function?[dalfaNNpf0alfa0SCD]?=?SCD_FAM（IfsdfM）
%?輸入
%?I：信號實(shí)部
%?fs:信號采樣率
%?df：頻率分辨率
%?M?：不確定量

%?輸出
%?dalfa：循環(huán)頻率分辨率
%?N?：觀測時(shí)間內(nèi)離散取樣總數(shù)
%?Np：第一個(gè)FFT的點(diǎn)數(shù)N‘是靠近且大于fs/df的2的冪次方
%?f0：頻率軸
%?alfa0：循環(huán)頻率軸
%?SCD：循環(huán)譜
dalfa?=?df/M;???????????????????????%?循環(huán)頻率分辨率
x?=?I;??????????????????????????????%?實(shí)信號序列
Np?=?pow2（nextpow2（fs/df））;?????????%?第一個(gè)FFT的點(diǎn)數(shù)N‘是靠近且大于fs/df的2的冪次方？???????????????????????????????????
L?=?Np/4;???????????????????????????%?滑動(dòng)因子，為了避免估計(jì)中的混疊現(xiàn)象和循環(huán)泄漏應(yīng)該小于等于四分之一的時(shí)間窗口Np。???????????????????????????????????
P?=?pow2（nextpow2（fs/dalfa/L））;?????%?用一個(gè)P點(diǎn)FFT的傅里葉變換取代計(jì)算復(fù)解調(diào)序列乘積的平均
N?=?P*L;????????????????????????????%?觀測時(shí)間內(nèi)離散取樣總數(shù)

if?length（x）????x（N）?=?0;
elseif?length?（x）>N
????x?=?x（1:N）;????????????????????%觀測時(shí)間內(nèi)離散取樣的總數(shù)
end

NN?=?（P-1）*L+Np;
xx?=?x;
xx（NN）?=?0;
xx?=?xx（:）;
X?=?zeros（NpP）;
for?k?=?0:P-1
????X（:k+1）?=?xx（k*L+1:k*L+Np）;????%將數(shù)據(jù)按時(shí)域滑動(dòng)L點(diǎn)保存大小為窗口的大小Np
end

a?=?hamming?（Np）;
XW?=?diag（a）*X;?%數(shù)據(jù)削度

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%?復(fù)解調(diào)的計(jì)算——第一次Np點(diǎn)FFT的計(jì)算

XF1?=?fft（XW）;????????????????????????%滑動(dòng)Np點(diǎn)FFT
XF1?=?fftshift（XF1）;??????????????????%將fft的主值區(qū)間變換至[-pipi]
XF1?=?[XF1（:P/2+1:P）?XF1（:1:P/2）];??%第9列-16列和第1列-8列交換——f

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

E?=?zeros（NpP）;
for?k?=?-Np/2:Np/2-1?????????????????????????????%分別左右搬移循環(huán)頻率的一半
????for?m?=?0:P-1
????????E（k+Np/2+1?m+1）?=?exp（-i*2*pi*k*m*L/Np）;%頻移量
????end
end
XD?=?XF1.*E;?????????????????????????????????????%對Np點(diǎn)FFT的輸出進(jìn)行頻移
XD?=?conj（XD‘）;??????????????????????????????????%計(jì)算每一小段譜的共軛

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%