笔记本电脑的电磁干扰控制.docVIP

——————————————————————————————————————————————— 笔记本电脑的电磁干扰控制 TECHNICAL REPORTS Design Technologies for Low-EMINotebook Personal Computers by Dr. Eishi Gofuku and Shinji Tanabe* Advances in computer science and hardware inrecent years have made possible three-dimen-sional simulations of electromagnetic interfer-ence (EMI) phenomena. We at MitsubishiElectric have developed a simulator and are nowutilizing it to analyze the relationship of radia-tion intensity to current densities in printedcircuit boards (PCBs) and the structure of liq-uid-crystal displays (LCDs); the results of whichare applied to product design. This represents anew direction for research. In this paper, we describe LCD designs to re-duce emission noise, drawing on measurementresults obtained using a three-dimensional elec-tromagnetic field simulator (MAGNA/EMI)based on a finite element method and devel-oped jointly by Mitsubishi Electric’s AdvancedTechnology Ramp;D Center and the CRC ResearchInstitute. Background The sizes of LCD devices have become largerand the picture quality has improved. This hasled thin-film transistor (TFT)-LCDs to domi-nate as the display for “notebook” personalcomputers (PCs). Since high-speed digital pro-cessing is necessary for image display, the ra-dio-frequency components of such signals are,to a greater or lesser extent, radiated away fromthe display as an RF noise. Standards (tolerances) have been establishedin order to prevent this undesirable radiation.Nearly all such standards conform to or arebased on international standards established bythe International Special Committee on RadioInterference (CISPR). CISPR 22 (2nd edition) is,in effect, an international passport for electronicproducts where electromagnetic emissions areconcerned; for manufacturers of electronic equip-ment, meeting the standards and regulationsfor EMI is absolutely essential if their productsare to have free entry to overseas markets.Electromagnetic Field Analy