%
% FUNCTION 8.12 : "cp0803_PPMcorrmask_R"
%
% Evaluates the correlation mask ('mask') for a RAKE
% receiver in the case of binary PPM UWB signals.
% 'ref' is the reference signal (with no modulation)
%       which is produced by the 2PPM+TH transmitter
% 'fc' is the sampling frequency in Hertz
% 'numpulses' is the number of transmitted pulses
% 'dPPM' is the value of the PPM shift in seconds
% 'rake' represents the estimated discrete-type impulse
%       response
%
% Programmed by Guerino Giancola
%

function [mask] = ...
   cp0803_PPMcorrmask_R(ref,fc,numpulses,dPPM,rake)

% ---------------------------------------------
% Step One - Evaluation of the correlation mask
% ---------------------------------------------

dt = 1 / fc;
LR = length(ref);

% Energy normalization
Epulse = (sum((ref.^2).*dt))/numpulses;
nref = ref./sqrt(Epulse);

% Rake convolution

mref = conv(nref,rake);
mref = mref(1:LR);

% Mask construction
PPMsamples = floor (dPPM ./ dt);
sref(1:PPMsamples)=mref(LR-PPMsamples+1:LR);
sref(PPMsamples+1:LR)=mref(1:LR-PPMsamples);
mask = mref-sref;