TABLE OF CONTENTS In Chapter 1, applications that require synthesizers were introduced. This was done to provide background and motivation for the rest of this text, which is devoted to the details of making these circuits work. In this chapter, overviews of system-level configurations incorporating these circuits will be given. This will set the stage for the rest of the book, in which these systems will be examined in progressively more detail. Additional general information on synthesizers can be found in [1 21].
An integer- N PLL is the simplest type of phase-locked loop synthesizer and is shown in Figure 2.1. Note that N refers to the divide-by- N block in the feedback of the PLL. The two choices are to divide by an integer (integer- N) or to divide by a fraction (fractional- N), essentially by switching between two or more integer values such that the effective divider ratio is a fraction. PLL-based synthesizers are among the most common ways to implement synthesizers, and this area is the subject of a great deal of research and development [22 54]. The PLL-based synthesizer is a feedback system that compares the phase of a reference f r to the phase of a divided-down output of a controllable signal source f fb, also known as a voltage-controlled oscillator (VCO). The summing block in the feedback is commonly called a phase detector. Through feedback, the loop forces the phase of the signal source...
