900字范文 > 【数字信号调制】基于matlab二进制数字频率调制（2FSK）【含Matlab源码 998期】

【数字信号调制】基于matlab二进制数字频率调制（2FSK）【含Matlab源码 998期】

时间：2023-02-25 19:27:31

一、获取代码方式

获取代码方式1：

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二、FSK简介

** FSK信号的解调原理**

FSK信号的解调也有非相干和相干两种，FSK信号可以看作是用两个频率源交替传输得到的，所以FSK的接收机由两个并联的ASK接收机组成。

(1)相干解调

相干解调是利用乘法器，输入一路与载频相干的参考信号与载频相乘，通过低通滤波，滤除高频信号，即得原始信号，FSK经过带通滤波之后，可以看作是两路ASK信号，相干检测器组成的原理如下所示：

三、部分源代码

clear allclose alli=10;%基带信号码元数j=5000;a=round(rand(1,i));%产生随机序列t=linspace(0,5,j);f1=10;%载波1频率f2=5;%载波2频率fm=i/5;%基带信号频率%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%产生基带信号st1=t;for n=1:10if a(n)<1;for m=j/i*(n-1)+1:j/i*nst1(m)=0;endelsefor m=j/i*(n-1)+1:j/i*nst1(m)=1;endendendst2=t;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%基带信号求反for n=1:j;if st1(n)>=1;st2(n)=0;elsest2(n)=1;endend;figure(1);subplot(511);plot(t,st1);title('基带信号');axis([0,5,-1,2]);%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%载波信号s1=cos(2*pi*f1*t)s2=cos(2*pi*f2*t)subplot(512),plot(s1);title('载波信号1');subplot(513),plot(s2);title('载波信号2');%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%调制F1=st1.*s1;%加入载波1F2=st2.*s2;%加入载波2fsk=F1+F2;subplot(514);plot(t,fsk);title('2FSK信号')%键控法产生的信号在相邻码元之间相位不一定连续%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%相干解调st1=fsk.*s1;%与载波1相乘[f,sf1] = T2F(t,st1);%通过低通滤波器[t,st1] = lpf(f,sf1,2*fm);st2=fsk.*s2;%与载波2相乘[f,sf2] = T2F(t,st2);%通过低通滤波器[t,st2] = lpf(f,sf2,2*fm);%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%抽样判决%脚本文件F2T.m定义了函数F2T，计算信号的反傅立叶变换。function [t,st]=F2T(f,sf)%This function calculate the time signal using ifft function for the input%signal's spectrumdf = f(2)-f(1);Fmx = ( f(end)-f(1) +df);dt = 1/Fmx;N = length(sf);T = dt*N;%t=-T/2:dt:T/2-dt;t = 0:dt:T-dt;sff = fftshift(sf);st = Fmx*ifft(sff);function [t,st]=lpf(f,sf,B)%This function filter an input data using a lowpass filter%Inputs: f: frequency samples% sf: input data spectrum samples% B: lowpass's bandwidth with a rectangle lowpass%Outputs: t: time samples% st: output data's time samplesdf = f(2)-f(1);T = 1/df;hf = zeros(1,length(f));%全零矩阵bf = [-floor( B/df ): floor( B/df )] + floor( length(f)/2 );hf(bf)=1;yf=hf.*sf;[t,st]=F2T(f,yf);st = real(st);