附录(1) 、SDR 低通采样理论%parametersfs = 5e4;%采样频率注意或 2 倍以上f = 5e3;%信号的频率N = 1024;n = 1:1024;t= n/fs;deta_t = 1/fs;% 采样间隔%signalssn = sin(2*pi*f*t);% 时域采样后的信号w = hanning(N);% 加汉宁窗sn1 = sn.*w';% 加窗减少频率泄露Sn_fft = fft(sn1);% 频域信号Sn = abs(Sn_fft);%figuresfigure(1);plot(t,sn);title('s(n)的时域波形');grid on;xlabel('t');xlim([0 0.021]);ylabel('幅度');figure(2);xax = [-N/2:N/2-1]/N*fs/1000;% 将f 轴单位变为kHz plot(xax,20*log10(fftshift(Sn))); title('s(n)的频域波形');grid on;xlabel('f(kHz)'); ylabel('幅度(dB)');ylim([-200 100]);(2) 、SDR 带通采样理论%parametersf = 1.3e3;% 基频fo = 100e6;% 载波频率N = 1024;fs = 4e3;%采样频率t= 0:0.001:2; st = cos(2*pi*(f+fo)*n/fs);% 带通抽样信号St1 = fft(st);St = abs(St1);st0 = cos(2*pi*(f+fo)*t);St0 = fft(st0);St2 = abs(St0);figure(1);plot(n,st);title('带通抽样信号时域图像’)；xlabel('n');xlim([0 1026]);ylabel('幅度');grid on;figure(2);plot(t,st0);title('带通原始信号时域图像');xlabel('t');ylabel('幅度');grid on;figure(3);xax =[-N/2:N/2-1]/N*fs/1000;plot(xax,20*log10(fftshift(St)));title('带通信号抽样后频域图像’)；xlabel('f(kHz)');ylabel('幅度(dB)');grid on;(3) 、频率调制信号%频率调制%parametersfs = 1e3;%抽样频率ts = 1/fs;%采样率N = 1024;n = 0:1:N-1;t = n/fs;kf = 100.1;A = 100;Aw = 10;fc = 10000;% 载波频率fm = 10;% 调制信号频率mf = kf*Aw/(2*pi*fm);%signalss1A*cos(2*pi*fc*t).*cos(mf*sin(2*pi*fm*t)); s2fs 至少是f 的2 倍n = 1:1024;A*sin(2*pi*fc*t).*sin(mf*sin(2*pi*fm*t)); s = s1-s2;% 频率调制信号S0 = fft(s);S1 = fftshift(S0);S_0 = abs(S1);%figuresfigure(1);plot(t,s);title(' 频率调制信号时域图像');xlim([0,0.5]);xlabel('t(s)');ylabel('幅度');grid on;figure(2);xax = [-N/2:N/2-1]/N*fs/1000;plot(xax,20*log10(S_0));title(' 频率调制信号频域图像');xlabel('f(kHz)');ylabel('幅度(dB)');grid on;(4) 、幅度调制信号、DSB 信号、USB 信号%parametersclear all;clc;close all;fs = 1e3;%抽样频率ts = 1 /fs ;%采样间隔N = 10000;n = 1:N;t = n/fs;ma = 0.5;fc = 200;%载波频率x = cos(2*pi*fc*t);% 生成载波fm = 1 ;%调制信号频率m = cos(2*pi*fm*t);% 基带信号%signalss = (1+ma*m).*x;% 幅度调制信号s1= m.*x;% 双边带信号DSBs2 = cos(2*pi*(fc+fm)*t);%SSB 信号中的USB S1 = fft(s);S_1 = abs(S1);S2 = fft(s1); S_2 = abs(S2);S3 = fft(s2);S_3 = abs(S3);%figures figure(1); plot(t,s);title('幅度调制信号时域图像'); xlim([0 1.5]);xlabel('t(s)');ylabel('幅度');grid on;figure(2);xax = [-N/2:N/2-1]/N*fs/1000; plot(xax,20*log10(fftshift(S_1))); title('幅度调制信号频域图像'); xlim([0.19 0.21]);xlabel('f(kHz)');ylabel('幅度(dB)');grid on;figure(3);plot(t,s1);title('双边带调制信号时域图像'); xlim([0 1.5]);xlabel('t(s)');ylabel('幅度');grid on;figure(4);xax1 = [-N/2:N/2-1]/N*fs/1000; plot(xax1,20*log10(fftshift(S_2))); title(' 双边带调制信号频域图像'); xlim([0.19 0.21]);xlabel('f(kHz)');ylabel('幅度(dB)');grid on;figure(5);plot(t,s2);title('USB 调制信号时域图像'); xlim([0 1.0]);xlabel('t(s)'); ylabel('幅度');grid on;figure(6);xax1 = [-N/2:N/2-1]/N*fs/1000;plot(xax1,20*log10(fftshift(S_3))); title('USB 调制信号频域图像'); xlim([0.19 0.21]);xlabel('f(kHz)'); ylabel('幅度(dB)');grid on;(5) 、2ASK 信号%2ASK 信号的时域和频域分析clear all;clc;close all;% 清除一切。

m = [1 1 1 0 0 0 1 0 1 1 0 1];% 数字信号的序列(自己随便产生的)Lm = length(m);% 序列的长度F = 200 ;%数字信号的带宽('1'或'0'的带宽是200Hz)f = 800;% 正弦载波信号的频率A = 1;% 载波的幅度Q = f/F;%频率比，即一个码元宽度中的正弦周期个数%signalscarry1 = repmat(A*sin(2*pi*f*t),1,Q);% 一个码元宽度内的正弦载波信号Lcarry1 = length(carry1);% 一个码元宽度内的信号长度carry2 = kron(ones(size(m)),carry1);% 载波信号ask = kron(m,carry1);% 调制后的ASK 信号N = length(ask);%ASK 信号的长度tau = (0:N-1)/(M-1)/f;% 时间Tmin = min(tau);% 最小时间Tmax = max(tau);% 最大时间T = on es(size(carry1));% —个数字信号’1' dsig = kron(m,T);Ask = fft(ask); Ask0 = abs(Ask);%imagesfigure(1);plot(tau,dsig);grid on;axis([Tmin Tmax -0.2 1.2]); title('数字信号序列的图像');figure(2); plot(tau,carry2);xlim([0 0.06]);grid on;title('载波时域图像');figure(3);plot(tau,ask);grid on;axis([Tmin Tmax -1.2*A 1.2*A]); title('2ASK 信号的时域图像');M = 500;% 一个正弦周期内的采样点数t = (0:M-1)/M/f;% 一个正弦信号周期内的时间figure(4);xax = [-N/2:N/2-1]/N*Lm*F;plot(xax,20*log10(fftshift(Ask0)));xlim([-300 300]);title('2ASK 信号的频域图像');grid on;(6) 、16 路信道化发射机%parameters clc;close all;clear all;a = 1;% 幅度fs = 50;% 内插前采样频率k = 1:16;%16 路信号I = 16;% 内插系数N = 1024;fk = 1:1:N;sk = zeros(16,N);% 创建16 行N 列的零矩阵用来存放16 路时域信号Sk = zeros(16,N);% 创建16 行N 列的零矩阵用来存放16 路频域信号for k = 1:16sk(k,:) = a*(1+0.5*exp(j*2*pi*k*fk/fs));% 输入16 路时域信号endfor k = 1:16Sk(k,:) = fft(sk(k,:));%16 路信号频域endfigure(1);xax = [-N/2:N/2-1]/N*fs;plot(xax,20*log10(abs(fftshift(Sk(:,1:N))))); title('16 原始复信号时域叠加图');xlabel('f(Hz)');xlim([-5 25]);ylabel('幅度');figure(2);h0 = fir1(265,0.5);HW = fft(h0,N);xax1 = [-N/2:N/2-1]/N*fs;plot(xax1,10*log10(abs(fftshift(HW)))); title(' 滤波器响应');xlabel('f(Hz)'); ylabel('幅度');%I 倍内插，即16 倍内插，此时fs 变大N_1 = N*16;st = zeros(16,N_1);St = zeros(16,N_1);for k = 1:16for g = 0:N-1st(k,g*I+k) = sk(k,g+1);endendsum = zeros(1,N_1);for k = 1:16sum = sum+st(k,1:N_1);endfor k = 1:16St(k,:) = fft(sum(1,1:N_1)); endfor k = 1:16St(k,1:N) = St(k,1:N).*HW; endfigure(3);xax3 = [-N_1/2:N_1/2-1]/N_1*fs*16;plot(xax3,sum(1,:));title('内插后信号时域图像’)；xlim([-60 60]);xlabel('t')； ylabel('幅度');figure(4)；xax2 = [-N/2:N/2-1]/N*fs*16;plot(xax2,db(abs(fftshift(St(:,1:N)))));title('内插后信号频域图像’)；xlim([-10 200]);xlabel('f(Hz)'); ylabel('幅度');。