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博碩士論文 etd-0725107-171301 詳細資訊
Title page for etd-0725107-171301
論文名稱
Title
利用展頻技術抑制時脈電路的電磁干擾
Suppression of Electromagnetic Interference for a Clock circuit by Using the Spread Spectrum Technique
系所名稱
Department
畢業學年期
Year, semester
語文別
Language
學位類別
Degree
頁數
Number of pages
54
研究生
Author
指導教授
Advisor
召集委員
Convenor
口試委員
Advisory Committee
口試日期
Date of Exam
2007-07-05
繳交日期
Date of Submission
2007-07-25
關鍵字
Keywords
展頻時脈產生器、電磁干擾、展頻、時脈電路
Electromagnetic Interference, Spread Spectrum, Clock Circuit, Spread Spectrum Clock Generator
統計
Statistics
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中文摘要
隨著系統時脈的提升,時脈電路(clock circuit)將會造成大量的電磁干擾(EMI, Electromagnetic Interference),為了降低產品的電磁干擾,各種EMI對策被發展出來。本論文是研究展頻(spread spectrum)技術抑制時脈電路的電磁干擾,此技術是針對時脈電路產生的訊號做微量調整,使輸出的能量分散於可控制範圍內,降低各諧波在頻譜上的峰值能量,使得產品較容易通過電磁相容測試。我們由理論推導,推得展頻EMI衰減量(attenuation)的因素,分別為調變指數(modulation index)與調變波形(modulation profiles),藉由數值分析軟體驗證展頻抑制EMI的效果,並提出衰減量公式讓設計者可控制各頻率點的衰減值。實驗部分,採用市售的展頻時脈產生器,驗證展頻技術抑制EMI的效果。時脈電路以梯形波訊號較具代表性,此訊號包含上昇時間(rise time)與工作週期(duty cycle),探討改變上昇時間與工作週期對展頻的影響。高速時脈電路,較短的上昇時間會產生高次諧波(harmonic)的問題,經模擬與實驗驗證,展頻技術具有抑制高次諧波的特性,且每個諧波都會受到抑制,對整個系統的EMI,有大幅度的抑制效果。
Abstract
With the increasing system clock, a clock circuit will cause an amount of electromagnetic interference. To reduce EMI of the products, various EMI strategies have been developed. In the thesis, we study the suppression of electromagnetic interference of a clock circuit by using the spread spectrum technique. The basic idea of the spread spectrum is to slightly modulate the frequency of the clock signal and the energy of the signal will be dispersed to a controllable range to reduce the peak energy of each harmonic wave in the spectrum, and the products can pass the electromagnetic compatibility test more easily. We obtain the attenuation factor of spread spectrum from the theoretical derivation, including modulation index and modulation profiles. From the numerical simulation, we verify that spread spectrum technique can suppress the peak energy. We propose the attenuation formulas which can control the attenuation of every frequency point. To verify our findings, we use a spread spectrum clock generator from market to perform measurement. The trapezoidal waveform can be used to represent a clock circuit. Its waveform includes rise time and duty cycle. We will discuss the influence of rise time and duty cycle on the spread spectrum technique. Shorter rise time will cause high order harmonics in the high speed clock circuit. We verify that spread spectrum technique can suppress high order harmonics from both the simulation and experiment. Because every harmonic can be suppressed, the spread spectrum technique has the good suppression effect for the whole system.
目次 Table of Contents
誌謝 i
中文摘要 iii
英文摘要 iv
目錄 v
圖表目錄 vii

第一章 序論 1
1.1 研究背景 1
1.2 論文的編排方式 3
第二章 展頻技術的理論基礎 4
2.1 展頻技術的原理 4
2.2 Carson’s rule 8
第三章 展頻EMI衰減量的因素 10
3.1 展頻抑制EMI的數值模擬 10
3.2 三角波調變訊號 16
3.3 指數波調變訊號 18
3.4 輸入調變訊號與輸出頻譜形狀的關聯性 20
3.5 考慮諧波數的EMI衰減量公式 21
第四章 實驗結果與討論 23
4.1 展頻時脈產生器的介紹 25
4.2 量測配置 26
4.3 近場探棒的介紹 27
4.4 展頻時脈產生器抑制EMI的實驗 27
4.5 上昇時間與工作週期的影響 33
第五章 結論 39
參考文獻 40
參考文獻 References
[1] V. H. Kee, “EMI Compliance by Design”, http://www.ultratech-labs.com, October 2001.
[2] F. Lin and D. Y. Chen, “Reduction of power supply EMI emission by switching frequency modulation,” IEEE Trans. Power Electron., vol. 9, no. 1, pp. 132-137, 1994.
[3] K. Hardin, J. Fessler, and D. Bush, “Spread spectrum clock generation for the reduction of radiated emissions,” in Proc. IEEE Int. Symp. Electromagn. Compat., 1994, pp 227-231.
[4] H. H. Chang, I. H. Hua, and S. I. Liu, “A spread-spectrum clock generator with triangular modulation,” IEEE J. Solid-State Circuit, vol. 38, pp. 673-676, April 2003.
[5] W. T. Chen, J. C. Hsu, and C. C. Su, “A spread spectrum clock generator for SATA-II,” in Proc. IEEE Int. Symp. Circuits and Systems, 2005, pp. 2643-2646.
[6] S. F. Ho and H. Y. Huang, “A wideband programmable spread-spectrum clock generator,” in Proc. Asian Solid-State Circuits Conf., pp. 521-524, Oct. 2005.
[7] S. Haykin, Communication Systems, 3rd ed., Hoboken, NJ:John Wiley & Sons, Inc., 1994.
[8] G. Kennedy, Electronic Communication System, McGraw-Hill, 1984.
[9] A. V. Oppenhem, A. S. Willsky, Signals & Systems, Prentice Hall, 1997.
[10] J. Kim, P. Jun, J. Kim, “Dithered timing spread spectrum clock generation for reduction of electromagnetic radiated emission from high-speed digital system,” in Proc. IEEE Int. Symp. Electromagn. Compat., 2002, pp 413-418.
[11] A. Santolaria, J. Balcells, D. Gonzalez, J. Gago, and S. D. Gil, “EMI reduction in switched power converters by means of spread spectrum modulation techniques,” Power Electronics Specialists Conference, 2004. PESC 04. 2004 IEEE 35th Annual, vol. 1, pp. 292 – 296, June 2004.
[12] CY25811 A Spread Spectrum Clock Generator, Cypress Semiconductor Corp., San Jose, CA, 2004.
[13] I. Young, J. K. Greason, and K. L. Wong, “A PLL clock generator with 5 to 110-MHz of clock range for microprocessors,” IEEE J. Solid-State Circuits, vol.27, pp. 1599-1607, Mar. 1992.
[14] Agilent HP 11940A Close Field Probe, Agilent Technologies Inc. [Online]. Available: http://www.agilent.com
[15] 花怡慧,66-133-266 MHz展頻時脈產生器之設計與製作,國立台灣大學電機工程所碩士論文,2002。
[16] C. R. Paul, Introduction to Electromagnetic Compatibility, John Wiley & Sons, Inc., 1992.
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