FSK.rar_PCM编码 调制_fsk编码_调制 2ask fsk

clear;clc; close all; %% 系统仿真参数 A = 1; %载波信号振幅 fc = 2; %载波信号频率 snr = 15; %信噪比 N_Sample = 8; %基带信号中每个码元的采样点数 N = 10000; %码元个数 Ts = 1; %码元宽度 df = 0.001; %频率分辨率 B = 1/Ts; %码元带宽 f_start = fc - B; %滤波器起始频率 f_cutoff = fc + B; %滤波器截止频率 fs = fc * N_Sample; %系统采样频率，即考虑载波后，一个码元内的采样点数 ts = Ts/fs; %系统采样间隔 t = 0:ts:N*Ts-ts; Lt = length(t); %% 调制信号及其功率谱密度 %% 单极性不归零信号 figure(1); d = sign(randn(1,N)); dd = sigexpand((d+1)/2,fc*N_Sample); gt = ones(1,fc*N_Sample);%NRZ波形 d_NRZ = conv(dd,gt); d_NRZ1 = d_NRZ(1:Lt); %% 双极性不归零信号 d_sjx = 2 * d_NRZ - 1; d_sjx1 = d_sjx(1:Lt); subplot(221); plot(t,d_NRZ1); axis([min(t),10,min(d_NRZ)-0.2,max(d_NRZ)+0.2]); xlabel('t');title('单极性NRZ信号'); subplot(222); [d_NRZ1f,d_NRZ1,df1,f] = T2F_new(d_NRZ1,ts,df,fs); plot(f,10*log10(abs(fftshift(d_NRZ1f).^2/length(f)))); axis([-5*B,5*B,-50,0]); xlabel('f');title('单极性NRZ信号功率谱密度'); %% 2FSK s_2fsk = A * cos(2*pi*fc*t+2*pi*d_sjx(1:Lt).*t);%生成2FSK信号 subplot(223); plot(t,s_2fsk); axis([min(t),10,min(s_2fsk)-0.2,max(s_2fsk)+0.2]); xlabel('t');title('2FSK信号'); subplot(224); [s_2fskf,s_2fsk,df1,f] = T2F_new(s_2fsk,ts,df,fs); plot(f,10*log10(abs(fftshift(s_2fskf).^2/length(f)))); axis([-fc-3*B,fc+3*B,-50,0]); xlabel('f');title('2FSK信号功率谱密度'); %% 生成信道加性高斯白噪声 snr_lin = 10^(snr/10); signal_energy = 0.5 * A^2 * Ts;%接收信号的平均能量 noise_power = (signal_energy * fs) / (snr_lin * 4);%求出噪声方差（噪声均值为0） noise_std = sqrt(noise_power);%求出噪声均方差 noise = noise_std .* randn(1,Lt);%以噪声均方差作为幅度产生高斯白噪声 figure(2); subplot(221); plot(t,noise(1:Lt)); xlabel('t');title('信道噪声'); axis([min(t),10,min(noise)-1,max(noise)+1]); [noisef,noise,df1,f] = T2F_new(noise,ts,df,fs); subplot(222); plot(f,10*log10(abs(fftshift(noisef).^2/length(f)))); axis([-fc-3*B,fc+3*B,-50,0]); xlabel('f');title('信道噪声功率谱密度'); %% 将2FSK信号送入信道 r = s_2fsk(1:Lt) + noise(1:Lt);%叠加了噪声的已调信号，相当于将已调信号送入理想信道 subplot(223); plot(t,r);%画出叠加噪声后的已调2FSK信号 xlabel('t');title('加燥2FSK信号'); axis([min(t),10,min(r),max(r)]); [rf,r,df1,f] = T2F_new(r,ts,df,fs); subplot(224); plot(f,10*log10(abs(fftshift(rf).^2/length(f)))); axis([-fc-3*B,fc+3*B,-50,0]); xlabel('f');title('加燥2FSK信号功率谱密度'); figure(3); subplot(311); plot(f,fftshift(abs(rf))); xlabel('f');title('加燥2FSK信号频谱'); axis([-fc-2*B,fc+2*B,min(rf),max(rf)+10]); %% 在接收端准备进行解调，先通过带通滤波器 %% 带通滤波器 %生成上下支路两路两个滤波器 %低频载频 [H_low,f_low] = bp_f(length(r),f_start-0.76*B,f_start+0.76*B,df1,fs,1); subplot(323); plot(f_low,fftshift(abs(H_low))); %画出带通滤波器 xlabel('f');title('下支路理想BPF'); axis([-4,4,min(H_low)-0.2,max(H_low)+0.2]); %高频载频 [H_high,f_high] = bp_f(length(r),f_cutoff-0.76*B,f_cutoff+0.76*B,df1,fs,1); subplot(324); plot(f_high,fftshift(abs(H_high))); %画出带通滤波器 xlabel('f');title('上支路理想BPF'); axis([-4,4,min(H_high)-0.2,max(H_high)+0.2]); subplot(325); rf_lowf = H_low .* rf; [rf_low] = F2T_new(rf_lowf,fs); %滤波器输出信号的波形 plot(t,rf_low(1:Lt)); axis([min(t),30,min(rf_low)-0.1,max(rf_low)+0.1]); title('下支路信号'); subplot(326); rf_highf = H_high .* rf; [rf_high] = F2T_new(rf_highf,fs); %滤波器输出信号的波形 plot(t,rf_high(1:Lt)); axis([min(t),20,min(rf_high)-0.1,max(rf_high)+0.1]); title('上支路信号'); %%--------------和本地载波相乘，即混频 %下支路混频信号 figure(4); subplot(421); f_low = 1; f_high = 3; wave_low = A * cos(2*pi*f_low*t); plot(t,wave_low(1:Lt)); axis([min(t),10,min(wave_low)-0.2,max(wave_low)+0.2]); xlabel('t');title('下支路载波'); subplot(423); %频谱载波 [wave_lowf,wave_low,df1,f] = T2F_new(wave_low,ts,df,fs); plot(f,fftshift(abs(wave_lowf)/5)); %画出载波频谱 xlabel('f');title('下支路载波频谱'); axis([-fc-2*B,fc+2*B,0,6]); %再画出混频后信号及其频谱 der_low = rf_low(1:Lt).*wave_low(1:Lt); %混频 subplot(425); %画出混频后的信号 plot(t,der_low); axis([min(t),30,min(der_low)-0.2,max(der_low)+0.2]); xlabel('t');title('混频后的信号'); subplot(427); [der_lowf,der_low,df1,f] = T2F_new(der_low,ts,df,fs); %求出混频后的信号频谱 plot(f,10*log10(abs(fftshift(der_lowf).^2/length(f)))); %画出混频后的信号频谱 xlabel('f');title('混频后的信号功率谱密度'); axis([-fc-6*B,fc+6*B,-50,0]); %% 上支路混频信号 subplot(422); wave_high = A * cos(2*pi*f_high*t); plot(t,wave_high(1:Lt)); axis([min(t),10,min(wave_high)-0.2,max(wave_high)+0.2]); xlabel('t');title('上支路载波'); subplot(424); %频谱载波 [wave_highf,wave_high,df1,f] = T2F_new(wave_high,ts,df,fs); plot(f,fftshift(abs(wave_highf)/5)); %画出功率谱密度 xlabel('f');title('上支路载波频谱'); axis([-fc-3*B,fc+3*B,0,6]); %再画出混频后信号及其频谱 der_high = rf_high(1:Lt).*wave_high(1:Lt); %混频 subplot(426); %画出混频后的信号 plot(t,der_high); axis([min(t),30,min(der_high)-0.2,max(der_high)+0.2]); xlabel('t');title('混频后的信号'); subplot(428); [der_highf,der_high,df1,f] = T2F_new(der_high,ts,df,fs); %求出混频后的信号频谱 plot(f,10*log10(abs(fftshift(der_highf).^2/length(f)))); %画出混频后的信号功率谱密度 xlabel('f');title('混频后信号功率谱密度'); axis([-fc-6*B,fc+6*B,-50,0]); %% 低通滤波器 %-----------------经过低通滤波器 %画出理想低通滤波器 figure(5); [LPF_low,f_low] = lp_f(length(der_high),B,df1,fs,1); %求出低通滤波器 subplot(321); plot(f_low,fftshift(abs(LPF_low))); %画出理想低通滤波器 xlabel('f');title('理想LPF(下支路)'); axis([-f_start-1.5,f_start+1.5,min(LPF_low)-0.1,max(LPF_low)+0.1]); [LPF_high,f_high] = lp_f(length(der_low),B,df1,fs,1); %求出低通滤波器 subplot(322); plot(f_high,fftshift(abs(LPF_high))); %画出理想低通滤波器 xlabel('f');title('理想LPF(上支路)'); axis([-f_start-1.5,f_start+1.5,min(LPF_high)-0.1,max(LPF_high)+0.1]); %% 经过理想低通滤波器后的信号 %混频信号经过理想低通滤波器后的频谱及波形 DM_lowf = LPF_low .* der_lowf; %理想低通滤波器输出的频谱 [dm_low] = F2T_new(DM_lowf,fs); %滤波器的输出波形 DM_highf = LPF_high .* der_highf; [dm_high] = F2T_new(DM_highf,fs); subplot(323); plot(t,dm_low(1:Lt)); axis([min(t),30,min(dm_low)-0.2,max(dm_low)+0.1]); xlabel('t');title('通过理想LPF后的信号(下支路)'); subplot(324); plot(t,dm_high(1:Lt)); axis([min(t),30,min(dm_high)-0.2,max(dm_high)+0.1]); xlabel('t');title('通过理想LPF后的信号(上支路)'); subplot(325); [dm_lowf,dm_low,df1,f] = T2F_new(dm_low,ts,df,fs); %求出混频后的信号频谱 plot(f,10*log10(abs(fftshift(dm_lowf).^2/length(f)))); %画出混频后的信号功率谱密度 xlabel('f');title('信号功率谱密度(下支路)'); axis([-fc-3*B,fc+3*B,-50,0]); subplot(326); [dm_highf,dm_high,df1,f] = T2F_new(dm_high,ts,df,fs); %求出混频后的信号频谱 plot(f,10*log10(abs(fftshift(dm_highf).^2/length(f)))); %画出混频后的信号功率谱密度 xlabel('f');title('信号功率谱密度(上支路)'); axis([-fc-3*B,fc+3*B,-50,0]); figure(6); subplot(311); plot(t,dm_low(1:Lt),'k-.');hold on; plot(t,dm_high(1:Lt),'g-'); axis([min(t),20,min(dm_high)-0.2,max(dm_high)+0.2]); xlabel('t');title('上下支路信号比较'); legend('下支路信号','上支路信号'); set(gca,'XTick',0:1:20); set(gca,'XGrid','on'); panjue = zeros(1,N);%建立存储判决值的矩阵 for i = 1 : Lt if dm_high(i) > dm_low(i) panjue(i) = 1; else panjue(i) = 0; end end subplot(312); plot(t,panjue(1:Lt)); axis([min(t),20,min(panjue)-0.2,max(panjue)+0.2]); xlabel('t');title('恢复信号'); set(gca,'XTick',0:1:20); set(gca,