% hrollfcoef.m
%
%  Generate coefficients of Nyquist filter

function [xh]=hrollfcoef(irfn,ipoint,sr,alfs,ncc)

xi=zeros(1,irfn*ipoint+1);
xq=zeros(1,irfn*ipoint+1);
point=ipoint;
tr=sr;
tstp=1.0./tr./ipoint;
n=ipoint.*irfn;
mid=(n./2)+1;
sub1=4.0.*alfs.*tr;

for i=1:n
    icon=i-mid;
    ym=icon;
    if icon==0.0
        xt=(1.0-alfs+4.0.*alfs./pi).*tr;
    else
        sub2=16.0.*alfs.*alfs.*ym.*ym./ipoint./ipoint;
        if sub2~=1.0
            x1=sin(pi*(1.0-alfs)/ipoint*ym)./pi./...
                (1.0-sub2)./ym./tstp;
            x2=cos(pi*(1.0+alfs)/ipoint*ym)./pi.*sub1./(1.0-sub2);
            xt=x1+x2;
        else
            xt=alfs.*tr.*((1.0-2.0/pi).*cos(pi/4.0/alfs)+(1.0+2.0./pi).*...
                sin(pi/4.0/alfs))./sqrt(2.0);
        end
    end
    if ncc==0
        xh(i)=xt./ipoint./tr;
    elseif ncc==1
        xh(i)=xt./tr;
    else
        error('ncc error');
    end
end