tailieunhanh - Báo cáo hóa học: " Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay | EURASIP Journal on Wireless Communications and Networking 2005 3 413-418 2005 Qassim Nasir Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay Qassim Nasir Department of Electrical and Computer Engineering College of Engineering University of Sharjah P. O. Box 27272 Sharjah UAE Email nasir@ Received 7 November 2004 Revised 21 May 2005 Recommended for Publication by Jonathon Chambers The input frequency limit of the conventional zero-crossing digital phase-locked loop ZCDPLL is due to the operating time of the digital circuitry inside the feedback loop. A solution that has been previously suggested is the introduction of a time delay in the feedback path of the loop to allow the digital circuits to complete their sample processing before the next sample is received. However this added delay will limit the stable operation range and hence lock range of the loop. The objective of this work is to extend the lock range of ZCDPLL with time delay by using a chaos control. The tendency of the loop to diverge is measured and fed back as a form of linear stabilization. The lock range extension has been confirmed through the use of a bifurcation diagram and Lyapunov exponent. Keywords and phrases nonuniform sampling digital phase locked loops chaos control. 1. INTRODUCTION Digital phase locked loops DPLLs were introduced to minimize some of the problems associated with the analogue loops such as sensitivity to DC drift and the need for periodic adjustments 1 2 . The most commonly used DPLL is the zero-crossing digital phase-locked loop ZCDPLL . The ZCDPLL operation is based on nonuniform sampling techniques. The loop is simple to implement and easy to model. The ZCDPLL consists of a sampler that acts as phase detector digital filter and digital-controlled oscillator DCO . In the ZCDPLL there is a limit on the frequency of the incoming signal beyond which the loop ceases to function properly any longer. This limit is reached when the period