论文部分内容阅读
As one of the high‐performance receiver,high sensitivity receiver has gradually become a research hotspot in recent years.Increasing the PDI time can improve SNR (Signal to Noise Ratio) to track the weak signal on one hand,and reduce data rate and operand on the other hand,but it needs to consider the effect of data bits jump.BeiDou Navigation Satellite System (BDS) broadcasts D1 NAV message on B1I signal.D1 NAV message is modulated with 1 kbps secondary code of Neumann‐Hoffman (NH) code,which can improve suppression of narrow‐band interference and the cross correlation characteristic of satellite signals.Meanwhile,the NH code limits the pre‐detection integration (PDI) time to be 1ms.So that,to track the weak signal availably,the NH code must be solved to increase the PDI time.The common method so‐called sliding correlation method is influenced by data bit jumps.A method of Bit synchronization which can also solve NH code and data bit jumps is designed,by using bits matching method in groups.Using the QuartusII 7.2 software,the method of Bit synchronization is designed.The simulation results show that the bit synchronization method is able to achieve signal synchronization stably and reliably.By bit synchronizing and NH code solving,the PDI time can be the maximum 20ms and it willlay the foundation for the further research and application of weak signal tracking sensitivity.