vsbpf.m

北邮《通信原理基于Matlab的计算机仿真》书的源码 m文件 好不容易弄来的

function [t,st]=vsbpf(f,sf,B1,B2,fc)
%This function filter an input by an residual bandpass filter
%Inputs:
%     f:  frequency samples
%     sf: input data spectrum samples
%     B1: residual bandwidth
%     B2: highest freq of the basedband signal 
%Outputs:
%     t: frequency samples
%     st: output data's time samples
df = f(2)-f(1);
T = 1/df;
hf = zeros(1,length(f));

bf1 = [floor( (fc-B1)/df ): floor( (fc+B1)/df )] ;
bf2 = [floor( (fc+B1)/df )+1: floor( (fc+B2)/df )];

f1 = bf1 + floor( length(f)/2 ) ;
f2 = bf2 + floor( length(f)/2 ) ;
stepf = 1/length(f1);
hf(f1)=0:stepf:1-stepf;
hf(f2)=1;

f3 = -bf1 + floor( length(f)/2 ) ;
f4 = -bf2 + floor( length(f)/2) ;
hf(f3)=0:stepf:(1-stepf);
hf(f4)=1;

yf=hf.*sf;
[t,st]=F2T(f,yf);
st = real(st);