Eyebrow Corner

高速介面的相位偏移規格 總結幾個目前常用並且明文規定的高速介面的相位偏移規格： 單位間隔（Unit Interval, UI）是數據傳輸中的一個基本單位時間，用來表示信號在傳輸過程中的每個比特或符號的時間長度。它是高速串行接口設計中的關鍵參數，用於計算抖動、偏移（skew）等時間參數。UI 的計算方法如下：  Unit Interval (UI) UI 是每個比特或符號的時間間隔，其計算方法是數據速率的倒數。 公式： UI  =  1 /  數據速率 ​ 數據速率通常以 Giga Transfers per second (GT/s) 或 Giga Baud (GBd) 表示，這些單位代表每秒傳輸的比特或符號的數量。 Skew Spec. of High Speed Interfaces Summarize the skew specifications of several currently commonly used and clearly specified high-speed interfaces: The Unit Interval (UI) is a fundamental unit of time in data transmission, used to represent the duration of each bit or symbol during signal transmission. It is a crucial parameter in the design of high-speed serial interfaces, used for calculating jitter, skew, and other timing parameters. The calculation method for UI is as follows:  (UI) UI is the time interval for each bit or symbol, calculated as the reciprocal of the data rate. Formula: UI  =  1 /  Data Rate ​ The data rate is typi...

Skin effect on signal integrity   As the signal transmission speed becomes higher and higher, the operating frequency becomes higher and higher, and the current tends to flow more and more on the surface. The relationship between the operating frequency and the skin depth is as follows: The following is a comparison table of frequencies and skin depths of copper commonly used in current high-speed products: In terms of PCB design, it is usually necessary to reduce the roughness of the copper surface due to signal integrity considerations. However, if the roughness is too low, the bonding force between copper and P.P. of the PCB will be insufficient, thus affecting its reliability. 趨膚效應對訊號完整性的影響 由於訊號傳輸時速度愈高，操作頻率就愈高，而電流就會愈趨向導體表面流動，其中操作頻率與趨膚深度的關係如下： 以下列舉一些目前高速產品常用的頻率與銅材質趨膚深度的對照表： 以PCB設計而言，通常因為訊號完整性考量需要降低銅表面的粗糙度，但是粗糙度太低也會造成PCB的銅與P.P.結合力不足，進而影響其可靠度。

談玻纖編織效應如何影響訊號完整性 近年來，由於AI應用的發展，高速訊號差分走線的應用頻率愈來愈高，對於訊號完整性的要求也愈來愈大，因為走線不等長、參考層不對稱等因素造成的skew（訊號延遲）對誤碼率（Bit Error Rate）的影響也愈來愈大，本章即是探討由玻纖編織效應造成的訊號延遲所造成的影響及可能的解決方式。 由於skew造成的相位延遲 skew造成的Insertion Loss Insertion Loss的共振點可由上述公式算出，也就是說，共振頻率與玻纖、樹脂之介電常數（Dk）以及走線經過的玻纖長度有關。 以下列舉幾個常見的解決方法： 1. 差動對以Zig-Zag形式走在玻纖上。 2. 將玻纖與走線的相對角度旋轉7至10度。 3. 選用經向與緯向有相同玻紗數的玻纖布。 4. 選用與樹脂相近Dk的玻纖布。 Zig-Zag形式走線 How Fiber Weave Effect Affects Signal Integrity Recently, due to the development of AI applications, the application frequency of high-speed differential signals have become higher and higher, and the requirements for signal integrity have also increased. Due to skew caused by factors such as lengths mismatch of traces and asymmetry of the reference layers, it has the increasing impact on the bit error rate of the entire system. This chapter discusses the impact of signal delay caused by the fiberglass weave effect and the corresponding possible solutions. Phase delay due to skew Insertion Loss due to skew The resonan...