一种基于调制m序列的直接序列扩频信号调制方法

A Signal Modulation Method of Direct Sequence Spread Spectrum Based on Modulated m-sequence

为提高直接序列扩频通信系统的频谱利用率,该文提出在m序列周期等于信息比特位宽整数倍情况下的直接序列扩频信号——调制m序列的信号调制与解调方法(m-DSSS)。首先结合调制m序列相关性数值仿真结果验证m-DSSS信号捕获可行性,然后根据信息比特的排列组合情况,设计一种基于多通道的m-DSSS信号调制和解调方法,并对m-DSSS信号通过加性高斯白噪声信道后的抗干扰能力建立数学模型。最后在相同频谱利用率条件下,与码移键控(CSK)调制方式进行了仿真对比试验。仿真结果表明,m-DSSS信号不仅比CSK信号具有更低的副峰,且当载波采用BPSK调制时,m-DSSS还可通过判断极性来辅助信号捕获,在误码率优于1e-3条件下,m-DSSS信号比CSK信号有2 dB以上优势,验证了m-DSSS调制用于直扩系统的可行性。

To raise the spectrum utilization,a modulation and demodulation method called modulated Direct Sequence Spread Spectrum(m-DSSS)is proposed,which assign the period of m-sequence to be equal to the integer multiple of data bit.Firstly,the feasibility of m-DSSS signal acquisition is verified by numerical simulation results of correlation.Then,according to the permutation of information bits,a multi-channel signal modulation and demodulation method for m-DSSS is designed,and the mathematical model reacting the antiinterference ability of passing through the additive Gaussian white noise channel is established.Finally,the simulation and contrast test are carried out with Codes Shift Keying(CSK)modulation under the same spectrum utilization.The simulation results show that m-DSSS signal not only has lower side peak than CSK signal but also can assist signal acquisition by judging polarity when BPSK modulation is adopted.When bit error rate is better than 1e-3,m-DSSS signal has more than 2 dB advantage than CSK signal,which verifies the feasibility of m-DSSS used in DSSS system.