A Passive Third-Order Cascade PLL Filter
In this paper, the traditional passive loop filter is improved, and a new type of Cascade Third-order filter structure and Graphical Phase Design method is proposed, which greatly simplifies high-order PLL filter’s design, analysis and calculation. According to graphical phase design principle, parameters for cascade third-order filter could be figured out from the given formula, the derived result is simulated in the form of Bode plots and Unit-step response with Pspice software and the loop target under different parameters is compared. Experiments show that this third-order filter could significantly improve the stability of PLL, deeply attenuate the phase detector’s high-frequency noise and is well adapted to the loop gain change. Users can also change the design parameters flexibly according to the system requirements with this filter.
L. Feng et al., "A Passive Third-Order Cascade PLL Filter", Advanced Materials Research, Vols. 255-260, pp. 2262-2266, 2011