20 DESIGN007 MAGAZINE I DECEMBER 2019
• The distributed system model is more
accurate but also more complex than the
lumped element model
• Traces longer than one-tenth wavelength
will usually need to be analyzed as a
distributed system
• The technology employed and the physi-
cal scale of the design is also significant as
miniaturized circuits can use the lumped
model at a higher frequency
• Lumped element designs generally result
in a smaller product
• The distributed model for transmission
lines starts deviating from the simplified
lumped element model between a trace
length of 0.01 and 0.1 of the wavelength
of the signal
Further Reading
• B. Olney, "Beyond Design: Controlled Im-
pedance Design," The PCB Design Maga-
zine, May 2015.
• B. Olney, "Beyond Design: Transmission
Lines—From Barbed Wire to High-speed
Interconnects," The PCB Design Magazine,
May 2014.
• B. Olney, "Beyond Design: Effects of Sur-
face Roughness on High-speed PCBs," The
PCB Design Magazine, February 2015.
• B. Olney, "Beyond Design: Common
Symptoms of Common-mode Radiation,"
Design007 Magazine, May 2018.
• Arthur Anderson, "Transmission Lines:
From Lumped Element to Distributed
Element Regimes," All About Circuits,
November 28, 2015.
• E. Bogatin, Signal and Power Integrity:
Simplified, Prentice Hall, 2008.
Editor's note: All figures drawn by Barry Olney.
Barry Olney is managing director
of In-Circuit Design Pty Ltd. (iCD),
Australia, a PCB design service
bureau that specializes in board-
level simulation. The company
developed the iCD Design Integ-
rity software incorporating the iCD
Stackup, PDN, and CPW Planner. The software can be
downloaded www.icd.com.au. To read past columns or
contact Olney, click here.
