-
-
News
News Highlights
- Books
Featured Books
- design007 Magazine
Latest Issues
Current IssueAll About That Route
Most designers favor manual routing, but today's interactive autorouters may be changing designers' minds by allowing users more direct control. In this issue, our expert contributors discuss a variety of manual and autorouting strategies.
Creating the Ideal Data Package
Why is it so difficult to create the ideal data package? Many of these simple errors can be alleviated by paying attention to detail—and knowing what issues to look out for. So, this month, our experts weigh in on the best practices for creating the ideal design data package for your design.
Designing Through the Noise
Our experts discuss the constantly evolving world of RF design, including the many tradeoffs, material considerations, and design tips and techniques that designers and design engineers need to know to succeed in this high-frequency realm.
- Articles
- Columns
- Links
- Media kit
||| MENU - design007 Magazine
Estimated reading time: Less than a minute

Beyond Design: Impedance Matching: Terminations
The impedance of the trace is extremely important, as any mismatch along the transmission path will result in a reduction in signal quality and possibly the radiation of noise. Mismatched impedance causes signals to reflect back and forth along the lines, which causes ringing at the load. The ringing reduces the dynamic range of the receiver, eats into the noise budget and can cause false triggering.
Reflections occur whenever the impedance of the transmission line changes along its length. This can be caused by unmatched drivers/loads, layer transitions, different dielectric materials, stubs, vias, connectors and IC packages. By understanding the causes of these reflections and eliminating the source of the mismatch, a design can be engineered with reliable performance. For perfect transfer of energy and to eliminate reflections, the impedance of the source must equal the impedance of the trace, as well as the impedance of the load. When the signal path has an impedance discontinuity, place a terminator at the point of line discontinuity to equalize the impedance.
Editor's Note: This column originally appeared in the October 2013 issue of The PCB Design Magazine.
More Columns from Beyond Design
Beyond Design: The Metamorphosis of the PCB RouterBeyond Design: Radiation and Interference Coupling
Beyond Design: Key SI Considerations for High-speed PCB Design
Beyond Design: Electro-optical Circuit Boards
Beyond Design: AI-driven Inverse Stackup Optimization
Beyond Design: High-speed Rules of Thumb
Beyond Design: Integrated Circuit to PCB Integration
Beyond Design: Does Current Deliver the Energy in a Circuit?