為解決雙倍資料率同步動態隨機存取記憶體系統中信號完整度問題之模型建立

Model Establishment and Deep-Neural-Network Solutions for Signal Integrity in DDR Systems

楊岡昀(Kang-Yun Yang)

指導教授 ： 吳瑞北

國立臺灣大學/電機資訊學院/電信工程學研究所/博士(2018年)

https://doi.org/10.6342/NTU201803785

摘要

雙倍資料率同步動態隨機存取記憶體系統是現在不少電器產品中都會用到的，當訊號達到了十億位元的範圍，許多訊號完整度問題皆會浮現。本論文中，主要會討論三種訊號線結構的訊號完整度問題以及建立其等效電路。首先是單條的有損訊號線，記憶體系統中例如資料線可簡化為這種結構，主要的訊號完整度問題將是損耗。再來是樹狀分支結構，最後是飛躍式結構。
本論文主要結果整理如下，首先先描述有損傳輸線的基礎理論，再來印刷電路板中傳輸線的導體損耗以及介電質損耗將會被近似，於是對應的傳遞函數還有脈衝響應也可以從理論上被推導出來。再來可以利用有理函數去近似傳遞函數，就可以得到傳輸線的等效模型。最後傳輸線的眼圖也會被討論。
再來，將會討論分岔線結構上的震鈴(ringing)現象的背景與發生機制，並建立一個RLC等效模型去描述其性質。最後，利用建立的模型，可以算出分岔線最差眼圖並給出一個最佳化的設計。
訊號線的串音影響也需要被考慮，首先利用之前單條有損傳輸線的模型，可以得到一個推廣的多導線傳輸線模型。再來，利用電容電感的耦合係數，可以建立一個快速的方法得出串音影響最嚴重的導線。這個方法會在一個合作廠商給的實際的例子上演示。
對於太複雜的結構，無法得到一個物理上的等效電路，可以建立一個Matlab自動化設計的流程去做訊號的最佳化，該流程利用Matlab去寫Hspice的電路檔以達到自動的效果。計算了一定的數據之後，還可以利用類神經網路去近似數據，再做最佳化會更快。
當最佳化流程完成了之後，本論文議題出了一個新穎的雙邊飛躍式結構，改進自原本的飛躍式結構。該結構一樣可以用自動化流程去得到最佳解，並用電磁能隙的理論去解釋其物理機制，並且可以最小化能隙並得到最佳化眼圖。

關鍵字

信號完整度 ； 雙倍資料率同步動態隨機存取記憶體 ； 模型建立

並列摘要

The double data rate (DDR) memory system has been widely used in many electronic devices. As its data rate has reached the Gigabit range and many signal integrity (SI) problems arise in the signal lines. In this thesis, SI problems of three kinds of topologies are discussed and its equivalent models are established. First, single-ended lossy transmission line is discussed. Single-ended signal lines such as data lines (DQ) can be simplified into a lossy transmission line. The main SI issue should be the conductor loss and dielectric loss. Second, tree topology is studied. Finally is the fly-by topology.
The research results reported in this thesis are organized as follows. First, the fundamental theory of the lossy transmission line is described. After that, some useful formulas are given for the approximations of both conductive and dielectric losses in PCB-scale transmission lines. The simplified transfer function and thus the corresponding impulse response will be analytically derived as well. Next, by using rational function fitting, the general equivalent circuit can be built for any tx-line parameters. Finally, eye diagram is calculated and the relation to tx-line parameters is discussed.
Next, the research background and the mechanism of the ringing effects on branch line structure are presented. Then, an RLC model is built to characterize the ringing phenomenon. Finally, the built model is used to discuss the worst case eye height of the branch line and a design guide is given to optimize the signal integrity.
The crosstalk noise of interconnects is also taken into account. First, a theoretical method to build an equivalent model similar to the single-ended line is proposed as a generalized version. Next, a fast methodology that predicts the worst-case crosstalk interconnect using coupling coefficient from inductance and capacitance matrices is proposed. Finally, a practical case is demonstrated and some useful design guides are provided to the cooperative company.
For cases that is too complicated to derive a physical equivalent model, an automatic design flows using Matlab to access the optimal design of interconnects is proposed. This flow uses Matlab to write Hspice scripts and run the transient simulation automatically. After some training data are calculated, artificial neural network (ANN) is proposed to find a good fitting function of the optimization design.
After a general optimization flow was developed, a novel dual sided fly-by topology, which is derived from fly-by, is proposed. To facilitate the design, the research utilizes the Matlab automatic flow to acquire optimal design parameters. Conclusively, the electromagnetic bandgap is employed to explain the physical mechanism. The method to minimize the bandgap so as to achieve higher eye height is provided as well.

並列關鍵字

Signal integrity ； DDR ； Modal establishment

參考文獻

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