Signal Integrity Issues and Printed Circuit Board Design

Appendix I. TDRs and VNAs

It is not uncommon now to read an article or see a presentation with references to a time domain reflector (TDR) analysis or to see a graph of an analysis based on a TDR response. Less commonly we are beginning to see references to similar analyses with vector network analyzers (VNAs). Many designers have never had the opportunity to learn what these tools do or how they work. This appendix gives an overview of the operating principles behind the tools so you can at least understand what it is they are able to show.

Basic Concepts

In one sense, the operating principles behind TDRs and VNAs are almost identical. They have very similar block diagrams, analyze the same circuits, and give equivalent results. Both are used to ...