Beyond Design: Faster than a Speeding Bullet


Reading time ( words)

In a previous Beyond Design column, Transmission Lines, I mentioned that a transmission line does not carry the signal itself, but rather guides electromagnetic energy from one point to another. The speed of a computer does not depend intrinsically on the speed of electrons, but rather on the speed of energy transfer between electronic components. Electron flow in a multilayer PCB is extremely slow—about 10 mm per second—so, how does the signal travel so fast, how fast does it actually transfer information and what are the limitations?  

In optical communications, electrons don’t carry the signal—photons do. And we all know that photons travel at the speed of light. So surely, optical fibers must transmit information much faster than copper wires or traces on a multilayer PCB? Actually, photons and electrons transmit data at the same speed. The limiting factor is the relative permittivity (dielectric constant) of the medium in which the signal propagates. 

An optical fiber is a cylindrical dielectric waveguide made of low-loss materials such as fused silica glass. It has a central core in which light is guided, and embedded in an outer cladding of slightly lower refractive index. The silica glass used has a dielectric constant (Er or Dk) = 3.78 @25GHz. Whereas, for instance, Panasonic’s new Megtron 7, low Dk, glass PCB laminate has an Er = 3.3 at the same frequency. 

To read this entire article, which appeared in the February 2016 issue of The PCB Design Magazine, click here.

Share


Suggested Items

Julie Ellis: TTM’s Interface Between Designer and Fabricator

04/04/2018 | Barry Matties, Publisher, I-Connect007
As a field application engineer for TTM, Julie Ellis sees the problems that can occur between circuit board designers and manufacturers. Barry Matties spoke with Julie at the AltiumLive event in Munich about the age-old problem of throwing designs “over the wall,” the trend towards HDI, and what advice she would give new designers.

South African Electronics Industry Going Strong

04/03/2018 | Barry Matties, I-Connect007
EDA Technologies is a South African company that offers PCB design engineering services, mainly for the domestic electronics market, which makes up a surprising 12.5% of South Africa’s GDP. Barry Matties recently spoke to founder Nechan Naicker about the benefits of outsourcing to South Africa, the market segments they service there, and any advice he had to offer from his 20+ years in the industry.

Part 2: EIPC’s 2018 Winter Conference in Lyon, Review of Day 1

02/19/2018 | Pete Starkey, I-Connect007
We continue with the rest of Pete Starkey’s report on Day 1 of the EIPC Winter Conference in Lyon, France. Included in this segment are presentations by Ventec, Ericsson, TTM and others, plus photos of their evening tour of Alstom.



Copyright © 2018 I-Connect007. All rights reserved.