Common-mode current due to a trace near a PCB edge and its suppression by a guard band

Yoshiki Kayano, Motoshi Tanaka, James L. Drewniak, Hiroshi Inoue

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


The common-mode (CM) current due to a trace near a printed circuit board (PCB) edge, and its suppression by a guard band have been studied experimentally and with finite-difference time-domain (FDTD) modeling. As the guard band, copper tape is connected along the entire edge of the ground plane. First, a PCB electromagnetic interfercnc (EMI) coupling path that results from the nonzero impedance of the PCB ground plane is discussed. As the trace is moved closer to the PCB edge, the CM current increases. Then, the effect of the guard band on the CM current is detailed. A guard band parallel to and near a trace is most effective in suppressing the CM current. The cross-sectional magnetic Held distribution at center of the PCB with and without the guard band is also calculated with FDTD modeling. The guard band decreases the magnetic field distributed on the reverse side of a PCB. These results indicate the guard band is effective in suppressing CM current. Finally, an empirical formula to quantify the relationship between the position of a trace and CM current for the case with a guard band is proposed. Calculated results using the empirical formula and FDTD modeling are in good agreement, which indicates this empirical formula should be useful for developing EMI design guidelines.

Original languageEnglish
Pages (from-to)46-53
Number of pages8
JournalIEEE Transactions on Electromagnetic Compatibility
Issue number1
Publication statusPublished - 2004 Feb
Externally publishedYes


  • Common-mode (CM) current
  • Electromagnetic interference (EMI)
  • Finite-difference time-domain (FDTD) method
  • Guard band
  • Printed circuit board (PCB)

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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