Design And Verification Of Phase-Locked Loops With Peaking-Free Loop Filter

Phase-locked loops are a basic device in wireless mobile communication system,and the fast locking performance is important in high speed frequency hopping communication system.When the phase-locked loops works,the overshoot in the transient response will slow down the locking process of the loop,which is an important reason to affect the locking time.In the existing scheme,the transient overshoot is usually eliminated by the feedback delay link or the programmable frequency divider.However,the optimization results of locking time are not ideal,and there are some problems such as complicated circuit structure,timing jitter and mismatching.To solve above problems,this paper puts forward a loop filter is introduced in the negative feedback method,is used to eliminate the Phase-locked loops closed-loop transfer function of zero,thereby eliminating the transient overshoot,achieve the goal of speed loop lock.Contrast has to eliminate the transient overshoot of method,this paper puts forward the method not only has faster speed,and has some advantages such as simple circuit structure and low timing jitter,and matching the characteristics of high,so has certain advantages.According to the importance of the Phase-locked loops to realize rapid locking,the influence of transient overshoot on locking time of phase-locked loops is laid special stress on analyzed,to a second order proportional integral loop filter based phase-locked loops as an example,analyzes the cause of the transient overshoot,and put forward a kind of used to eliminate the transient overshoot achieve rapid locking phase-locked loops method.The transfer function of the unit step response of the phase-locked loops is derived by analyzing the S domain model of the non-transient overshot phase-locked loops.Firstly,the Simulink model in Matlab verifies that the transfer function has no transient overshoot.Then use UMC 55 nm in Cadence to set up the standard CMOS technology based on without a filter circuit structure of the phase lock circuit,implements the design of the circuit and the corresponding experimental results are obtained by Spectre simulation.The simulation results show that the calculation results of the formula in the design scheme are consistent with the Simulink and Spectre simulation results under the working voltage of 1.2 V.By comparing the existing charge pump phase-locked loops of the step transient response,this paper designs without the transient overshoot of phase-locked loops by eliminating the transient overshoot,the locking time mu s decreased from 3.12 ?s to 1.67?s,46.47%of locking time was optimized.The experimental results show that the design method can be used in fast locking phase-locked loops,and it has a certain application prospect in high speed frequency-hopping communication system.