%*************************************************************
% Function to generate ramp
% Input : time interval, signal advance/delay factor
% Output: Ramp response
%**************************************************************
function y = ramp(t,ad)
  % generation of unit step
  % t: time
  % ad : advance (positive), delay (negative)
  N= length(t);
  y = zeros(1,N);
  for i = 1:N,
    if t(i) >= -ad,
      y(i) = t(i);
    end
  end
end