This book is intended for the graduate or advanced undergraduate
engineer. The primary motivation for developing the text was to present a
complete tutorial of phase-locked loops with a consistent notation. I believe
this is critical for the practicing engineer who uses the text as a self-study
guide.
Three years after the first printing, I discovered there was a need for a
second edition. I had taught several short courses from the text, and
discovered that today’s engineers needed less time devoted to discrete-time
theory, but wanted more practical information on implementing phase-locked
loops. As a result, I have deleted discussions on topics such as multi-rate
sampling and the Jury test, and replaced them with new content. Included in
the new material are additional loop filters and reduction of reference feedthrough in frequency synthesizers. Indeed, frequency synthesis is itself a
new topic in the text.
Since most hardware phase-locked loops utilize charge pumps, I
developed a new chapter that spotlights charge pumps and its complementary
sequential phase detector. Several students in the short courses were asking
for design examples on delay-locked loops used to synchronize circuits on
CPUs and ASICS. The second printing includes new material for this very
purpose.
Another change was the increased use of Many of the original graphics have been replaced with graphics generated by MATLAB’s or Control System Toolbox. Since MATLAB has emerged as the leading simulation tool for the communications engineer, the graphics should be familiar and provide more information such as gain and phase margins. I have also taken the opportunity to correct typographical errors
and further improve the consistency in notation.
New material has been added on digital dividers. These devices can
easily dominate a frequency synthesizer’s noise floor, but the literature has
not provided many solutions. In this second edition, I added sections
discussing the origin of phase noise in digital dividers and possible solutions.
Also included are some techniques to analytically estimate the phase noise of
a divider before it is even fabricated.
In the past year, many students in the short courses have been asking for
design help on optical phase-locked loops. A new chapter has been added on
this topic. Because many designers will be new to optical communications, I
have included short sections discussing components such as lasers and
photodetectors. Since coherent phase-locked loops are so very difficult to
implement, I have included a section on automatic frequency control to
provide frequency-locking of the lasers instead of phase-locking.
This second edition begins with the early history of phase-locked loops. I
believe that historical knowledge can provide insight to the development and
progress of a field, and phase-locked loops are no exception. Although allanalog
phase-locked loops are becoming atypical, the continuous-time nature
of analog loops allows an easy introduction to phase-locked loop theory.
This foundation then allows us to proceed to the many implementations and
discussions of phase-locked loops.
I wish to thank the readers of the first edition for their many suggestions
and comments. Likewise the short course students have also strengthened
this new edition with their participation and comments. I have tried to
incorporate these suggestions within the intended scope of the text.