Effect of Conductive Sheet Placed over PCB on Electromagnetic Noise Shielding

Motoshi TANAKA  Hisashi TAKITA  Hiroshi INOUE  

IEICE TRANSACTIONS on Communications   Vol.E86-B   No.3   pp.1125-1131
Publication Date: 2003/03/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electromagnetic Compatibility(EMC)
electromagnetic noise,  conductive sheet,  PCB,  shielding,  FDTD method,  

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The effect of a conductive sheet placed over a PCB with a microstrip line on electromagnetic noise shielding is investigated. As a typical conductive sheet, a copper sheet is used, and is not grounded. First, the input impedance of the microstrip line and the magnetic field when varying the distance between the PCB and the conductive sheet are measured, and the distance that does not affect the signal transmission is set at 8 mm. Second, the effect of the conductive sheet size on the magnetic field radiation is discussed by measurements and FDTD modeling, and the magnetic near-field distribution around the PCB is visualized by using the FDTD calculation. A conductive sheet whose width is larger than the PCB width should be effective for suppression of the magnetic near-field noise radiation just above a PCB.