clear all;
close all;
clc
Ts = 1;%码元速率
N_sample = 100; %采样速率
dt = Ts / N_sample;
N = 10000; %码元个数
t = 0 : dt : (N * N_sample - 1) * dt;
RAN = randi([0,1],1,N); % 随机0 1序列
gt1 = ones(1,N_sample);
code = [];
RAN0 = RAN;
Progressbar=waitbar(0,'Please wait(1/2)...');%创建进度条
for i = 1 : N
waitbar(i/N);
if(RAN0(i) == 0)
RAN0(i) = -1;
end
code = [code RAN0(i)*gt1]; %采样后码元
end
close(Progressbar);
fc = 5;
CarrierWave = sin(2*pi*fc*t); %载波信号
BPSK_Wave = code.* CarrierWave; %调制
fft_code1 = fftshift(fft(BPSK_Wave)); % 求序列的频谱
PE1 = 10 * log10(abs(fft_code1) .^ 2 / (N * Ts)); % 公式法求功率谱密度
PEL1 = (-length(fft_code1) / 2 : length(fft_code1) / 2 - 1) / N; % 转换成对应频率（-L/2:L/2-1）*fs/L
%%%%%%%%%%%%%% 绘制信号 %%%%%%%%%%%%%%%%%%
figure (1)
subplot(3,1,1);plot(t,code);axis([0,10,-1.5,1.5]);title('码元序列');xlabel('t/s');ylabel('幅度');%码元序列
subplot(3,1,2);plot(t,BPSK_Wave);axis([0,10,-1.5,1.5]);title('BPSK波形');xlabel('t/s');ylabel('幅度');%BPSK波形
subplot(3,1,3);plot(PEL1,PE1);axis([fc-5,fc+5,-100,100]);xlabel('频率/HZ');ylabel('P/dB');title('功率谱密度');%功率谱密度
%%%%%%%%%%%%%%%%%计算误码率 %%%%%%%%%%%%%%%%%%%
Pe = [];
h=waitbar(0,'Please wait(2/2)...');%创建进度条
%%%%%%%%%%%%% 加入高斯噪声 %%%%%%%%%%%%%%%
SNR = -30 : 30;
SNR0 = SNR+10*log10(25);%等效窄带噪声信噪比
for i =1 : length(SNR);
BPSK_Noise = awgn(BPSK_Wave,SNR(i));
waitbar(i/length(SNR));
%%%%%%%%%%%%%%%%%带通滤波器%%%%%%%%%%%%%%%%%%%%%%
BPF = fir1(101,[(fc-1)/(N_sample/2),(fc+1)/(N_sample/2)]);
BPSK_BPF = filter(BPF,1,BPSK_Noise);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%% BPSK信号的解调（相干）%%%%%%%%%%%%%
% BPSK_Demo = BPSK_Noise.* CarrierWave ;%相干解调
% fp = 1; %截至频率2.5hz
% fcm = 2*fp/N_sample; %归一化频率
% LPF = fir1(30,fcm); %反复实验得出阶数
% BPSK_LPF = filter2(LPF,BPSK_Demo); %此处不用conv卷积，因为长度增加
fp = 1;
BPSK_LPF = demodulation(BPSK_Noise,CarrierWave,fp,N_sample); %将带通后解调过程压缩为子函数输出为过低通后波形
%%%%%%%%%%%%%%%% 抽样判决 %%%%%%%%%%%%%%%%%%%
code_back = [];
count = 0;
for q = 1:N*N_sample
if(BPSK_LPF(q) > 0)
code_back = 1;
else
code_back = -1;
end
if (code_back ~= code(q))
count = count + 1;
end
end
error = count / (N*N_sample);
Pe = [Pe error];
end
close(h);
figure (2)
snr = 10.^(0.1.*SNR);
Pe_theor = (erfc(sqrt(snr))).*(1-0.5*erfc(sqrt(snr)));
semilogy(SNR0,Pe,'b');xlabel('SNR/db');ylabel('误码率');hold on;title('BPSK误码率曲线');
semilogy(SNR,Pe_theor,'r');grid on;legend('实际值','理论值');axis([-4,8,10^-4,1])%xlabel('SNR/db');ylabel('误码率/10^x');title('BPSK误码率曲线');
