get_preamble_signal.m

一个UWB仿真程序包

% Return preamble_signal: upsampled, pulse shaped and channel filtered version of
% tx_signal,
%
% ch_len: length of channel impulse response in samples
% tx_signal: the transmitted signal
% TC: length of a chip in ns
% FS_CONT: sampling frequency of "continuous" signal
% CH_MODEL: number of channel model to use
% CH_ATT_THLD_DB: rays with bigger attenuation are considered 0 in channel
% impulse response
% CH_RNG_SEED: seed of rng when drawing channel
% PLOT_DEBUG: flag to indicate whether to make plots or not
%
% function [rx] = get_preamble_signal(tx_signal,...
%    compound_channel, ch_len, chip_span, TC,FS_CONT,PLOT_DEBUG)

function [rx] = get_preamble_signal(tx_signal,...
    compound_channel, ch_len, chip_span, TC,FS_CONT,PLOT_DEBUG)

samples_per_chip = TC * FS_CONT;

%upsample to match FS_CONT
tx_signal_up = upsample(tx_signal,samples_per_chip);


rx = zeros(1,ch_len + length(tx_signal_up) - 1);

%as most of the entries in tx_signal_up are zero, we can perform a
%faster algo than convolution by just replicating the whole compound
%channel at positions where we have +1 (-1) in the tx_signal_up signal.
non_null_ind = find(tx_signal_up ~= 0);
for i=1:length(non_null_ind)
    rx(non_null_ind(i):non_null_ind(i)+ch_len-1) = ...
        rx(non_null_ind(i):non_null_ind(i)+ch_len-1) + tx_signal_up(non_null_ind(i)).*compound_channel;
end


%cut overlap from the chip_span, chip_span - 0.5 all-zero chips in beginning
if(chip_span~=0.5)
    rx = ...
        rx((chip_span-0.5)*samples_per_chip+1:end-((chip_span-0.5)*samples_per_chip));
end

return;