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Differential co-planar lines and results

Question asked by mukulratwani on Jul 12, 2014
Latest reply on Aug 6, 2014 by volker_muehlhaus
Hi all, 
         I am doing S-parameter simulation of differential co-planar lines(with ground plane). Specification of my simulations are as follows: 

Er = 3.66
Thickness of PCB   = 0.13 mm
Trace thickness = 1.4 mil
W = 38 um
G = 50 um
S = 50 um

Ze = 114 (even mode impedance)
Z0 = 50 (Odd mode impedance)
Zo = 76 (Characteristic impedance)

I am using ADS linecalc to calculate width and spacing. After making layout I am defining four ports P1, P2, P3, P4 where P1 & P2 on one side and P3 & P4 on the other side(Picture attached  in Fig1). I am simulating it for frequency range 1Ghz to 60 Ghz. After getting S- Parameter from this layout, I am saving it as S4P file. Using this file in ADS schematic and applying differential port of 100 ohm (both side)(Picture attached in Fig3). But from this I am not getting good results i.e not getting good S11 or not achieving proper matching.(Result attached in Fig4). 

Does my testing method of Differential Co-planar line is correct.  ? 

If it is not so please give some suggestion to correct it or give some another testing method.  

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