BPSK调制仿真代码

BPSK调制仿真代码，包含了信号生成、调制、信道传输和解调的全过程。

%% BPSK调制解调仿真clear all;close all;clc;%% 1. 参数设置N=10000;% 比特数Rb=1000;% 比特率 (bps)fc=10e3;% 载波频率 (10kHz)fs=10*fc;% 采样频率Tb=1/Rb;% 比特周期Ts=1/fs;% 采样周期samples_per_bit=fs/Rb;% 每比特采样数t_bit=0:Ts:Tb-Ts;% 一个比特周期的时间向量% SNR范围 (dB)EbN0_dB=0:2:10;EbN0=10.^(EbN0_dB/10);% 线性值%% 2. 生成随机比特序列bits=randi([0,1],1,N);fprintf('生成 %d 个随机比特\n',N);%% 3. BPSK调制% BPSK映射: 0 -> +1, 1 -> -1bpsk_symbols=2*bits-1;% 将[0,1]映射到[+1,-1]% 生成基带信号（矩形脉冲成型）baseband_signal=zeros(1,N*samples_per_bit);fori=1:Nbaseband_signal((i-1)*samples_per_bit+1:i*samples_per_bit)=bpsk_symbols(i);end% 生成载波t_total=0:Ts:N*Tb-Ts;carrier=cos(2*pi*fc*t_total);% BPSK调制信号（上变频）modulated_signal=baseband_signal.*carrier;%% 4. 仿真不同信噪比下的性能ber_simulated=zeros(size(EbN0_dB));ber_theoretical=zeros(size(EbN0_dB));forsnr_idx=1:length(EbN0_dB)fprintf('\n仿真 Eb/N0 = %d dB ...\n',EbN0_dB(snr_idx));%% 4.1 添加AWGN噪声% 计算信号功率signal_power=sum(abs(modulated_signal).^2)/length(modulated_signal);% 计算噪声功率（考虑带通信号）Eb=signal_power*Tb;% 每比特能量N0=Eb/EbN0(snr_idx);% 噪声功率谱密度noise_power=N0*fs/2;% 噪声功率（双边带）% 生成高斯白噪声noise=sqrt(noise_power)*randn(size(modulated_signal));% 添加噪声到调制信号received_signal=modulated_signal+noise;%% 4.2 BPSK相干解调% 下变频（乘以同频同相的载波）demod_signal=received_signal.*carrier;% 低通滤波（积分清零）recovered_symbols=zeros(1,N);fori=1:N start_idx=(i-1)*samples_per_bit+1;end_idx=i*samples_per_bit;% 积分运算recovered_symbols(i)=sum(demod_signal(start_idx:end_idx));end% 判决recovered_bits=recovered_symbols<0;% 负值判为1，正值判为0%% 4.3 计算误码率errors=sum(bits~=recovered_bits);ber_simulated(snr_idx)=errors/N;% 理论误码率（BPSK在AWGN信道）ber_theoretical(snr_idx)=0.5*erfc(sqrt(EbN0(snr_idx)));fprintf('误码数: %d, 误码率: %.6f\n',errors,ber_simulated(snr_idx));end%% 5. 可视化结果figure('Position',[100,100,1200,800]);% 5.1 原始比特序列subplot(3,3,1);stem(bits(1:20),'filled','LineWidth',1.5);title('原始比特序列 (前20个比特)');xlabel('比特序号');ylabel('幅度');grid on;ylim([-0.21.2]);% 5.2 BPSK符号subplot(3,3,2);stem(bpsk_symbols(1:20),'filled','LineWidth',1.5);title('BPSK调制符号 (0->+1, 1->-1)');xlabel('符号序号');ylabel('幅度');grid on;ylim([-1.51.5]);% 5.3 基带信号波形subplot(3,3,3);plot((1:5*samples_per_bit)*Ts,baseband_signal(1:5*samples_per_bit),'LineWidth',1.5);title('基带信号波形 (前5个比特)');xlabel('时间 (s)');ylabel('幅度');grid on;% 5.4 载波信号subplot(3,3,4);plot(t_total(1:500),carrier(1:500),'LineWidth',1.5);title('载波信号 (部分波形)');xlabel('时间 (s)');ylabel('幅度');grid on;% 5.5 调制信号subplot(3,3,5);plot(t_total(1:5*samples_per_bit),modulated_signal(1:5*samples_per_bit),'LineWidth',1.5);title('BPSK调制信号 (前5个比特)');xlabel('时间 (s)');ylabel('幅度');grid on;% 5.6 频谱分析subplot(3,3,6);% 基带信号频谱[P_baseband,f_baseband]=pwelch(baseband_signal,[],[],[],fs);% 调制信号频谱[P_mod,f_mod]=pwelch(modulated_signal,[],[],[],fs);plot(f_baseband/1000,10*log10(P_baseband),'b','LineWidth',1.5);hold on;plot(f_mod/1000,10*log10(P_mod),'r','LineWidth',1.5);title('信号频谱');xlabel('频率 (kHz)');ylabel('功率谱密度 (dB/Hz)');legend('基带信号','调制信号');grid on;xlim([0,20]);% 5.7 接收信号（加噪声后）subplot(3,3,7);plot(t_total(1:5*samples_per_bit),received_signal(1:5*samples_per_bit),'LineWidth',1.5);title('接收信号 (Eb/N0 = 10dB, 前5个比特)');xlabel('时间 (s)');ylabel('幅度');grid on;% 5.8 解调后的信号subplot(3,3,8);plot(t_total(1:5*samples_per_bit),demod_signal(1:5*samples_per_bit),'LineWidth',1.5);title('解调信号 (下变频后)');xlabel('时间 (s)');ylabel('幅度');grid on;% 5.9 误码率曲线subplot(3,3,9);semilogy(EbN0_dB,ber_simulated,'bo-','LineWidth',2,'MarkerSize',8,'MarkerFaceColor','b');hold on;semilogy(EbN0_dB,ber_theoretical,'r--','LineWidth',2);title('BPSK系统误码率性能');xlabel('Eb/N0 (dB)');ylabel('误码率 (BER)');legend('仿真结果','理论曲线','Location','best');grid on;% 星座图（Eb/N0=10dB时的最后1000个符号）figure('Position',[100,100,600,500]);last_N=min(1000,N);scatter(real(recovered_symbols(end-last_N+1:end)),imag(recovered_symbols(end-last_N+1:end)),30,'filled');title('BPSK星座图 (Eb/N0=10dB)');xlabel('同相分量 (I)');ylabel('正交分量 (Q)');grid on;axis equal;xlim([-3,3]);ylim([-3,3]);hold on;plot([0,0],[-3,3],'k--',[-3,3],[0,0],'k--');% 眼图figure('Position',[100,100,800,400]);% 使用低通滤波后的信号生成眼图eye_diagram_signal=demod_signal;% 这里使用解调后的信号samples_per_eye=2*samples_per_bit;% 显示2个比特周期的眼图subplot(1,2,1);hold on;fori=1:min(50,N-1)start_idx=(i-1)*samples_per_bit+1;end_idx=start_idx+samples_per_eye-1;ifend_idx<=length(eye_diagram_signal)t_eye=(0:samples_per_eye-1)*Ts;plot(t_eye*1000,eye_diagram_signal(start_idx:end_idx),'b');endendtitle('BPSK解调信号眼图');xlabel('时间 (ms)');ylabel('幅度');grid on;subplot(1,2,2);% 平均眼图num_eyes=min(100,floor(length(eye_diagram_signal)/samples_per_bit)-1);eye_matrix=zeros(num_eyes,samples_per_eye);fori=1:num_eyes start_idx=(i-1)*samples_per_bit+1;end_idx=start_idx+samples_per_eye-1;eye_matrix(i,:)=eye_diagram_signal(start_idx:end_idx);endeye_mean=mean(eye_matrix,1);t_eye=(0:samples_per_eye-1)*Ts;plot(t_eye*1000,eye_mean,'r','LineWidth',2);title('平均眼图');xlabel('时间 (ms)');ylabel('幅度');grid on;%% 6. 显示关键结果fprintf('\n========== BPSK调制仿真结果 ==========\n');fprintf('比特数: %d\n',N);fprintf('比特率: %d bps\n',Rb);fprintf('载波频率: %.1f kHz\n',fc/1000);fprintf('采样频率: %.1f kHz\n',fs/1000);fprintf('每比特采样数: %d\n',samples_per_bit);fprintf('\n');fprintf('误码率比较:\n');fprintf('Eb/N0(dB)\t仿真BER\t理论BER\n');fori=1:length(EbN0_dB)fprintf(' %2d\t\t%.2e\t%.2e\n',EbN0_dB(i),ber_simulated(i),ber_theoretical(i));end