dpsk2.zip_2dpsk

%- 2DPSK 调制与解调 %--------------------------------------------------- %>>>>>>>>>>>>>>>>>>Initial_Part>>>>>>>>>>>>>>>>>>>>> %--------------------------------------------------- function y=dpsk2() fs =72000000; Time_Hold_On = 1/24000; Num_Unit = fs * Time_Hold_On; High_Level = ones ( 1, Num_Unit ); Low_Level = zeros ( 1, Num_Unit ); w = 250000; A = 1; %--------------------------------------------------- %>>>>>>>>>>>>>>>>>>Initial_The_Signal>>>>>>>>>>>>>>> %--------------------------------------------------- Sign_Set = [1,0,0,1,0,0,1,0] Lenth_Of_Sign = length ( Sign_Set ); st = zeros ( 1, Num_Unit * Lenth_Of_Sign ); sign_orign = zeros ( 1, Num_Unit * Lenth_Of_Sign ); sign_result = zeros ( 1, Num_Unit * Lenth_Of_Sign ); t = 0 : 1/fs : Time_Hold_On * Lenth_Of_Sign - 1/fs; %--------------------------------------------------- %>>>>>>>>>>>Generate_The_Original_Signal>>>>>>>>>>>> %--------------------------------------------------- for I = 1 : Lenth_Of_Sign if Sign_Set(I) == 1 sign_orign( (I-1)*Num_Unit + 1 : I*Num_Unit) = High_Level; else sign_orign( (I-1)*Num_Unit + 1 : I*Num_Unit) = Low_Level; end end %--------------------------------------------------- %>>>>>>>>>>>>>>>>>>Modulation_Part>>>>>>>>>>>>>>>>>> %--------------------------------------------------- for I = 1 : Lenth_Of_Sign if Sign_Set(I) == 1 st( (I-1)*Num_Unit + 1 : I*Num_Unit) = A * cos ( 2 * pi * w * t( (I-1)*Num_Unit + 1 : I*Num_Unit ) + ( pi / 2 ) ); else st( (I-1)*Num_Unit + 1 : I*Num_Unit) = A * cos ( 2 * pi * w * t( (I-1)*Num_Unit + 1 : I*Num_Unit ) ); end end figure(1) subplot ( 2, 1, 1 ) plot(t, sign_orign); axis( [ 0 , Time_Hold_On *( Lenth_Of_Sign + 1), - (A / 2), A + (A / 2) ] ); title ( '原始信号' ); grid subplot ( 2, 1, 2 ); plot ( t, st ); axis( [ 0 , Time_Hold_On *( Lenth_Of_Sign + 1), - 3*(A / 2), 3*(A / 2) ] ); title ( '调制后的信号' ); grid %--------------------------------------------------- %>>>>>>>>>>>>>>>>>>相乘>>>>>>>>>>>>>>>>>>>>>>>>>>>>> %--------------------------------------------------- dt = st .* cos ( 2 * pi * w * t ); figure(2) subplot(3,1,1) plot ( t, dt ); axis( [ 0 , Time_Hold_On *( Lenth_Of_Sign + 1), - 3*(A / 2), 3*(A / 2) ] ); title ( '相乘后的波形' ); grid %%频域分析 f1=600000;N2=2^13; n2=0:N2-1;t2=n2/f1; DT=fft(dt,N2);mag=abs(DT); f3=n2*f1/N2; figure(3) subplot(211); plot(f3(1:N2/2),mag(1:N2/2)) title('相乘后频谱') %%-------- figure(2) subplot(3,1,2) dt=awgn(dt,1) ; plot(dt); title('加入高斯白噪声后波形') %--------------------------------------------------- %>>>>>>>>>>>>>>>>>>>低通滤波部分>>>>>>>>>>>>>>>>>>>> %--------------------------------------------------- [N,Wn] = buttord( 2*pi*150000, 2*pi*250000,3,30,'s'); %临界频率采用角频率表示 [b,a]=butter(N,Wn,'s'); [bz,az]=impinvar(b,a,fs); %映射为数字的 dt = filter(bz,az,dt); subplot(3,1,3) plot ( t, dt ); axis( [ 0 , Time_Hold_On *( Lenth_Of_Sign + 1), - 3*(A / 2), 3*(A / 2) ] ); title ( '低通滤波后的波形' ); grid figure(3) %%频域分析-------------------- DT=fft(dt,N2);mag=abs(DT); f5=n2*f1/N2; subplot(212); plot(f5(1:N2/2),mag(1:N2/2)); title('低通滤波后频谱') %--------------------------------------------------- %>>>>>>>>>>>>>抽样判决 & 逆码变换部分>>>>>>>>>>>>>>> %--------------------------------------------------- for I = 1 : Lenth_Of_Sign if dt((2*I-1)*Num_Unit/2) < 0.25 sign_result( (I-1)*Num_Unit + 1 : I*Num_Unit) = High_Level; else sign_result( (I-1)*Num_Unit + 1 : I*Num_Unit) = Low_Level; end end figure(4) plot ( t, sign_result ); axis( [ 0 , Time_Hold_On *( Lenth_Of_Sign + 1), - 2*(A / 2), 3*(A / 2) ] ); title ( '逆码变换后的波形' ); grid