软件无线电实验matlab程序

附录

(1) 、SDR 低通采样理论

%parameters

fs = 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

%signals

sn = 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);

%figures

figure(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

%parameters

f = 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

%parameters

fs = 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);

%signals

s1

A*cos(2*pi*fc*t).*cos(mf*sin(2*pi*fm*t)); s2

fs 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);

%figures

figure(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%parameters

clear 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

%signals

s = (1+ma*m).*x;% 幅度调制信号

s1= m.*x;% 双边带信号DSB

s2 = 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]);