function?[Y]=DSSS（Xmode）
%完成DSSS調(diào)制功能
%mode=[12].?1進(jìn)行調(diào)制，2進(jìn)行解調(diào)，未指定時(shí)自動(dòng)完成調(diào)制和解調(diào)兩個(gè)功能
switch?nargin
????case?0
????????X=‘This?is?a?test.‘;
?????????Y=DSSS（X）;
????????return
????case?1
????????Y1=DSSS（X?1）;
????????Y2=DSSS（Y1?2）;
????????Y=Y2;
????????return
????case?2
????????if?mode==1%調(diào)制
????????????D=ones（17）;
????????????m_sequence=Msequence（D）;
????????????X_length=length（X）;
????????????ascii_value=abs（X）;
????????????ascii_binary=zeros（X_length7）;
????????????%將數(shù)據(jù)轉(zhuǎn)換為ASCII二進(jìn)制碼
????????????for?ii=1:X_length
????????????????ascii_binary（ii:）=Binary（ascii_value（ii））;
????????????end
????????????figure（1）;subplot（211）;plot（reshape（ascii_binary1X_length*7））;title（‘A:輸入數(shù)據(jù)‘）;grid?on;
????????????%擴(kuò)頻
????????????Sp_expand=zeros（X_length127*7）;
????????????for?ii=1:X_length
????????????????for?jj=1:7
????????????????????Sp_expand（ii127*jj-126:127*jj）=xor（m_sequenceascii_binary（iijj））;
????????????????end
????????????end
????????????figure（2）;plot（reshape（Sp_expand1X_length*127*7））;title（‘B:數(shù)據(jù)擴(kuò)展‘）;
????????????%將擴(kuò)頻碼轉(zhuǎn)換為BPSK（1，-1）序列
????????????for?ii=1:X_length
????????????????for?jj=1:127*7
????????????????????if~（Sp_expand（iijj））
????????????????????????Sp_expand（iijj）=-1;
????????????????????end
????????????????end
????????????end
????????????Sp_expand_bpsk=reshape（Sp_expand1X_length*127*7）;
????????????figure（3）;plot（Sp_expand_bpsk）;title（‘C:BPSK調(diào)制‘）;
????????????Y=Sp_expand_bpsk;
????????elseif?mode==2%解調(diào)
????????????D=ones（17）;
????????????m_sequence=Msequence（D）;
????????????%將BPSK雙極性轉(zhuǎn)換為單極性
????????????l=length（X）/（127*7）;
????????????X_length=length（X）;
????????????for?ii=1:X_length
????????????????if?X（ii）==-1
????????????????????X（ii）=0;
????????????????end
????????????end
????????????Sp_expand=