Matlab实现二进制DPSK调制及差分相干解调 上传版本.zip

clear all; Ts = 1; %码元周期 N_sample = 1000; %每个码元抽样点数 fs=N_sample; %抽样频率 fc = 5; %载波频率 dt = Ts/N_sample; %抽样的时间间隔 N = 200; %码元数 t = 0:dt:(N*N_sample-1)*dt; df = fs/length(t); f = -fs/2:df:fs/2-df; %定义频率矢量（频谱图的横坐标） % 基本码元 g(t) = 1 gt0 = zeros(1,N_sample); gt1 = ones(1,N_sample); %单极性不归零 %生成随机码元 random_code = randi([0,1],1,N); %单极性波形的最后结果 yt1 = zeros(1,N*N_sample-1); %绝对码 yt2 = zeros(1,N*N_sample-1); %相对码 last = 0; %参考码元 for i = 1:N if random_code(i) == 1 %得到波形图 yt1((i-1)*N_sample+1:i*N_sample) = gt1; %单极性不归零NRZ波形 %绝对码 if last == 0 yt2((i-1)*N_sample+1:i*N_sample) = gt1; last=1; else yt2((i-1)*N_sample+1:i*N_sample) = gt0; last=0; end else yt1((i-1)*N_sample+1:i*N_sample) = gt0; %绝对码 if last == 0 yt2((i-1)*N_sample+1:i*N_sample) = gt0; last=0; else yt2((i-1)*N_sample+1:i*N_sample) = gt1; last=1; end end end %********************************************************************* %1 %求单极性不归零时域波形于波功率谱密度，进行2ASK调制 figure(1) subplot(211) plot(t,yt1); axis([0 12 -0.1 1.1]); title('绝对码基带信号'); xlabel('时间t/s'); grid; subplot(212) plot(t,yt2); axis([0 12 -0.1 1.1]); title('相对码基带信号'); xlabel('时间t/s'); grid; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %2 c1=sin(2*pi*fc*t); c2=-c1; for i=1:length(t) if yt2(i) == 0 yt2_mod(i) = c1(i); else yt2_mod(i) = c2(i); end end figure(2) subplot(211) plot(t,yt2); axis([0 12 -0.1 1.1]); title('相对码基带信号'); xlabel('时间t/s'); grid; subplot(212) plot(t,yt2_mod); axis([0 12 -1.1 1.1]); title('DPSK调制信号'); xlabel('时间t/s'); grid; %功率谱密度 figure(3) subplot(211) fmt=fft(yt2); % 对时域信号进行FFT变换，计算其频谱 fmt=fftshift(fmt); fmt=abs(fmt); fmt_dB=fmt.^2/Ts; maxF=max(fmt_dB); fmt_dB=fmt_dB/maxF; fmt_dB= 10*log10(fmt_dB +eps); plot(f,fmt_dB);grid on; axis([-5 5 -150 0]); xlabel('频率(Hz)');ylabel('功率谱幅度值(dB)'); title('二进制相对码信号功率谱密度(db)'); subplot(212) fmt1=fft(yt2_mod); % 对时域信号进行FFT变换，计算其频谱 fmt1=fftshift(fmt1); fmt1=abs(fmt1); fmt_dB1=fmt1.^2/Ts; maxF1=max(fmt_dB1); fmt_dB1=fmt_dB1/maxF1; fmt_dB1= 10*log10(fmt_dB1 +eps); plot(f,fmt_dB1);grid on; axis([-25 25 -150 20]); xlabel('频率(Hz)');ylabel('功率谱幅度值(dB)'); title('2DPSK调制信号功率谱密度(db)'); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %3 figure(4) yt2_mod_awgn = awgn(yt2_mod,10,'measured'); subplot(211) plot(t,yt2_mod); axis([0 12 -1.1 1.1]); title('DPSK调制信号'); xlabel('时间t/s'); grid; subplot(212) plot(t,yt2_mod_awgn); axis([0 12 -2 2]); title('叠加噪声后DPSK调制信号'); xlabel('时间t/s'); grid; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %4 %延时1个周期的DPSK信号 st1 = c1; st1 = awgn(st1,10,'measured'); for i=1+1*N_sample:length(yt2_mod_awgn) st1(i) = yt2_mod_awgn(i-1*N_sample); end figure(5) subplot(211) plot(t,yt2_mod_awgn); axis([0 12 -2 2]); title('叠加噪声后DPSK调制信号'); xlabel('时间t/s'); grid; subplot(212) plot(t,st1); axis([0 12 -2 2]); title('加噪DPSK调制信号延时一个码元周期的波形图'); xlabel('时间t/s'); grid; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %5 差分相干解调 figure(6) subplot(211) yt2_demod = yt2_mod_awgn.*st1; plot(t,yt2_demod); axis([0 12 -1.5 1.5]); title('2DPSK差分相干解调信号波形图'); xlabel('时间t/s'); grid on; subplot(212) fmt2=fft(yt2_demod); % 对时域信号进行FFT变换，计算其频谱 fmt2=fftshift(fmt2); plot(f,abs(fmt2));grid on; axis([-25 25 0 13000]); xlabel('频率(Hz)');ylabel('功率谱幅度值(dB)'); title('2DPSK差分相干调制信号幅频特性'); grid on; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %6 % 进行低通滤波 figure(6) subplot(211) fpass = 0; fstop = 5; [f1,spf1] = IdealFilter(length(t),fs,fpass,fstop,fft(yt2_demod)); % 此处的频谱不能用fftshift后的！！！！！ spf_t1 = ifft(spf1); plot(t,spf_t1);grid on; axis([0 12 -0.7 0.7]); xlabel('时间(s)');ylabel('电压值(V)'); title('2DPSK相干解调理想低通滤波后信号波形图'); subplot(212) fmt3=fft(spf_t1); % 对时域信号进行FFT变换，计算其频谱 fmt3=fftshift(fmt3); plot(f,abs(fmt3));grid on; axis([-15 15 0 13000]); xlabel('频率(Hz)');ylabel('功率谱幅度值(dB)'); title('2DPSK相干解调信号的理想低通滤波结果'); grid on; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %7 %抽样判决 r=zeros(1,N_sample*N); for i = 1:N-1 if spf_t1((i-0.5)*N_sample) > 0 %得到波形图 r((i-0.5)*N_sample+1:(i+0.5)*N_sample) = gt0; %单极性不归零NRZ波形 else r((i-0.5)*N_sample+1:(i+0.5)*N_sample) = gt1; end end figure(7) subplot(211) plot(t,yt1); axis([0 12 -0.1 1.1]); title('发送端的基带信号波形图'); xlabel('时间t/s'); grid; subplot(212) plot(t,r); axis([0 12 -0.1 1.1]); title('接收采样判决后的被调制信号波形图'); xlabel('时间t/s'); grid;