<matlab> Hadamard矩陣實現CDMA信道walsh正交碼
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%  該函數通過輸入因子生成相應階數的哈達曼(Hadamard)矩陣    %
%  利用哈達曼矩陣得到正交的walsh矩陣，參數num為矩陣階數    %
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function [walsh_matrix] = walsh_sequence_generator(num)
if nargin < 1                                      % 如果輸入參數為空，默認輸出0階哈達曼矩陣
    num = 0;
end
if rem(log2(num),1) ~= 0 | num < 0 | num == 1
    error('參數 num 必須是非負的正整數,且必須為2的冪次 !');
end
walsh_matrix = [];                             % 初始化輸出walsh序列矩陣
if num == 0
    walsh_matrix = [1];                       % 參數為零的Hadamard矩陣
elseif num == 2
    walsh_matrix = [1 1;1 -1];              % 參數為2的2階Hadamard矩陣
else
    walsh_matrix = [1 1;1 -1];
    for k = 1:log2(num)-1                    % 循環生成log2(num)階Hadamard矩陣
        walsh_matrix = [walsh_matrix,walsh_matrix;walsh_matrix,-walsh_matrix]; 
    end    
end