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Mar 27th, 2023, 1:02am
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 Basic question on transmission line (Read 325 times)
 vlsi_design Junior Member Offline Posts: 20 Basic question on transmission line Mar 29th, 2022, 7:11am   Hi,T lines no matter how long they are, if properly terminated with ZL=Z0=R, always presents a resistive load and no capacitive load. Instead if I use a long trace of line of comparable dimension I get a huge capacitor with the substrate (say). Is there an intuitive way to understand this? or the best way is to rely on theoretical formula of Zin = f(Z0,ZL,tan(beta*l)) where once we substitute Z0=ZL, we see pure resistive input impedance?How the huge cap magically disappears? Back to top IP Logged
 Horror Vacui Senior Member Offline Posts: 125 Dresden, Germany Re: Basic question on transmission line Reply #1 - Jul 26th, 2022, 4:43am   Aren't you looking at low frequencies? What is the electrical length of the structure? At DC every t-line is a cap. (beta has a frequency dependence: at f=0 beta goes to 0. I prefer the substitution: beta*l=2*pi*{electrical length}, because it makes things in the argument of the tangent easier to grasp) Back to top IP Logged
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