以低溫共燒陶瓷製程設計超精緻縮小化高速差模訊號之共模濾波器

Abstract

本論文提出一種新型的SMD (Surface-Mount Device) 形式共模濾波器及其縮小化設計，此共模濾波器是利用在單一蘑菇狀結構(Mushroom Structure)於低溫共燒陶瓷技術(Low Temperature Co-fire Ceramic)，並於此結構中左右對稱設置訊號線，使對共模訊號和奇模訊號產生不一樣的效應：對差模訊號，回流電流不通過此結構；而對共模訊號其回流電流則通過此結構。由於此結構分別對差模和共模訊號產生不同效應，而使得共模雜訊得到抑制，而差模訊號得以通過。經過設計此結構的物理參數，可以得到相應的不同效果。 由於其縮小化形式，這種共模濾波器可以直接應用表面嵌置技術(Surface-mount technology)，外接在印刷電路版上。不同於傳統共模扼流圈（Common-mode choke），此共模濾波器具有寬頻抑制的效果，而且在微波頻段中，差模訊號依然保持良好完整度。 本文將針對利用此蘑菇狀結構下的不同架構、物理參數與特性變化作分析，並建立出等效電路模型與實驗結果比較。此外，在頻域分析中，此共模濾波器達到了100％以上的寬頻抑制效果；而在時域分析中，此共模濾波器對共模雜訊的抑制效果達到60%以上。更重要的是，在抑制共模訊號的同時，差模訊號的完整度和傳輸品質幾乎沒有受到影響。

Compact SMD-typed common-mode filters applying single mushroom structure is proposed and miniaturized in this thesis. This type of filters is realized in LTCC technology and can be mounted on PCB using surface-mount technology (SMT). By routing the signal traces symmetrically, different effects are produced to common mode and differential mode. For common mode signal, the return current go through the mushroom structure, while the odd mode return current is zero at the via. By designing the physical parameters, the desired performance can be achieved. The SMD-typed filters are unlike the conventional common-mode choke. The filter has wide-band common-mode suppression and good differential signal integrity at GHz frequency range. In this thesis, it is focused on the design, analysis and investigation of the effect on differential physical configuration of the structure. The common mode suppression of the filters with fractional bandwidth larger than 100% is achieved in frequency domain. In time domain, the filters produce over 60% reductions in common-mode noise voltage. More importantly, very little influence is seen for differential signal; hence, the high-quality signal integrity is maintained.