Advanced Frequency Synthesis by Phase Lock

CHAPTER 6

SIMULATION

Much of our discussion to this point has been based on Simulink^® models. These have been used to explain fundamental relationships in the ΣΔ synthesizers and to expose performance defects (but without attempting to model all the circuit imperfections and limitations in a real synthesizer). A collection of models is provided online for use in further study and for expansion to represent additional effects and to answer new questions. Here we will discuss these models and some MATLAB^® scripts that have been used as well.

We will depend on the Simulink Users Guide and Help documents to explain the details of using the Simulink program to those who are not familiar with it; we will concentrate on the information that is unique to our models and simulations.³⁹ The models and scripts must be downloaded (Appendix W) and put into a directory that is included in the MATLAB search path (Command Window/File/Set Path…) in order to be accessed by the Simulink or MATLAB program. Required block sets, and toolboxes required for MATLAB scripts, are given in Appendix T.

Our first model description will include many items that are carried over to other models and which will not be discussed again.

6.1   SandH.mdl

The early parts of Chapter 2 use the Simulink model SandH.mdl shown in Fig. 6.1.

FIGURE 6.1   S&H.mdl.

6.1.1   The Synthesizer Loop

The “Continuous Time VCO,” which ...