New Nonlinear Second-Order Phase-Locked Loop with Adaptive Bandwidth Regulation

Lei Zhao,Congying Zhu,Lei Shi

doi:10.3390/electronics7120346

Lei Zhao, Congying Zhu + Show 1 more

Open Access

https://doi.org/10.3390/electronics7120346

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Abstract

Synchronization of large acquisition bandwidth brings great challenges to the traditional second-order phase-locked loop (PLL). To address the contradiction between acquisition bandwidth and noise suppression capability of the traditional PLL, a new second-order PLL coupled with a nonlinear element is proposed. The proposed nonlinear second-order PLL regulates the loop noise bandwidth adaptively by the nonlinear module. When a large input–output phase error occurs, this PLL reduces the frequency offset quickly by taking advantage of the large bandwidth. When the phase error is reduced by the loop control, the proposed PLL suppresses noises by using the small bandwidth to increase the tracking accuracy. Simulation results demonstrate that the tracking speed of the proposed PLL is increased considerably, and its acquisition bandwidth is increased to 18.8 kHz compared with that of the traditional second-order PLL (4 kHz).

Highlights

Phase-locked loop (PLL) is widely applied in synchronization of communication systems as a phase follow-up system [1,2,3]
An irreconcilable contradiction exists between the tracking speed and accuracy of the traditional second-order phase-locked loop (PLL), and this contradiction is an important consideration in engineering applications [6,16]
It is mainly composed of three parts [24]: (1) phase discriminator (PD), (2) loop filter (LP), and (3) voltage-controlled oscillator (VCO) (Figure 1a)

Summary

Introduction

Phase-locked loop (PLL) is widely applied in synchronization of communication systems as a phase follow-up system [1,2,3]. The loop is generally designed with a small bandwidth to realize normal operation of the PLL under low signal-to-noise ratio, but this loop has poor dynamic adaptability [9,10,11]. In this study, both noise rejection and fast locking performance are required aspects for the PLL with regard to the area of synchronous receiving highly dynamic telemetry or GPS signals. The PLL based on the Kalman filter can still maintain the locking state under serious scintillation

Methods

Results

Conclusion