clear?all;clc;clear;
tic?
%-------------------------signal?generate---------------------------------%
Fs?????????=?5120;
Fc?????????=?200;?%?Carrier?frequency?in?Hz??
t??????????=?[1:512]‘/Fs;?%?Sampling?times?for?.1?second
x??????????=?sin（20*pi*t）‘;?%?Representation?of?the?signal?
y??????????=?ammod（xFcFs）;?%?Modulate?x?to?produce?y.

%?figure;
%?subplot（211）;?plot（tx）;title（‘Representation?of?the?signal‘）;?%?Plot?x?on?top.
%?subplot（212）;?plot（ty）;title（‘Modulate?x?to?produce?y‘）;?%?Plot?y?below.
%-------------------------end---------------------------------------------%
%-------------------------add?AWGN-----------------------------------------%
N??????????????=length（y）;
y_power????????=var（y）;
y??????????????=y/sqrt（y_power）;
signalPower????=1;
SNR_dB?????????=5;??
SNR????????????=10^（SNR_dB/10）;??
noise_Power????=signalPower/SNR;???%noise?power
noise??????????=sqrt（noise_Power/2）*randn（1N）;%AWGN
signal?????????=y+noise;
%-------------------------end---------------------------------------------%
%-------------------------calculate?cyclic?spectal------------------------%
alpha_len??????=（-0.5:1/N:0.5-1/N）;
M??????????????=N/64;?%window?length
X??????????????=fft（signal）;
X??????????????=fftshift（X）;
f??????????????=-Fs/2:Fs/（N-1）:Fs/2;
%?plot（fabs（X））;
%-------------------------calculate?cyclic?spectal（1/4?cyclic?spectal，need?to?spread）-----------------------------------------%
for?alpha=1:N/2-M/2+1
????for?f1=1:N/2-M/2+2-alpha
????????if?f1==1?
????????????tmp（alphaf1）=X（[f1+N/2+alpha-1-M/2:f1+N/2+alpha-2+M/2]）*（X