m基于MATLAB的通信系统仿真,包括信号源,载波信号,放大器,带宽滤波器,接收端包括放大器,带宽滤波器,载波解调,低通滤波器等

1.算法概述

Interference : 200KHz

 

Signal source: 需要在给出的一个excel 文档里调用，我对应的信号是第二竖栏，就是从B1到B60

 

里面所有的filter(滤波器)都是自己来选值，但必须和图里要求的一样，band-pass filter 只能用带通滤波器，不可用其他代替。Low-pass filter(低通滤波器)是同样的道理。

 

Scaling factor为-20，

 

Noise为随机向量*0.3，

 

Interference为200khz。

 

 这个部分主要分为放大器，带宽滤波器，载波解调,原始的信号。

 

2.仿真效果预览

matlab2022a仿真

3.MATLAB部分代码预览 `.................................................

%STEP1 发送端

%信号源

SINGNALS=xlsread('Signals.xls','Sheet1','B1:B600');

figure(1)

subplot(511),plot(SINGNALS),title('原始的信号');

 

%乘以载波

N = 20                       % Set the number of signal samples

Freq = 250000;                 % 250k

dt = 1/(N*Freq);               % Set the sample time

SimTime = 600/Freq;              % Set simulation time to 3 periods of the signal

t = dt:dt:SimTime;              % Create Time vector(from 0 upto SimTime)

Carrier= sin(2piFreq*t);  

subplot(512),plot(Carrier),title('调制载波');

 

%信号采样化

for i = 1 : length(Carrier)-1

SINGNALS1(i) = SINGNALS(floor(i/20)+1);

end

SINGNALS1(length(Carrier)) = SINGNALS1(length(Carrier)-1);

 

SINGNALS2=SINGNALS1.*Carrier;

% SINGNALS2=SINGNALS1.*Carrier + SINGNALS1.*Carrier.*Carrier;

subplot(513),plot(SINGNALS2),title('信号调制信号');

 

%放大

SINGNALS3=15*SINGNALS2;

subplot(514),plot(SINGNALS3),title('模拟放大信号');

 

%带通滤波器

order = 4;

wn = [0.01 0.1];

[B,A]=butter(order,wn);

SINGNALS4 = filter(B,A,SINGNALS3);

subplot(515);plot(SINGNALS4),title('带通滤波后的信号');

 

 

 

%STEP2 信道

figure(2)

 

alpha = -20;                               % scaling factor

noise = 0.3*randn(1,length(SINGNALS4));    % Generate a random number

subplot(211);plot(noise);

 

N2 = N;                                    

Fre = 200000;                              % Set the frequency of the signal

dt2 = 1/(N2*Fre);                          % Set the sample time

SimTime2 = 600/Fre;                        % Set simulation time to 3 periods of the signal

t2 = dt2:dt2:SimTime2;                     % Create Time vector(from 0 upto SimTime

 

interference = sin(2piFre*t2);           % Determine the sinusoidal function for interference

output_sig   = SINGNALS4.* alpha;

 

SINGNALS5 = output_sig + noise + interference;

 

subplot(212);plot(SINGNALS5);

 

%STEP3 接收端

figure(3);

a2=6;

SINGNALS6 = a2*SINGNALS5;

order2 = 4;

wn2 = [0.01 0.1];

[B2,A2]=butter(order2,wn2);

SINGNALS7 = filter(B2,A2,SINGNALS6);

subplot(311);plot(SINGNALS7),title('接收端后的低通滤波信号');

SINGNALS8=-SINGNALS7.*Carrier;  

% SINGNALS8= SINGNALS7.*Carrier;

subplot(312);plot(SINGNALS8),title('解调信号');

wn1 = 0.1;

order1 = 10; % Filter Order

[C,D] = butter(order1,wn1,'low'); % create the fourth order butterworth filter

SINGNALS9 = filter(C,D,SINGNALS8);

subplot(313);plot(SINGNALS9),title('还原后的信号');

figure(4)

subplot(211);plot(SINGNALS);title('系统发送接收信号的对比');

subplot(212);plot(SINGNALS9);axis([0,length(Carrier),0,5000]);

01-29m`