%子程序
function [x,bits] =random_binary(nbits,nsamples)
%this function generates a random binary waveform of length nbits
%sampled at a rate of nsamples/bit
x=zeros(1,nbits*nsamples);
bits=round(rand(1,nbits));
for m=1:nbits
    for n=1:nsamples
        index=(m-1)*nsamples+n;
        x(1,index)=(-1)^bits(m);
    end
end