Abstract:

Establishing the loops mathematic module, the phase tracking error equation of the second-order frequency locking loop(FLL) assisted third-order phase locking loop(PLL) is derived. In the module, the tracking error of FLL is mixed into PLL. Two points of view are given: firstly, the phase dynamic tracking error of frequency locking loop assisted PLL(FPLL) is equal to zero in case of jerk; the phase thermal noise tracking error includes the thermal noise of PLL and the noise component of FLL, secondly, a new optimization method is proposed to optimizing both bandwidths of PLL and FLL. The optimization method minimizes the total phase tracking error to meet the need of constraint of FLLs frequency tracking error being within the PLLs locking bandwidth. Simulation shows that the analysis of phase tracking error is accurate; the optimization method is able to improve the tracking accuracy while being stable. This research will help the later extra design of FPLL.

Key words: frequency locking loop assisted phase locking loop, performance analysis, optimization method