寬頻微波接取技術---子計畫五：微波電路中之電磁干擾抑制研究

Abstract

由於國際電磁相容法規之嚴格執行, 電磁相容問題已經變成電子電機資訊產品是否能 夠輸入國際市場的一個重要因素。過去電磁相容問題多探討於個人電腦等產品主機板 上，然而由於主機板上時脈信號頻率逐漸提昇，此外更因為目前無線接取技術的使用頻 段也從射頻逐漸移往微波，因此發展微波頻段之電磁干擾防制技術已是刻不容緩的事。 本子計畫預期將配合總計畫，發展微波電路之電磁干擾防制技術，具體而言，本子計畫 將探討多層印刷電路板結構之電磁干擾源及信號完整性分析。 在第一年中我們為了解決印刷式傳輸線在微波頻段因長度過長而引起之電磁輻射問 題，而開發以緩波結構為基礎之印刷式傳輸線；由於緩波結構之傳波常數較自由空間中 平面波之傳播常數大，因此能量將集中於介質基板中而不致於輻射，因而可以大幅解決 不必要之電磁輻射問題。在第二年中，我們將研究緩波結構之電磁輻射問題，由於緩波 結構大多為週期結構，因此在極高頻操作時，會有漏波現象，產生天線輻射效應。除了 輻射物理機制之探討外，我們也將考慮實際情況，對於多線同時饋入產生之陣列天線方 向性輻射問題作理論及實務上之研究。在第三年中，我們將探討多層板結構中，接地面 與電源面之間，由於多個主動元件同時開關所造成之地彈雜訊現象，同時利用電磁晶體 結構操作在禁波帶來抑制雜訊之傳播，避免在產品無法通過電磁相容測試時盲目地增加 去耦合電容及電感來降低干擾，以求治本而非治標。本子計畫與其他子計畫有極為密切 之合作關係，例如將可配合子計畫一研發新形式印刷式寬頻天線之微帶線結構，利用緩 波微帶線來取代傳統之微帶線，進一步可以作為子計畫二設計縮小化寬頻耦合器及濾波 器之用。除此之外，更可以提供計畫三晶片內縮小型連接線之設計概念。此外，子計畫 四所發展之適應性時域有限差分法更可以用來驗證本計畫之理論分析及實驗結果。

In the past 10 years, most of the electromagnetic compatibility problem focused on the motherboard of personal computer. Due to the increasing clock rate of modern CPU, the electromagnetic radiation frequency increases from several hundred MHz to several GHz. Moreover, the mobile wireless communication system gradually increases its operation frequency up to microwave frequency. For example, the 「M-Taiwan」proposal would let everyone to access the internet everywhere in Taiwan using the protocol of IEEE802.16/IEEE 802.11. Since the allocated frequency of IEEE 802.16 covers from radio frequency to microwave, we could expect that the personal microwave transceiver system will be popular in the near future. Nevertheless, the (EMI and EMS)) electromagnetic interference and susceptibility problem in microwave frequency was rarely touched before. In the preset, the EMI problem can be resolved using passive components, such as decoupling capacitors or ferrite beads, for the low-frequency operation circuit. However, since the passive components have considerably parasitic effects in microwave frequency, the EMI debug technology will be no longer valid for resolving the microwave EMI problem. We have to resort to the circuit design and layout problem invoking the knowledge of electromagnetism. This sub-proposal joints the main proposal to investigate the electromagnetic interference phenomena and signal integrity problem in microwave circuit design. In the first year, we will devote ourselves to the study of slow-wave-based printed transmission line design. Since the slow wave has the propagation constant greater than the free space wave number, the electromagnetic field will be concentrated in the substrate with radiating. This will further reduce the possibility of electromagnetic radiation and coupling effect. We will calculate the dispersion characteristics of the slow-wave-based transmission line using mode-matching method, and the signal integrity will also be investigated. In the second year, we will treat the radiation characteristics of the slow-wave based transmission line; in particular for the case of multiple lines. Since the slow-wave structure usually is a periodic structure, the wave leakage from the higher space harmonics would be a problem causing EMI. Therefore, the leaky wave phenomena of a periodic printed waveguide structure like the slow-wave-based transmission line will be the topic of research in this year. Besides, the array antenna effect due to the traces placed in parallel is also the key issue to be investigated. In the third year, the research topic will be concentrated on the EMI source caused by the (SSN) simultaneously switching noise. The SSN is resulted from the switching of the active devices at the same time. The fluctuation of the voltage level at the ground- and power- plane will degrade the signal integrity of the overall circuit system. To suppress the SSN, we would employ the electromagnetic crystal (or electromagnetic band-gap structure) and operate it in the stop-band region. This method has been reported in the literature to eliminate the SSN in discrete and narrow bandwidth; however, the broadband suppression and miniature periodic is still the 「Holy Grail」to be found. This sub-proposal has a tight connection with the other ones. To mention a few, the slow-wave-based printed transmission line could be employed in the design of broadband antenna, broadband coupler and filter in sub-proposal I and II. The concept of design can also be adapted in the IC level micro-strip line realization. The ADI-FDTD method developed in the sub-proposal IV can be used to verify the numerical and experimental results obtained in this proposal.