Research And Design Of An Adaptive-Bandwidth All Digital Phase-Locked Loop Based On Fuzzy Control Algorithm

With the wide application of phase-locked loop in the area of electronic technology, the demand of the properties and the level of integration of phase locked-loop are higher and higher. The traditional fixed bandwidth phase-locked loop can't satisfy the engineering need. The bandwidth adaptive phase-locked loop can solve the inter-constraint problem of phase lock bandwidth and anti-noise performance of the analog loop system very well. Along with the rapid development of digital electronic technology, the digital locked-loop gradually takes place of analog phase-locked loop. The digital phase-locked loop can track the input signal in a very short time, having high performance of anti-noise and high level of integration. It can not only be made into integrated phase-locked loop, but also can be embedded as a function module on the chip. However, the birth of the digital phase-locked loop can't solve the fundamental problems in the design of PLL. The design of all digital phase-locked loop has many difficulties, such as the difficulties in designing nonlinear system and realizing low-pass filter. The decoupling control of the locked scope, locked speed and the stability also has some difficulties.According to the existing problems in the design of all digital phase-locked loop, the advantage of fuzzy control algorithm in designing nonlinear system is used to design the adaptive-bandwidth all digital phase-locked loop. A novel design method based on fuzzy control algorithm is proposed to design the adaptive-bandwidth all digital phase locked-loop. Based on the model of adaptive bandwidth all digital phase-locked loop based on PI algorithm, combining with the adaptive bandwidth criterion, the existing model of adaptive bandwidth all digital phase-locked loop system is improved. A new model based on fuzzy control algorithm is established. Through the theoretical research, the connections between the single side noise bandwidth BL and the parameters of the low pass filter can be found out. On the basis of theoretical study, a new kind of fuzzy bandwidth controller is designed. The controller has two inputs: phase error and angular error. The output of the fuzzy controller is the single side noise bandwidth BL. Through BL the loop filter parameters can be adjusted in order to realize adaptive phase tracking. The design and simulation of the second order phase locked loop circuit are finished by modeling in the DSP Builder. Based on the simulation, transform the model built in DSP Builder into VHDL program. The fuzzy control algorithm is realized in FPGA. The structure and function of each module is realized by using the idea of modular design. Finally, the functional simulation and time-series simulation of the system is realized, using EDA tools.The simulation results show that the design method of all digital phase-locked loop based on the fuzzy control algorithm can realize adaptive bandwidth adjustment. When the external signal fluctuated in wide range, the loop system can lock the signal quickly. Moreover, compared with the traditional adaptive bandwidth all digital phase-locked loop based on PI control algorithm,the adaptive bandwidth all digital phase-locked loop based on fuzzy control algorithm,the system stability and response speed is much better.