運用展頻技術減弱時脈訊號產生電磁干擾之研究

A Study of Reducing Clock Signal of EMI Based on Spread Spectrum

李科論(Ko-Lun Lee)

指導教授 ： 涂世雄

中原大學/工學院/電機工程研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600552

摘要

電子產品的時脈頻率和信號速度的增加使EMI問題更加嚴重，在這篇論文中我們將重點放在展頻減弱時脈訊號產生的電磁干擾。

在我這篇論文中，有幾個主要的重點。第一，我們提出展頻減弱時脈訊號產生的電磁干擾。第二我們利用展頻的基本想法就是對時脈信號的頻率進行微量的調變，使輸出信號的能量盡量平均分散到可控制的小範圍內，降低各諧波在頻譜上相對應的能量峰值。第三，由於每一個諧波的峰值都會受到衰減，因此可有效的降低整個系統所產生電磁干擾。
在這篇論文中，我們將提出以下的貢獻：
(1) 我們可以降低尖鋒能量：因增高的頻率與更快的尖峰速度所導致的能量尖波，都會產生EMI。展頻時脈產生器能緩慢地調整時脈頻率，進而降低尖鋒能量。
(2) 我們可以增加有效的工作時間：為了提昇系統的工作頻率，我們希望時脈訊號的上升時間越短越好，也會使得高頻訊號對其他電路形成EMI，因此使用展頻方法可以解決此問題。
(3) 我們可以減弱電磁干擾：展頻輸出的頻率越高，所呈現各諧波的尖峰能量將會更平均分散，可使產生的EMI大幅降低。
最後，我們可以知道，我們提出的原理可以減弱尖峰能量，並增加有效地工作時間，並減弱電磁干擾。

關鍵字

展頻 ； 電磁干擾

並列摘要

It is the common problem in EMI, coming from the increase of signal speed and clock frequency in electrical products. In this thesis, we focus on the electromagnetic interference from the clocking signal and reduce it by the technique of spread spectrum.

In this thesis has several main focuses. At first we propose the approach of spread spectrum to reduce EMI of clock signal. This approach make its’ energy spread equally to a controllable range, and reduces the corresponding energy of peak of each harmonic wave in spectrum. Finally, the energy of peak of each harmonic wave becomes weaker, we know that this is an effective way to reduce the EMI in all system.
In this thesis, the following contributions are gained：
1. Reducing the energy of peak：Because of the energy of sharp wave, resulting from the increasing frequency and faster speedy of peak, the EMI forms simultaneously. The spread spectrum clock generator, which modulates the frequency of clock slowly, can reduce the energy of sharp wave.
2. Increasing the effective work time：In order to improve the work frequency of system, it is better to have short rising time and high frequency, but also brings EMI. Now, because of the technique of spread spectrum, we can resolve the problem of EMI and have no anxiety to make the high frequency signal.
3. Reducing the electromagnetic interference：The higher output of spread spectrum, the more equal dispersion of energy of peak of each harmonic wave can make, finally, EMI reduces substantially.
Finally, we know that our propose method can reduce the energy of peak, the electromagnetic interference and increase the effective work time.

並列關鍵字

electromagnetic interference ； spread spectrum

參考文獻

〔1〕 Spread Spectrum Timing for Hard Disk Drive Applications,”

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〔7〕 S. Haykin, Communication Systems, John Wiley &Sons, INC., 1994.

〔8〕 F. Lin and D. Y. Chen, “Reduction of Power Supply EMI Emission by Switching Frequency Modulation,” in The VPEC Tenth Annual Power Electronics Seminar, Virginia Power Electronics Center, Blacksburg, Virginia, September 20-22,1992.

〔9〕 K. Hardin and J. Fessler, “An Introduction to Spread Spectrum Clock Generation for EMI Reduction,” Electronic Engineering, vol. 71, issue 867, pp. 75, April 1999.