非周期长码直扩信号的长扰码识别

该文利用m序列的二阶和三阶自相关特性，推导得到非周期长码直扩信号三阶自相关函数的极大似然估计，利用m序列的线性移位叠加特性和三阶自相关函数特性，提出了非合作通信情况下消除信息码对长码估计影响的延迟相乘方法和基于三阶自相关峰的长码识别算法，该识别算法只需已知信号的载波频率和扩频码码片速率。在加性高斯白噪声下的仿真表明，仅利用1/4倍长码周期长度的信号，在信噪比大于3.5 dB时长码m序列的正确识别概率就达到90%以上。

An Identification Method of Long Pseudo-random Code Sequence in Non-periodic Direct Sequence Spread Spectral Signals

Using the second-order and third-order autocorrelation characteristics of m sequences, the maximum likehood estimation for the triple autocorrelation function of the Non-Periodic Long Code Direct Sequence Spread Spectral (NPLCDS-SS) signals is deduced. By utilizing the shift-and-add property and the triple autocorrelation characteristics of m sequences, the influence of the information code on the estimation is eliminated by the processing of delay and multiplication, a identification method for long code is proposed based on the peaks of the triple autocorrelation function in a non-cooperative communication with the certain carrier frequency and chip width of spreading code. Simulations under additive white Gaussian noise show that the correct identification probability of the algorithm is above90% when a quarter of the cycle length of the long PN code signal is used only and the signal-to-noise ratio is greater than 3.5 dB.