%
% hrollfcoef.m
%
% Generate coefficients of Nyquist filter
%
%programmed by Huangyong
%

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

%************************* Variables ***********************************

% irfn     :  Number of symbols to use filtering
% ipoint   :  Number of samples in one symbol
% sr       :  symbol rate
% alfs     :  rolloff coefficients
% ncc      :  1__transmitting filter 0__receiving filter

%***********************************************************************

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;            % 4*alpha*R_s

for i=1:n
    icon=i-mid;
    ym=icon;
    
    if icon == 0.0
        xt=(1.0-alfs+4.0.*alfs./pi).*tr;        %h(0)
    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;                                              %h(t)
        else           % (4alphaRst)^2=1
            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   % if sub2 ~=1.0
    end       % if icon ==0.0
    
    if ncc == 0             % in the case of receiver
        xh(i) = xt./ipoint./tr;   % normalization
    elseif ncc == 1         % in the case of transmitter
        xh(i) = xt./tr;
    else
        error('ncc error');
    end                     % if ncc == 0
end                         % for i = 1:n

%************************** end of file ***********************************