www.pudn.com > carrier.rar > bit_syn.m

clear; 
Rb=5000000/31;%信息数据速率 
lc=31;%一个信息数据扩频成31个码元。扩频增益13dB 
Rc=Rb*lc;%码元速率 
 
L=13;%每个码元里sin信号的周期个数 
fc=Rc*L; %载波频率 
 
Q=4;%每个码元中采样个数 
fs=Rc*Q;%采样频率 
ts=1/fs;%每个取样点的时间间隔 
 
data_number=30;%信息数据的个数 
sample_number=data_number*lc*Q;%采样得到的总的数据个数 
t=0:ts:(sample_number-1)*ts; 
 
%%取均匀分布的随机数据100个，即信息数据 
temp=rand(1,data_number); 
for i=1:data_number 
    if (temp(i)<0.5) 
        data1(i)=-1; 
        data((i-1)*lc*Q+1:i*lc*Q)=-1; 
    else 
        data1(i)=1; 
        data((i-1)*lc*Q+1:i*lc*Q)=1; 
    end 
end 
a=1;%载波的幅度值 
mod_sig=a*data.*cos(2*pi*fc*t);%调制，产生bpsk信号 
%%位同步的初始值 
[lowpass2_B,lowpass2_A1]=cheby2(3,10,0.1);%切比雪夫2型低通滤波器 
lowpass2_A=lowpass2_A1(2:length(lowpass2_A1));%a0为1，所以乘的时候从a1开始乘即可 
data_lowpass2_A=zeros(1,length(lowpass2_A));%经过低通滤波器后的数据 
data_lowpass2_B=zeros(1,length(lowpass2_B)); 
output_lowpass2=0; 
 
m=Q*lc/2; 
N1=2; 
N2=2;  
M1=3; 
 
before_sum=0; 
after_sum=0; 
before_and_after_sum=0; 
bit_before_division=0; 
before_flag=0; 
after_flag=0; 
 
bit2_new=1; 
bit2_old=0; 
bit1_new=0; 
bit1_old=1; 
 
in_phase_integral=0;%同相积分值 
middle_phase_integral=0;%中相积分值 
 
in_phase_hold_new=0; 
middle_phase_hold_new=0; 
 
integral=0; 
jjj=1; 
 
pp=3; 
e_q=mod_sig.*cos(2*pi*fc*t);%乘以相干载波 
e_q=e_q(pp:length(e_q));%去掉前面2点 
%画图 
figure; 
subplot(2,1,1); 
plot(e_q); 
subplot(2,1,2); 
plot(filter(lowpass2_B,lowpass2_A1,e_q)); 
%%%%%%%%%%%%%%%% 
for i=1:length(mod_sig)-11; %%位同步信号的恢复     
     
    %通过切比雪夫低通滤波器，滤除高频分量 
    data_lowpass2_B(1:length(lowpass2_B)-1)=data_lowpass2_B(2:length(lowpass2_B));%去掉前面1点 
    data_lowpass2_A(1:length(lowpass2_A)-1)=data_lowpass2_A(2:length(lowpass2_A));%去掉前面1点 
    data_lowpass2_B(length(lowpass2_B))=e_q(i); 
    data_lowpass2_A(length(lowpass2_A))=output_lowpass2; 
    output_lowpass2=sum(data_lowpass2_B(length(lowpass2_B):-1:1).*lowpass2_B)-sum(data_lowpass2_A(length(lowpass2_A):-1:1).*lowpass2_A);%差分方程的实现 
 
    shuchu(i)=output_lowpass2; 
    %判决，得到0、1方波序列 
    if output_lowpass2>0 
        output_lowpass2_reshape=1; 
    else 
        output_lowpass2_reshape=0; 
    end    
     
    bit_input(i)=output_lowpass2_reshape; 
 
    in_phase_hold_old=in_phase_hold_new; 
    if bit2_new-bit2_old==1 
        if in_phase_integral>0 
            in_phase_hold_new=1; 
        else 
            in_phase_hold_new=0; 
        end 
        in_phase_integral=0; 
    end 
         
    if bit1_new-bit1_old==1 
        if middle_phase_integral>0 
            middle_phase_hold_new=1; 
        else 
            middle_phase_hold_new=0; 
        end 
        middle_phase_integral=0; 
    end 
     
    shuchu1(i)=bit1_new; 
    shuchu2(i)=bit2_new;    
     
    bit1_old=bit1_new; 
    bit2_old=bit2_new; 
     
    in_phase_integral=in_phase_integral+bit_input(i); 
    middle_phase_integral=middle_phase_integral+bit_input(i); 
     
    in_phase_hold_diff=in_phase_hold_new-in_phase_hold_old; 
    middle_phase_hold_xor_in=xor(in_phase_hold_new,middle_phase_hold_new); 
     
    before=in_phase_hold_diff*middle_phase_hold_xor_in; 
    after=in_phase_hold_diff*not(middle_phase_hold_xor_in); 
     
    if before==1 
        before_sum=before_sum+1; 
        before_and_after_sum=before_and_after_sum+1; 
    end 
    if after==1 
        after_sum=after_sum+1; 
        before_and_after_sum=before_and_after_sum+1; 
    end 
    if before_sum==N1 
        before_sum=0; 
        after_sum=0; 
        before_and_after_sum=0; 
        bit_before_division=bit_before_division-1;%调整长度 
    end 
    if after_sum==N1 
        before_sum=0; 
        after_sum=0; 
        before_and_after_sum=0; 
        bit_before_division=bit_before_division+1;%调整长度 
    end 
    if before_and_after_sum==M1 
        before_sum=0; 
        after_sum=0; 
        before_and_after_sum=0; 
    end 
     
    bit_before_division=bit_before_division+1; 
    jlz(i)=bit_before_division; 
     
    if bit_before_division>=m %分频 
        bit1_new=~bit1_old; 
        bit2_new=~bit2_old; 
        bit_before_division=rem(bit_before_division,m); 
    else 
        bit1_new=bit1_old; 
        bit2_new=bit2_old; 
    end 
    bit_syn(i)=bit1_new-bit1_old;%找下跳边沿 
    if bit_syn(i)==-1 
        if integral>Q*lc/2 
            output_data(jjj)=1; 
        else 
            output_data(jjj)=-1; 
        end 
        integral=0; 
        jjj=jjj+1; 
    end 
    integral=integral+output_lowpass2_reshape;        
end 
%画图 
figure 
subplot(2,1,1) 
stem(data(pp:length(data))) 
subplot(2,1,2) 
stem(shuchu2)