四相鉴频器辅助的高动态BOC信号载波跟踪

叉积鉴频器的输出频率范围比较窄,捕获信号以后的多普勒频偏可能不在其跟踪范围内。针对此问题,提出了使用四相鉴频器（FQFD）算法辅助已经成型的二阶锁频环加三阶锁相环模型。首先,利用四相鉴频器的非线性特性将接收信号频偏大步长牵引到较低范围,然后使用锁频环消除其大部分动态性,最后利用锁相环跟踪精度高的特点实现高动态二进制偏移载波(Binary Offset Carrier,BOC)信号载波的快速准确跟踪。在分析各跟踪模块算法的基础上,讨论了其本身的热噪声误差、动态适应力以及最优带宽等相关问题,理论分析和仿真结果验证了该方法比原有跟踪算法提高了300 Hz左右的鉴频范围,并且跟踪效果良好。

Carrier tracking of high dynamic BOC signal based on four-quadrant frequency discriminator

For a relatively narrow output frequency range of cross-product discriminator,Doppler shift may not meet its tracking range after capturing the signal.In view of this problem,this paper proposes an algorithm which uses Four-Quadrant Frequency Discriminator(FQFD) to assist mature second-order frequency locked loop(2nd FLL) and third-order phase locked loop(3rd,PLL) model. Firstly,frequency offset of the received signal is drawn to the lower range by using the nonlinear characteristic of the FQFD,and then the FLL is used to eliminate most of the dynamics.Finally PLL with high tracking accuracy is applied to realize the carrier tracking of high dynamic binary offset carrier(BOC) signal rapidly and accurately. According to the analysis of each tracking module algorithm,its own thermal noise error and dynamic adaptability are discussed as well as the optimal bandwidth and other related issues. The theoretical analysis and simulation results show that this method increases about 300 Hz frequency range compared with the original tracking algorithm and it also has a good tracking performance.