Analysis on Phase Lock Loop with frequency and phase dual assistance

In order to meet the contradictory needs coming from dynamic and tracking accuracy, a novel 2-order Phase Lock Loop (PLL) with frequency and phase dual assistance is proposed based on the introduction of DFT phase difference algorithm. The frequency estimation is used to set the center frequency of NCO to make the PLL work in fast pull-in range. According to the estimation accuracy and the relationship between fast pull-in range and loop bandwidth, the lower limit of loop bandwidth is derived. Meanwhile the phase assistance improves the transient response of PLL, which shortens the transient process much further. Theoretical analysis and Simulation results indicate the proposed assistance scheme ensures that the PLL can synchronize quickly and accurately.