function y = my_rrcosflt(x, fd, fs, beta, delay, fsflag)% MY_RRCOSFLT Filter the input signal using a root raised cosine filter.%    Y = MY_RRCOSFLT(X, Fd, Fs, BETA, DELAY) filters the input signal X%    using a root raised cosine FIR filter. The sample frequency for the%    input, X, is Fd (Hz). The sample frequency for the output, Y, is%    Fs (Hz). Fs must be an integer multiple of Fd. The rolloff factor BETA%    determines the width of the transition band of the filter. DELAY is%    the time delay from the beginning of the filter to the peak of the%    impulse response, expressed as the number of input sample periods,%    i.e., the delay in seconds is DELAY/Fd. %%    BETA, the rolloff factor, specifies the excess bandwidth of the%    filter. BETA must be in the range [0,1]. For example, BETA = .5 means%    that the bandwidth of the filter is 1.5 times the input sampling%    frequency, Fd. This also means that the transition band of the filter%    extends from .5 * Fd to 1.5 * Fd. Typical values for BETA are between%    0.2 to 0.5. %%    DELAY determines the length of the filter impulse response used to%    filter X. This length is Fs/Fd * (2 * DELAY) + 1. %%    Y is the output of the upsamled, filtered input stream X. The length%    of the vector Y is%        Fs/Fd * (length(X) + 2 * DELAY).%%    Y = MY_RRCOSFLT(X, Fd, Fs, BETA, DELAY, 'Fs') assumes that the input%    signal X is already at sampling frequency Fs.  %%    The input X can be a row or a column vector, the output Y is always a%    column vector. %santosh shah, The LNM IIT Jaipur (India)(santosh.jnt@gmail.com) 25/04/07% Check argumentsif (fs / fd ~= floor(fs/fd))    error('Fs/Fd must be an integer.');else    upfactor = fs / fd;endif beta < 0 || beta > 1    error('The rolloff factor BETA must be in the range [0,1].');endif (delay < 0) || delay ~= floor(delay)    error('DELAY must be a positive integer.');endif nargin >= 6    if strcmpi(fsflag, 'Fs')        fsflag = true;    else        error('Invalid value for FSFLAG');    endelse    fsflag = false;end% Upsample input signal unless fsflag is setif fsflag    xup = x;else    xup = upsample(x, upfactor);end% Create the filterf = my_rrc(fd, fs, beta, delay);% Filter the input signal and convert to column vectory = conv(xup, f);y = y(:);endfunction 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. 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