function f = my_rrc(fd, fs, beta, delay)% MY_RRC Produces the impulse response of a root raised cosine filter%    F = MY_RRC(Fd, Fs, BETA, DELAY) is the impulse response of a root%    raised cosine FIR filter with rolloff factor BETA and delay DELAY. % $Id: my_rrc.m 457 2006-11-09 08:29:13Z kleiner $BETA = beta;DELAY = delay;FD = fd;FS = fs;% time vectorTd = 1/FD;% Length of actual filter coefficients (rest is zero)rrclen = FS/FD * DELAY * 2 + 1;% Create vector of time instants (make it a column vector to behave as the% MATLAB function rcosflt)t = linspace(-DELAY*Td, DELAY*Td, rrclen)';rrc_num = 4*BETA / (pi*sqrt(Td)) * ...    (cos((1+BETA)*pi*t/Td) + (1-BETA)*pi/(4*BETA) * ...    sinc((1 - BETA)*t/Td));rrc_denom = (1 - (4*BETA * t/Td).^2);rrc = rrc_num ./ rrc_denom;% Determine if there is a singularity (at positions t = +/- 1/(4*BETA))% The value at these points can be obtained by the De l'Hopital rule.ind = find(abs(t) == Td/(4*BETA));if ~isempty(ind)    rrc(ind) = 4*BETA / (pi * sqrt(Td)) * ...        ( (-2 + pi)*cos(pi / (4*BETA)) + ...        (2+pi) * sin(pi / (4*BETA))) / (4*sqrt(2));end% Normalizef = rrc / sqrt(FS);end