The electric fields that couple traces on printed circuit boards to attached cables can generate common-mode currents that result in significant radiated emissions. Previous work has shown that these radiated emissions can be estimated based on the self-capacitances of the microstrip structures on a board . In general, the determination of these self-capacitances must be done numerically using three-dimensional static modeling software. In this paper, an approximate closed-form expression for the self-capacitance of microstrip traces is derived. This expression can be used to estimate the voltage-driven common-mode emissions from boards with various microstrip trace geometries. The expression also provides insight relative to the microstrip parameters that have the greatest effect on radiated emissions.


Electrical and Computer Engineering

Keywords and Phrases

Absolute Capacitance; Approximate Closed-Form Expression; Common-Mode Current; Electric Fields; Microstrip Traces; Printed Circuit Board Trace; Printed Circuits; Radiated Emissions; Self-Capacitance; Voltage-Driven Common-Mode Emissions; 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