% [h] =fir_rrc(fa,Tsym,Alpha,N)
function [b,k,delay] =fir_rrc(fa,Tsym,Alpha,N)

if rem(N,2),
   delay = (N-1)/2;
else
   delay = N/2;
end

n = ((0:N-1)-delay)/fa;

ind1 = find(n == 0);
if ~isempty(ind1),
	b(ind1) = - sqrt(2./Tsym) ./ (pi.*fa) .* (pi.*(Alpha-1) - 4.*Alpha );
end

ind2 = find(abs(abs(8.*Alpha.*n./Tsym) - 1.0) < sqrt(eps));
if ~isempty(ind2),
	b(ind2) = sqrt(2./Tsym) ./ (2.*pi.*fa) ...
		* (    pi.*(Alpha+1)  .* sin(pi.*(Alpha+1)./(4.*Alpha)) ...
		- 4.*Alpha     .* sin(pi.*(Alpha-1)./(4.*Alpha)) ...
		+ pi.*(Alpha-1)  .* cos(pi.*(Alpha-1)./(4.*Alpha)) ...
		);
end

ind = 1:length(n);
ind([ind1 ind2]) = [];
nind = n(ind);

b(ind) = -4.*Alpha./fa .* ( cos((1+Alpha).*2.*pi.*nind./Tsym) + ...
	sin((1-Alpha).*2.*pi.*nind./Tsym) ./ (8.*Alpha.*nind./Tsym) ) ...
	./ (pi .* sqrt(1./(2./Tsym)) .* ((8.*Alpha.*nind./Tsym).^2 - 1));

b = sqrt(2./Tsym) .* b;
k=0.5*fa*Tsym;