Dual reference frequencies for low spur and low phase noise fractional- N frequency phase locked loop

The fractional-N phase lock loop has been widely used in wireless communication systems due to the high frequency resolution and the short locking time. The spur and the phase noise are two main performances of this kind of phase locked loop, but it is very difficult to reach both of the low spur and the low phase noise. The paper describes the new structure with dual reference frequencies to solve the problem.