高动态非线性调频直扩信号的伪码快捕算法

针对高动态非线性调频直接扩频(NLFM-DSS,nonlinear frequency modulation direct spread spectrum)信号伪码捕获的问题,提出一种基于离散多项式相位变换(DPT)的NLFM-DSS信号伪码快捕算法.首先通过瞬态矩确定信号的阶数,并将信号降阶成带残余频偏的直扩信号.然后采用PMF-FFT与功率谱相结合的方法实现伪码快速捕获.给出了基于该算法的信号模型和理论分析表达式,并通过计算机仿真验证了该方法的可行性,在扩频增益为1023时,利用功率谱非相关累积30次,可在信噪比为-20 dB时捕获到伪码.

Fast Acquisition Algorithm of PN Code for High Dynamic NLFM-DSS Signal

For the problem of the acquisition of PN code for high dynamic NLFM-DSS (nonlinear frequency modulation direct spread spectrum) signal,the method based on discrete polynomial-phase transform (DPT) is presented.Firstly,through transient torque to calculate the order of the NLFM-DSS signal,and the order is reducted to only one,so the NLFM-DSS signal can be transformed into a new PN code multiplied by sine and the new noise,that is with the residual carrier frequency offset in direct sequence spread spectrum (DSSS) signal.And then,the algorithm based on partial correlation and cumulative power spectral is used to capture the signal.The algorithm based on the signal model and the analytical expression is presented,and the feasibility of the method is verified by the computer simulation.When the spreading gain is 1023,and non-related accumulation by power spectrum is 30 times,the method can capture the PN code at the -20dB SNR.