot(t,xn);
axis([0 2 -1.5 1.5]);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%进行周期图检测
window=kaiser(length(xn),0.5);
%矩形窗
nfft=512;
%512fft
[Pxx,f]=periodogram(xn,window,nfft,fs);
%周期图检测
%%%%%%%%%(生成一段加噪信号）
as=rand(20,1);
b=as*2;
c=floor(b);
d=reshape(c,10,2);
e=bi2de(d,'left-msb');
h=modem.qammod(4);
g=modulate(h,e);
scatterplot(g);
%生成一段随机4QAM信号
N=length(g);
x=real(g);
y=imag(g);
fc=40;
%载波频率，有线电视信号
t0=0.000001;
ts=1e-010;
t1=0:ts:t0;
n1=0.1*randn(1,N);
for i=1:N
   s1=x(i)*cos(2*pi*fc*t1)-y(i)*sin(2*pi*fc*t1);
end
%生成4QAM调制后信号
%加入噪声nt
t2=0.000001:1e-010:0.000002;
M1=length(t2);
nt=0.1*randn(1,M1);
s2=nt.*cos(2*pi*fc*t2);
%add nt
t=0:ts:0.000002;
s=zeros(1,20001);
for i=1:10001
    s(i)=s1(i);
end
for j=1:10000
    s(j+10000)=s2(j);
end
%加入间隔无信号时间
%生成调制后信号
%%%%%%%%%%%%%%%%%%%%%%（1）取有用信号时间段，计算函数值
cl=xcorr(s1);
L=length(cl);
i2=1:2:L;
c2=cl(i2);
%自相关函数
a1=fc;
%循环周期
%构造积分对象pp
p=exp(-2*pi*t1*j);
M=length(p);
pp=c2.*p;
%进行无穷大积分
ts=1e-010;
cxx1=pp*ts;
u1=sum(cxx1(1:10),'double');
%加入统计频率周期a2
N1=length(c2);
N2=length(t);
f1=60e6;
%采样时间
Te=0.03;
i3=1:N1;
a2=i3./(N1*Te);
tj1=exp(a2);
cx1=tj1*u1*1e10;
U1=sum(cx1(1:10));
%%%%%%%%%%%%%%%%%%%%%%（2）取噪声时间段，计算函数值
cl2=xcorr(s2);
L=length(cl2);
i3=1:2:L;
c22=cl2(i3);
p2=exp(-2*pi*t2*j);
M2=length(p);
pp2=c22.*p2;
%进行无穷大积分
ts=1e-010;
cxx2=pp2*ts;
u2=sum(cxx2(1:10),'double');
%加入统计频率周期a2
i3=1:N1;
a2=i3./(N1*Te);
tj2=exp(a2);
cx2=tj2*u2*1e10;
U2=sum(cx2(1:10));
%检测完毕
%%%%%%%%%%%%%%%%%%% 输出检测示意图;
tz=0:ts:0.000002;
sz=zeros(1,20001);
for i=1:10001
    sz(i)=U1;
end
for j=1:10000
    sz(j+10000)=U2;
end
%%%%%%%%（检测完成，输出图谱）
figure(2)
plot(f,-10*log10(Pxx));
window=kaiser(length(xn),0.5);
nfft=1024;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%1024fft
[Pxx,f]=periodogram(xn,window,nfft,fs);
%周期图检测
figure(3)
plot(f,-10*log10(Pxx));
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%对不同类型窗函数进行检测性能分析
window1=boxcar(length(xn));
%矩形窗
window2=hamming(length(xn));
%海明窗
window3=blackman(length(xn));
%blackman窗
[Pxx1,f]=periodogram(xn,window1,nfft,fs);
[Pxx2,f]=periodogram(xn,window2,nfft,fs);
[Pxx3,f]=periodogram(xn,window3,nfft,fs);
figure(4)
subplot(221)
plot(f,-10*log10(Pxx));
subplot(222)
plot(f,-10*log10(Pxx1));
subplot(223)
plot(f,-10*log10(Pxx2));
subplot(224)
plot(f,-10*log10(Pxx3));