臺灣博碩士論文加值系統

摘 要
隨著科技的進步，電子產品的速度與效能也不斷的提升，越來越快的效能與速度相對的也衍生出了彼此之間電磁波輻射干擾的問題， 為了減少產品所產生的電磁輻射相互干擾，電磁相容EMC的相關法規也成為產品量產出貨前的重要認證之一。
在這篇論文中，我們提出一個有關解決EMI輻射干擾之對策的一個新的觀念和方向，大多數電子設備的硬體都包含一些零件，它們都具有類似天線的特性，例如電纜、印刷電路板佈線、內部連接線及機構等。我們運用了多種EMI對策的方法：
1. 接地(0 V 參考平面) 系統的改善。
2. 在恰當的位置運用濾波器和EMI抑制元件。
3. 印刷電路板的佈局和規劃。
以上方法使我們在抑制EMI的電磁波輻射干擾(RFI)方面不須用到金屬遮蔽裝置的方式，且成功的實現在19�c LCD-TV 上，並且符合EMC法規的要求。在這篇論文中，我們不僅降低了電磁波輻射干擾，更因為沒有了金屬遮蔽裝置，可以降低成本，幫助散熱,使得元件壽命延長，產品生產組裝更加容易。

Abstract
In this thesis, based on Electro-Magnetic theories and principle, we propose a hybrid method to suppress the Electro-Magnetic Interference (EMI) in antenna effect without metal shielding devices. The hybrid proposal uses the suppressing antenna effect rules of EMI technology. Furthermore, the hybrid proposal could meet the EMC requirement; also provide a product cost reduction, better propagation in temperature, and easier fabrication.
In the proposed scheme, we offer a number of methods to reduce EMI radiated emission problems.
1. Grounding (0V reference plane) pattern rebuilding.
2. Using filter and EMI suppressing component technique in the proper positions.
3. PCB layout Modify.
In this thesis, the following contributions are gained:
According to our knowledge, we use hybrid proposal method to lower down EMI radiated emission level without shielding devices from the TFT-LCD Television. We bright out an efficient and economical way to reduce EMI radiated emission level. The experiments show that, we are able to cut off the extra cost, reduce the temperature, and also production easily.

Contents
Abstract (In Chinese) .................................................................................I
Abstract (In English) ...............................................................................VI
Acknowledgement ................................................................................VII
Contents ................................................................................................VIII
List of Figures............................................................................................X
List of Tables.........................................................................................XIII
Chapter 1 Introduction .........................................................................1
1.1 Introduction..............................................................................1
1.2 The Proposed Schemes...........................................................4
1.3 Organization of This Thesis..................................................5
Chapter 2 Overview of Electromagnetic Interference.............................6
2.1 Electromagnetic theory........................................................6
2.2 Theory of Shielding..............................................................11
2.3 Partition and Grounding........................................................15
2.3.1 Partition....................................................................15
2.3.2 Grounding......................................................................15
2.4 Theory of Filter....................................................................19
2.5 EMC Regulations Brief......................................................23
2.5.1 U.S. EMC Requirements...............................................24
2.5.2 European EMC Requirements...................................25
2.5.3 WORLDWIDE EMC Requirements..............................27
Chapter 3 Proposed Methods and Experiment Results.........................28
3.1 Hybrid Proposal of Suppress of EMI Method......................28
3.1.1 Method of Grounding.....................................................28
3.1.2 Method of Filter..............................................................35
3.2 Application to the Example by 19” LCD-TV.........................38
3.2.1 Method of Grounding....................................................38
3.2.2 Method of PCB Layout.................................................39
3.2.3 Method of Filter............................................................43
3.3. EMI Measurement Results.....................................................47
Chapter 4 Conclusions and Future Research...........................................55
References................................................................................................56


List of Figures
Figure 1.1 Diagram of Electromagnetic Radiation..................................2
Figure 1.2 Diagram of Electromagnetic Compatibility...........................4
Figure 2.1 Diagram of Electro-Magnetic Field........................................6
Figure 2.2 Propagation of a plane electromagnetic wave........................7
Figure 2.3 Electromagnetic wave of impedance......................................8
Figure 2.4 Differential mode radiated coupling.....................................10
Figure 2.5 Common mode radiated coupling........................................10
Figure 2.6 Effectiveness of shield attenuation of electromagnetic fields.....................................................................................12
Figure 2.7 Aperture shielding effectiveness..........................................14
Figure 2.8 Diagram of Partition scheme................................................15
Figure 2.9 Single Point Grounding Structure.........................................16
Figure 2.10 Multi-Point Grounding Structure........................................17
Figure 2.11 Filter applications in EMC.................................................19
Figure 2.12 The equivalent and Impedance versus frequency of capacitor..............................................................................20
Figure 2.13 The equivalent and Impedance versus frequency of Inductor ..............................................................................21
Figure 2.14 Ferrite Bead Inductor and equivalent circuit......................22
Figure 2.15 Ferrite Bead Impedance–Frequency Characteristics..........23
Figure 3.1 Diagram of grounding and power supply distribution.........28
Figure 3.2 Diagram of Multi-Ground structure.....................................29
Figure 3.3 E-field coupling between two conductors............................32
Figure 3.4 Diagram of E-field coupling analyzed and equivalent circuit...................................................................................33
Figure 3.5 Diagram of E-field coupling analyzed simplified and equivalent circuit..................................................................34
Figure 3.6 Difference types of signal line filter.....................................35
Figure 3.7 Common-mode choke filter and equal circuit......................36
Figure 3.8 Diagram of Ribbon cable with ferrite clamp........................37
Figure 3.9 Original ground structures in the equipment........................38
Figure 3.10 Add gaskets between metal frame and panel back cover in equipment...........................................................................39
Figure 3.11 Diagram of SD-RAM clock trace on PCB board...............40
Figure 3.12 Diagram of new PCB layout on SD-RAM clock trace....................................................................................41
Figure 3.13 Diagram of real new PCB layout on SD-RAM clock trace....................................................................................41
Figure 3.14 Original PCB layout of partial ground section...................43
Figure 3.15 Modified PCB layout of partial ground section.................43
Figure 3.16 Original PCB layout of partial panel clock section............44
Figure 3.17 Modified PCB layout of partial panel clock section..........45
Figure 3.18 The modify ribbon cable....................................................46
Figure 3.19 Modify the ribbon cable on control cable and I/R cable ..................................................................................46
Figure 3.20a EMI result (vertical) without shielding device.................47
Figure 3.20b EMI result (horizontal) without shielding device.............48
Figure 3.21a Original 19” LCD-TV PCB with shielding device...........48
Figure 3.21b EMI result (vertical) with shielding device......................49
Figure 3.21c EMI result (horizontal) with shielding device..................49
Figure 3.22 EMI results of ground structure rebuild.............................51
Figure 3.23 EMI result with filter and new PCB layout........................52
Figure 3.24a EMI result (Vertical) of final solution..............................53
Figure 3.24b EMI result (Horizontal) of final solution.........................54

List of Tables
Table 2-1 Limits of radiated disturbances at 3 m distance (CISPR13) ............................................................................26

References
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