This paper discusses different approaches to improve the settling behavior of phase lock loops (PLL). Starting with a state-of-the-art PLL, a structure with an additional dynamic changing Loop-Filter and another structure with feed forward control are proposed. The main topic of this paper is the adaption of modern control theory in the design of PLL systems to improve reference action of the control loop. For both structures, the block diagram of the two approaches are presented and then advantages and difficulties are discussed. Both methods are compared to the state-of-the-art by simulations in MatLab Simulink. Therefore a large change of frequency is requested from the PLL and the corresponding time for locking is analyzed. All in all both novel PLL concepts promise reduced settling times with respect to a specified change of the PLL output frequency.