lpf.m

使用matlab程序实现了由随机序列到码元电平、m序列直接扩频解扩、qpsk调制解调

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 samples

df= f(2)-f(1);
T=1/df;
hf=zeros(1,length(f));
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);