This paper examines the measured power bus impedance of fully populated 4-layer printed circuit boards with internal power and ground planes. Three boards provided by two leading computer companies were evaluated. Each of the state-of-the-art high-speed boards used in this study employed surface-mount decoupling capacitors to reduce noise on the power bus. The boards were measured with and without some or all of their decoupling capacitance. The effectiveness of the decoupling capacitors as a function of location and frequency and the relationship between board impedance and power bus noise was explored. The behavior of 4-layer boards is shown to be quite different than that of boards without planes or boards with closely spaced planes.

Meeting Name

IEEE International Symposium on Electromagnetic Compatibility (1995: Aug. 14-18, Atlanta, GA)


Electrical and Computer Engineering

Research Center/Lab(s)

Electromagnetic Compatibility (EMC) Laboratory

Keywords and Phrases

4-Layer Printed Circuit Board Decoupling; Capacitors; Electric Impedance Measurement; Electric Noise Measurement; Experimental Investigation; Frequency; Ground Planes; High-Speed Boards; Internal Power; Location; Measured Power Bus Impedance; Noise Reduction; Power Bus Noise; Printed Circuit Testing; Surface Mount Technology; Surface-Mount Decoupling Capacitors

International Standard Book Number (ISBN)

0780325737; 0780336089

International Standard Serial Number (ISSN)


Document Type

Article - Conference proceedings

Document Version

Final Version

File Type





© 1995 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Aug 1995