[SI-LIST] Re: Transmission Line calculator Problem!

1.Transmission line calculators use empiric formulae, so they are just 
estimates.
2. Check if the default dielectric constant for FR4 is slightly different in 
these tools.

/Mikhail


----- Original Message ----- 
From: "Mohamad Haghtalab" <mohaghtalab@xxxxxxxxx>
To: <SI-LIST@xxxxxxxxxxxxx>
Sent: Sunday, March 15, 2009 10:35 AM
Subject: [SI-LIST] Transmission Line calculator Problem!


> Hi all
> ═
> I want to design diff Lines for carrying═LVDS Signals(pulses with 100MHz 
> and rise time of <1 ns) in form of Stripline and MicroStrip,but I have 
> problem with calculating exactly their characteristic Impedance.
> In═both HyperLynx(from mentor) and═Cadence Allegro(V16.2) (Transmission 
> Line Calculator) I tryed to calculate this,but what I obtained in both is 
> different with each other
> ═
> I want to achieve 100 ohm for Zdiff, I derived (from formula and 
> constraints)═ :
> ═══════════════════════════════════════════════════════════════ Stripline 
> :═ W=5 mil══ S=5 mil═══ h$mil
> ════════════════════════════════════════════════════════════════microstrip:═ 
> W mil══S=5 mil══ h═mil
> ══════════════════════════════════════════════════════════════════════════ 
> dielectric : FR4
> ════════════════════════════════════════════════════════════════════ 
> copper thickness : 1.4 mil
> ═
> for Stripline
> ═
> HyperLynx : 85.5 ohm
> Allegro══════: 74.34 ohm
> ═
> for══microstrip
> ═
> HyperLynx═ :97 ohm
> Allegro══════ : 92.37 ohm
> ═
> so What Should I do ? (for exactly calculating Z0)═
> ═
> Thanks for Help
> ═
> Best Regards
> ═

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