differential stripline impedance calculate

Differential Stripline

Impedance Calculate

Using 3 Simulation Toolkit

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Jay Chang

按照板廠提供的數據, L4 ref L3/L5算出來的impedance = 77.5 Ω

http://www.multek.se/engelska/engineering/pcb-structures-

2/differential-stripline-impedance-calculator-2 2

Use one of the most popular simulation tool Saturn_PCB_Toolkit_V7.02

按照板廠提供的數據, L4 ref L3/L5算出來的impedance = 77.51 Ω

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Use one of the most popular simulation tool Polar Si9000

按照板廠提供的數據, L4 ref L3/L5算出來的impedance = 81.32 Ω

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既然都用Polar惹, 那就算一下 freq dependent behavior

Z0 vs freq

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和total loss vs freq

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Why Polar Si9000跟前兩個算出來的很接近但不太一樣

因為Polar 是EM field solver (field solver condition代對�就是準!!)

field solver分兩大類1. Differential Maxwell equations�電磁場所在的整個域的離散化(網格化)�解稀疏線性

matrix

代表的有FD(有限差分), FEM(有限元素 HFSS為代表)…

2. integral equation methods�對電磁場的源(通常是電荷密度)進行離散化�解Green function

代表的有BEM(邊界元素 Polar為代表)…

結論:

a. QTI算的impedance應該有問題, lossless又是freq independent阻抗應該沒那麼大, initial

value不知道有沒有代對也不知道用甚麼算的(猜是SIWAVE or ADS ?)

b. 那time skew FAIL應該就是differential line不等長的關係

先降~

To be continued…

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Single-ended Microstrip

Impedance Calculate Using

ADS

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• ADS用優化的辦法來求出阻抗• 先用一個簡單的Microstrip來驗證ADS and Polar的結果是否吻合, 再回到我們與QTI的simulation

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Our Qlink Case

Impedance Calculate Using

ADS Optimization

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Our Qlink Case

Impedance Calculate Using

ADS EM Model

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Differential Line Analysis

Using ADS

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v1: excited voltage與反射電壓的疊加v2: output端電壓

v3: near end crosstalk (NEXT)

v4: far end crosstalk (FEXT)

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Diff mode excitation Comm mode excitation

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TDR Analysis Using ADS

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