detection_dsss.m

％ 直接序列扩频信号检测程序 ％ 检测方法：平方倍频法

clear all;

% 直接序列扩频信号检测程序
% 检测方法：平方倍频法

N=1000;
pn=[1	-1	-1	-1	-1	-1	-1	-1	-1	-1	1	-1	-1	1	-1	-1	1	-1	-1	1	1	-1	1	-1	-1	1	1	-1	1	-1	1	1	1	1	1	-1	-1	1	1	-1	-1	-1	1	1	1	1	1	-1	-1	1	-1	-1	-1	1	1	1	-1	1	1	1	1	1	1	-1	-1	-1	-1	1	1	1	-1	-1	-1	-1	-1	-1	-1	1	1	1	1	1	1	1	1	1	1	-1	-1	-1	1	1	1	-1	-1	-1	1	-1	-1	1	1	1	-1	1	1	-1	-1	1	-1	1	-1	1	1	1	-1	1	1	1	1	-1	1	-1	1	-1	-1	-1	1	1	1	1	-1	1	-1	-1	1	-1	1	-1	1	-1	-1	-1	-1	-1	1	-1	1	1	1	1	1	1	1	1	-1	1	-1	1	-1	1	-1	1	-1	1	1	1	1	-1	1	-1	-1	-1	-1	1	1	1	-1	1	-1	-1	1	-1	-1	-1	1	1	-1	-1	1	-1	1	1	-1	1	-1	1	1	-1	-1	1	1	1	1	-1	1	-1	1	1	-1	-1	-1	1	1	-1	-1	1	1	1	1	1	1	-1	-1	1	-1	1	-1	1	-1	1	-1	-1	1	1	-1	-1	1	1	-1	-1	1	-1	1	-1	-1	1	1	1	1	1	-1	1	-1	-1	1	1	1	-1	-1	-1	-1	1	-1	-1	-1	1	1	-1	1	1	-1	-1	1	-1	-1	-1	1	-1	1	-1	-1	1	1	-1	1	1	1	1	-1	1	1	1	-1	1	-1	1	-1	1	1	1	-1	-1	1	1	-1	-1	1	1	1	-1	1	1	1	-1	1	1	1	-1	-1	1	1	1	-1	1	-1	1	-1	-1	1	1	1	-1	1	-1	-1	-1	-1	-1	1	1	1	1	-1	1	1	-1	1	1	1	-1	-1	-1	-1	1	1	-1	-1	-1	1	-1	-1	1	-1	1	-1	-1	1	-1	1	1	-1	-1	1	1	-1	1	-1	-1	-1	1	-1	-1	-1	1	-1	1	1	-1	1	-1	-1	1	-1	1	1	1	-1	1	-1	-1	1	1	-1	-1	-1	1	-1	1	1	-1	-1	-1	-1	-1	-1	1	-1	1	-1	-1	1	-1	-1	1	-1	1	1	1	1	1	-1	1	1	1	1	-1	-1	-1	1	1	-1	-1	-1	1	1	-1	1	1	1	-1	1	1	-1	-1	-1	-1	1	1	1	1	-1	-1	1	-1	-1	1	1	1	-1	-1	1	-1	1	1	-1	-1	-1	1	-1	-1	-1	-1	1	1	-1	1	1	1	1	1	1	1	-1	-1	1	1	1	-1	-1	-1	1	1	-1	1	-1	1	-1	-1	1	-1	1	-1	-1	-1	-1	1	-1	-1	-1	-1	1	-1	-1	1	-1	1	1	-1	1	1	1	1	1	-1	1	-1	1	1	1	-1	-1	-1	1	-1	1	1	1	-1	-1	1	-1	-1	-1	-1	1	1	1	1	1	-1	1	1	-1	1	-1	1	-1	1	-1	-1	-1	1	-1	1	1	1	1	-1	1	1	-1	-1	1	1	1	-1	-1	1	1	1	1	1	-1	-1	-1	-1	-1	1	1	1	-1	-1	1	-1	-1	1	-1	1	-1	1	1	-1	-1	1	-1	1	1	1	1	-1	-1	1	-1	1	1	1	-1	-1	-1	-1	-1	1	-1	1	-1	1	1	-1	1	1	-1	-1	1	1	-1	-1	-1	-1	1	1	-1	1	-1	1	1	-1	1	1	1	-1	1	-1	-1	-1	1	-1	1	-1	1	1	1	1	1	1	-1	1	-1	-1	-1	1	1	1	-1	-1	1	1	-1	1	1	1	-1	-1	1	-1	1	-1	-1	-1	1	1	-1	1	-1	-1	-1	-1	-1	-1	1	1	-1	-1	1	-1	-1	1	-1	-1	-1	1	-1	-1	-1	-1	-1	1	-1	-1	1	1	-1	1	1	-1	1	-1	-1	1	1	1	1	-1	-1	1	1	-1	1	-1	1	-1	1	1	-1	-1	-1	-1	1	-1	1	1	1	-1	1	1	-1	1	-1	-1	-1	1	1	-1	-1	-1	-1	1	-1	-1	1	1	1	1	1	1	1	-1	1	1	1	-1	-1	-1	1	1	1	1	-1	-1	-1	-1	-1	-1	1	1	1	-1	1	1	-1	1	1	-1	-1	-1	1	-1	1	-1	-1	-1	1	-1	-1	1	1	-1	-1	1	-1	-1	-1	-1	-1	1	1	-1	1	-1	-1	1	-1	-1	1	1	1	1	-1	1	1	1	1	1	-1	-1	-1	1	-1	1	-1	1	-1	1	1	-1	1	-1	-1	-1	-1	1	-1	1	-1	-1	-1	-1	-1	-1	-1	1	-1	1	1	-1	1	1	-1	1	1	1	1	-1	-1	1	1	1	1	-1	-1	-1	1	-1	-1	-1	1	1	1	1	1	1	-1	1	1	-1	-1	-1	1	1	1	-1	1	-1	1	1	-1	1	-1	1	-1	-1	-1	-1	1	1	-1	-1	1	1	-1	1	1	-1	-1	-1	-1	-1	1	1	-1	-1	-1	-1	-1	-1	-1	-1	1	1	-1	1	1	-1	1	1	-1	1	-1	1	1	1	-1	1	-1	1	1	1	1	-1	-1	-1	-1	1	-1	1	-1	1	-1	-1	1	-1	-1	-1	-1	1	-1	1	1	-1	-1	1];
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carry_signal=[0	0.58779	0.95106	0.95106	0.58779	1.2246e-016	-0.58779	-0.95106	-0.95106	-0.58779	-2.4493e-016	0.58779	0.95106	0.95106	0.58779	3.6739e-016	-0.58779	-0.95106	-0.95106	-0.58779	-4.8986e-016	0.58779	0.95106	0.95106	0.58779	6.1232e-016	-0.58779	-0.95106	-0.95106	-0.58779	-7.3479e-016	0.58779	0.95106	0.95106	0.58779	8.5725e-016	-0.58779	-0.95106	-0.95106	-0.58779	-9.7972e-016	0.58779	0.95106	0.95106	0.58779	1.1022e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.2246e-015	0.58779	0.95106	0.95106	0.58779	4.8998e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.4696e-015	0.58779	0.95106	0.95106	0.58779	-1.9607e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.7145e-015	0.58779	0.95106	0.95106	0.58779	5.3897e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.9594e-015	0.58779	0.95106	0.95106	0.58779	-1.4708e-015	-0.58779	-0.95106	-0.95106	-0.58779	-2.2044e-015	0.58779	0.95106	0.95106	0.58779	5.8795e-015	-0.58779	-0.95106	-0.95106	-0.58779	-2.4493e-015	0.58779	0.95106	0.95106	0.58779	-9.8096e-016	-0.58779	-0.95106	-0.95106	-0.58779	-9.7997e-015	0.58779	0.95106	0.95106	0.58779	6.3694e-015	-0.58779	-0.95106	-0.95106	-0.58779	-2.9392e-015	0.58779	0.95106	0.95106	0.58779	-4.911e-016	-0.58779	-0.95106	-0.95106	-0.58779	3.9213e-015	0.58779	0.95106	0.95106	0.58779	6.8593e-015	-0.58779	-0.95106	-0.95106	-0.58779	-3.429e-015	0.58779	0.95106	0.95106	0.58779	-1.238e-018	-0.58779	-0.95106	-0.95106	-0.58779	-1.0779e-014	0.58779	0.95106	0.95106	0.58779	7.3491e-015	-0.58779	-0.95106	-0.95106	-0.58779	-3.9189e-015	0.58779	0.95106	0.95106	0.58779	4.8862e-016	-0.58779	-0.95106	-0.95106	-0.58779	2.9416e-015	0.58779	0.95106	0.95106	0.58779	7.839e-015	-0.58779	-0.95106	-0.95106	-0.58779	-4.4087e-015	0.58779	0.95106	0.95106	0.58779	9.7848e-016	-0.58779	-0.95106	-0.95106	-0.58779	-1.1759e-014	0.58779	0.95106	0.95106	0.58779	8.3288e-015	-0.58779	-0.95106	-0.95106	-0.58779	-4.8986e-015	0.58779	0.95106	0.95106	0.58779	1.5679e-014	-0.58779	-0.95106	-0.95106	-0.58779	1.9619e-015	0.58779	0.95106	0.95106	0.58779	8.8187e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.9599e-014	0.58779	0.95106	0.95106	0.58779	1.9582e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.2739e-014	0.58779	0.95106	0.95106	0.58779	-4.9023e-015	-0.58779	-0.95106	-0.95106	-0.58779	-5.8783e-015	0.58779	0.95106	0.95106	0.58779	1.6659e-014	-0.58779	-0.95106	-0.95106	-0.58779	9.8219e-016	0.58779	0.95106	0.95106	0.58779	9.7984e-015	-0.58779	-0.95106	-0.95106	-0.58779	7.8427e-015	0.58779	0.95106	0.95106	0.58779	2.9379e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.3719e-014	0.58779	0.95106	0.95106	0.58779	-3.9226e-015	-0.58779	-0.95106	-0.95106	-0.58779	-6.858e-015	0.58779	0.95106	0.95106	0.58779	1.7639e-014	-0.58779	-0.95106	-0.95106	-0.58779	2.4759e-018	0.58779	0.95106	0.95106	0.58779	1.0778e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.1559e-014	0.58779	0.95106	0.95106	0.58779	3.9176e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.4698e-014	0.58779	0.95106	0.95106	0.58779	-2.9429e-015	-0.58779	-0.95106	-0.95106	-0.58779	-7.8377e-015	0.58779	0.95106	0.95106	0.58779	1.8618e-014	-0.58779	-0.95106	-0.95106	-0.58779	-9.7724e-016	0.58779	0.95106	0.95106	0.58779	1.1758e-014	-0.58779	-0.95106	-0.95106	-0.58779	5.8833e-015	0.58779	0.95106	0.95106	0.58779	4.8973e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.5678e-014	0.58779	0.95106	0.95106	0.58779	-1.9631e-015	-0.58779	-0.95106	-0.95106	-0.58779	-8.8175e-015	0.58779	0.95106	0.95106	0.58779	1.9598e-014	-0.58779	-0.95106	-0.95106	-0.58779	-1.957e-015	0.58779	0.95106	0.95106	0.58779	1.2738e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.3518e-014	0.58779	0.95106	0.95106	0.58779	5.8771e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.6658e-014	0.58779	0.95106	0.95106	0.58779	-9.8343e-016	-0.58779	-0.95106	-0.95106	-0.58779	-9.7972e-015	0.58779	0.95106	0.95106	0.58779	2.0578e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.1358e-014	0.58779	0.95106	0.95106	0.58779	-1.4704e-014	-0.58779	-0.95106	-0.95106	-0.58779	3.9238e-015	0.58779	0.95106	0.95106	0.58779	6.8568e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.7637e-014	0.58779	0.95106	0.95106	0.58779	2.8418e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.9199e-014	0.58779	0.95106	0.95106	0.58779	-6.8642e-015	-0.58779	-0.95106	-0.95106	-0.58779	-3.9164e-015	0.58779	0.95106	0.95106	0.58779	1.4697e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.5478e-014	0.58779	0.95106	0.95106	0.58779	3.6258e-014	-0.58779	-0.95106	-0.95106	-0.58779	9.8046e-015	0.58779	0.95106	0.95106	0.58779	9.76e-016	-0.58779	-0.95106	-0.95106	-0.58779	-1.1757e-014	0.58779	0.95106	0.95106	0.58779	2.2537e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.3318e-014	0.58779	0.95106	0.95106	0.58779	-1.2745e-014	-0.58779	-0.95106	-0.95106	-0.58779	1.9644e-015	0.58779	0.95106	0.95106	0.58779	8.8162e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.9597e-014	0.58779	0.95106	0.95106	0.58779	3.0377e-014	-0.58779	-0.95106	-0.95106	-0.58779	1.5685e-014	0.58779	0.95106	0.95106	0.58779	-4.9048e-015	-0.58779	-0.95106	-0.95106	-0.58779	-5.8758e-015	0.58779	0.95106	0.95106	0.58779	1.6656e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.7437e-014	0.58779	0.95106	0.95106	0.58779	3.8218e-014	-0.58779	-0.95106	-0.95106	-0.58779	7.8452e-015	0.58779	0.95106	0.95106	0.58779	2.9354e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.3716e-014	0.58779	0.95106	0.95106	0.58779	2.4497e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.5277e-014	0.58779	0.95106	0.95106	0.58779	-1.0786e-014	-0.58779	-0.95106	-0.95106	-0.58779	4.9518e-018	0.58779	0.95106	0.95106	0.58779	1.0776e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.1556e-014	0.58779	0.95106	0.95106	0.58779	3.2337e-014	-0.58779	-0.95106	-0.95106	-0.58779	-4.3117e-014	0.58779	0.95106	0.95106	0.58779	-2.9453e-015	-0.58779	-0.95106	-0.95106	-0.58779	-7.8353e-015	0.58779	0.95106	0.95106	0.58779	1.8616e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.9396e-014	0.58779	0.95106	0.95106	0.58779	4.0177e-014	-0.58779	-0.95106	-0.95106	-0.58779	5.8857e-015	0.58779	0.95106	0.95106	0.58779	4.8949e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.5675e-014	0.58779	0.95106	0.95106	0.58779	2.6456e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.7237e-014	0.58779	0.95106	0.95106	0.58779	-8.8261e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.9545e-015	0.58779	0.95106	0.95106	0.58779	1.2735e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.3516e-014	0.58779	0.95106	0.95106	0.58779	3.4296e-014	-0.58779	-0.95106	-0.95106	-0.58779	1.1767e-014	0.58779	0.95106	0.95106	0.58779	-9.8591e-016	-0.58779	-0.95106	-0.95106	-0.58779	-9.7947e-015	0.58779	0.95106	0.95106	0.58779	2.0575e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.1356e-014	0.58779	0.95106	0.95106	0.58779	4.2137e-014	-0.58779	-0.95106	-0.95106	-0.58779	3.9263e-015	0.58779	0.95106	0.95106	0.58779	6.8543e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.7635e-014	0.58779	0.95106	0.95106	0.58779	2.8416e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.9196e-014	0.58779	0.95106	0.95106	0.58779	-6.8667e-015	-0.58779	-0.95106	-0.95106	-0.58779	-3.9139e-015	0.58779	0.95106	0.95106	0.58779	1.4695e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.5475e-014	0.58779	0.95106	0.95106	0.58779	3.6256e-014	-0.58779	-0.95106	-0.95106	-0.58779	-4.7036e-014	0.58779	0.95106	0.95106	0.58779	9.7353e-016	-0.58779	-0.95106	-0.95106	-0.58779	-1.1754e-014	0.58779	0.95106	0.95106	0.58779	2.2535e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.3315e-014	0.58779	0.95106	0.95106	0.58779	4.4096e-014	-0.58779	-0.95106	-0.95106	-0.58779	1.9669e-015	0.58779	0.95106	0.95106	0.58779	8.8137e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.9594e-014	0.58779	0.95106	0.95106	0.58779	3.0375e-014	-0.58779	-0.95106	-0.95106	-0.58779	-4.1156e-014	0.58779	0.95106	0.95106	0.58779	5.1936e-014	-0.58779	-0.95106	-0.95106	-0.58779	-6.2717e-014	0.58779	0.95106	0.95106	0.58779	7.3497e-014	-0.58779	-0.95106	-0.95106	-0.58779	2.9409e-014	0.58779	0.95106	0.95106	0.58779	-1.8628e-014	-0.58779	-0.95106	-0.95106	-0.58779	7.8476e-015	0.58779	0.95106	0.95106	0.58779	2.933e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.3714e-014	0.58779	0.95106	0.95106	0.58779	2.4494e-014	-0.58779	-0.95106	-0.95106	-0.58779	-3.5275e-014	0.58779	0.95106	0.95106	0.58779	4.6055e-014	-0.58779	-0.95106	-0.95106	-0.58779	-5.6836e-014	0.58779	0.95106	0.95106	0.58779	6.7617e-014	-0.58779	-0.95106	-0.95106	-0.58779	-7.8397e-014	0.58779	0.95106	0.95106	0.58779	-2.4509e-014	-0.58779	-0.95106	-0.95106	-0.58779	1.3728e-014	0.58779	0.95106	0.95106	0.58779	-2.9478e-015	-0.58779	-0.95106	-0.95106	-0.58779	-7.8328e-015	0.58779	0.95106	0.95106	0.58779	1.8613e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.9394e-014	0.58779	0.95106	0.95106	0.58779	4.0175e-014	-0.58779	-0.95106	-0.95106	-0.58779	-5.0955e-014	0.58779	0.95106	0.95106	0.58779	6.1736e-014	-0.58779	-0.95106	-0.95106	-0.58779	-7.2516e-014	0.58779	0.95106	0.95106	0.58779	-3.039e-014	-0.58779	-0.95106	-0.95106	-0.58779	1.9609e-014	0.58779	0.95106	0.95106	0.58779	-8.8286e-015	-0.58779	-0.95106	-0.95106	-0.58779	-1.952e-015	0.58779	0.95106	0.95106	0.58779	1.2733e-014	-0.58779	-0.95106	-0.95106	-0.58779	-2.3513e-014	0.58779	0.95106	0.95106	0.58779	3.4294e-014	-0.58779	-0.95106	-0.95106	-0.58779	-4.5074e-014	0.58779	0.95106	0.95106	0.58779	5.5855e-014	-0.58779	-0.95106	-0.95106	-0.58779	-6.6636e-014	0.58779	0.95106	0.95106	0.58779	7.7416e-014	-0.58779	-0.95106	-0.95106	-0.58779	2.549e-014	0.58779	0.95106	0.95106	0.58779	-1.4709e-014	-0.58779	-0.95106	-0.95106	-0.58779];
carry_f=5000;
%直接序列扩展频谱后的信号（BPSK调制）-----------
y=pn.*signal.*carry_signal; 

%计算信号功率Power_y ----------------
Power_y=dot(y,y)/N; 
%加性的服从正态分布的噪声randn()的功率  -------------从而可以确定信噪比
Pu=0.1  ;  
a=sqrt(12*Pu);                             
u=a*randn(1,N);

%仿真DS/SS信号----x------------------------------------------------------------
x=y+u;
subplot(311);
plot(x);

%开始对进行分析，以确定直扩信号y是否存在-------------
首先，对x进行FFT变换的频谱分析-----------
span_f=10*carry_f;
f=-span_f/2:span_f/N:span_f/2-span_f/N;
X=fft(x); 
subplot(312);
plot(f,fftshift(abs(X)));

%第二种：平方倍频法---------------------
y=x.*x;
subplot(312);
plot(y(1:N));
span_f=10*carry_f;
f=-span_f/2:span_f/N:span_f/2-span_f/N;
Y=fft(y); 
subplot(313);
plot(f,fftshift(abs(Y)));