www.pudn.com > tryGUI.rar > uwb_sv_cnvrt_ct.m

function [hN,N] = uwb_sv_cnvrt_ct( h_ct, t, np, num_channels, ts ) 
% convert continuous-time channel model h_ct to N-times oversampled discrete-time samples 
% h_ct, t, np, and num_channels are as specified in uwb_sv_model 
% ts is the desired time resolution 
%  
% hN will be produced with time resolution ts / N. 
% It is up to the user to then apply any filtering and/or complex downconversion and then 
% decimate by N to finally obtain an impulse response at time resolution ts. 
 
min_Nfs = 100; % GHz 
N = max( 1, ceil(min_Nfs*ts) );  % N*fs = N/ts is the intermediate sampling frequency before decimation 
N = 2^nextpow2(N); % make N a power of 2 to facilitate efficient multi-stage decimation 
% NOTE: if we force N = 1 and ts = 0.167, the resulting channel hN will be identical to 
% the results from earlier versions that did not use continuous-time. 
Nfs = N / ts; 
t_max = max(t(:));  % maximum time value across all channels 
h_len = 1 + floor(t_max * Nfs);  % number of time samples at resolution ts / N 
hN = zeros(h_len,num_channels); 
for k = 1:num_channels 
  np_k = np(k);  % number of paths in this channel 
  t_Nfs = 1 + floor(t(1:np_k,k) * Nfs);  % vector of quantized time indices for this channel 
  for n = 1:np_k 
    hN(t_Nfs(n),k) = hN(t_Nfs(n),k) + h_ct(n,k); 
  end 
end