ins.m

some simulation on digital FM,as well as some dsp implemention

function [ output_args ] = ins( input_args )
%UNTITLED1 Summary of this function goes here
%   Detailed explanation goes here

% 原始信号
N=128;
fs=1;
f1=0.1;
w=2*pi*f1/fs;
data=sin(w*[0:N-1]);
fx=-0.5:1/N:0.5-1/N;
fx2=-0.5:1/(2*N):0.5-1/(2*N);

% 0 值插值
datainsert(2*N)=0;
k=1;
while k<=N
    datainsert(2*(k-1)+1)=data(k);
    k=k+1;
end

% 低通滤波
b=fir1(64,0.2); % 本来应该是 0.25 的
datafilter=filter(b,1,datainsert);

%显示频域波形
datafft=fftshift(abs(fft(data)));
subplot(6,1,1);
plot(fx,datafft);

datafft=fftshift(abs(fft(datainsert)));
subplot(6,1,2);
plot(fx2,datafft);

datafft=fftshift(abs(fft(datafilter)));
subplot(6,1,3);
plot(fx2,datafft);

%显示时域波形
subplot(6,1,4);
stem(data);
subplot(6,1,5);
stem(datainsert);
subplot(6,1,6);
stem(datafilter);