基於積體被動元件製程之反射式及吸收式共模濾波器設計

Abstract

本論文提出三種以低通濾波器為基礎合成之吸收式以及反射式共模濾波器，用以解決數位訊號系統中的電磁干擾與射頻干擾的問題，共模濾波器在差模傳輸中維持良好的通道效應，而在共模傳輸中提供雜訊的抑制效果。在集總元件合成之濾波器中，差模傳輸之群延遲響應的不平坦會導致訊號的失真，進而影響訊號完整度。本文設計之共模濾波器，在差模傳輸為一低通濾波器，且在通帶內之群延遲響應皆平坦。 本文提出之反射式共模濾波器，以高斯濾波器做為差模響應之設計基礎，在9 GHz 內維持良好的差模傳輸品質，且在2.3到3.1 GHz 內提共模抑制的效果，使用IPD製程的面積大小為0.81×0.78 mm2。吸收式共模濾波器則以兩級電路設計為基礎，第二級電路提供共模抑制，第一級則提供共模阻抗的匹配，將共模雜訊藉由電阻轉換為熱能，並藉由互感來增加差模訊號的通帶。本文提出兩種吸收式共模濾波器，第一種吸收式共模濾波器藉由第一級的匹配電路，來實現全頻帶共模訊號無反射，並在共模抑制頻帶內達到共模吸收的效果，共模雜訊吸收頻帶為4.6-16 GHz，使用IPD製程的面積大小為0.3×0.8 mm2。第二種吸收式共模濾波器則僅僅是在共模傳輸零點的頻率來達成阻抗匹配，可以較有效率的達成共模吸收的效果，共模雜訊吸收頻帶為3.6-16 GHz，使用IPD製程的面積大小為0.38×0.8 mm2。

Three common-mode filters (CMFs) based on low-pass filter are proposed for eliminating electromagnetic interference (EMI) and radio-frequency interference (RFI) in high speed digital system. CMFs transmit differential-mode signals with high quality and suppress the common-mode noise. Filters base on lumped elements have the uneven group delay problem, which caused distortion in high speed transmission and worsen signal integrity (SI). The CMFs proposed in this thesis choose low-pass filters to transmit the differential-mode signal and the group delay is flat in the passband. The 5th order Gaussian to 6-dB low-pass filter design is chosen as the differential-mode equivalent circuit in the reflective type CMF (R-CMF) proposed in this thesis. The common-mode suppression band is from 2.3 GHz to 3.1 GHz and differential-mode 3 dB frequency is 9 GHz. The size of the CMF on integrated passive device (IPD) process is 0.81 × 0.78 mm2. The absorptive type CMFs (A-CMFs) is based on twofold theorem. The second stage is designed for common-mode suppression. The first stage is matching stage. The common-mode energy is converted to heat by the resistor. Mutual inductance is applied to improve the differential-mode response. Two A-CMFs are proposed in this thesis; the first one designed reflectionless response in common-mode, which means the return loss is zero for all frequencies. In the suppression band of the A-CMF, the common-mode energy is absorbed. The common-mode absorption band is from 4.6 GHz to 16 GHz. The size of the CMF on IPD process is 0.3 × 0.8 mm2.The second A-CMF only match the input impedance in the transmission zero of the common-mode response. It is an efficient way to absorb the common-mode noise. The common-mode absorption band is from 3.6 GHz to 16 GHz. The size of the CMF on IPD process is 0.38 × 0.8 mm2.