Common-mode currents induced on cables attached to printed circuit boards (PCBs) can be a significant source of unintentional radiated emissions. This paper develops a model for estimating the amount of common-mode cable current that can be induced by the signal voltage on microstrip trace structures or heatsinks on a PCB. The model employs static electric field solvers or closed-form expressions to estimate the effective self-capacitances of the board, trace, and/or heatsink. These capacitances are then used to determine the amplitude of an equivalent common-mode voltage source that drives the attached cables. The model shows that these voltage-driven common-mode cable currents are relatively independent of the cable parameters and the trace or heatsink location when the PCB is small relative to the cable length and to a wavelength.


Electrical and Computer Engineering

Keywords and Phrases

Absolute Capacitance; PCB; Cables (Electric); Common-Mode Cable Current; Common-Mode Voltage Source; Current-Driven Radiation; Electric Fields; Heat Sinks; Heatsinks; Microstrip Trace Structures; Printed Circuit Board; Printed Circuits; Radiated Emission Estimation; Radiated Emissions; Radiation By Attached Cables; Static Electric Field; Voltage-Driven Common-Mode Cable Currents; Voltage-Driven Radiation; Wire Antenna

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2005 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jan 2005