function g = er_upsample(f,N)
% function g = er_upsample(f,N)
%   Function to upsample given transfer function in struct F by factor of N.
%
%   Author:  Evan Ruzanski, CU-Boulder, ECEN5632 MATLAB assignment, FA2004

% Unpack
num1 = f(1).tf_complete;
den1 = f(2).tf_complete;
% Modulate
L1 = length(num1);
num2 = zeros(1,2*L1-1);
num2(1:N:length(num2)) = num1;
L2 = length(den1);
den2 = zeros(1,2*L2-1);
den2(1:N:length(den2)) = den1;
% Repack
f(1).tf_complete = num2;
f(2).tf_complete = den2;
g = f;