characteristic impedance of lossy TL

[Eman kamel]

Hi,

i am trying to design a lossy transmission line with characteristic impedance Z0


i choose the RC distributed model


i found that Z0=sqrt(R/wC)
where Rand c are the interconnect resistance and capacitance per unit length.

how i determine the required wire length? and number of RC segments?

please help me
thanks
Eman

 

[Element_115]

Hi,

i am trying to design a lossy transmission line with characteristic impedance Z0


i choose the RC distributed model


i found that Z0=sqrt(R/wC)
where Rand c are the interconnect resistance and capacitance per unit length.

how i determine the required wire length? and number of RC segments?

please help me
thanks
Eman

A "Lossy Transmission line" is a quality of the medium you are using (Coax Cable, FR4, etc.)
The "Per unit length" meas that for some unit of length you medium has some form of
natural "Characteristic impedance" .

You are using Discrete components. They have a value for many frequencies, but as you
go higher in Freq they will change. i.e. a 100 Ohm resistor will be 100 Ohms @ Freq
> ~ 5GHz (for example). but as the λ gets close to 1/4 the size of your resistor the
resistor will act more like a Cap and/or inductor.

You are trying to create the "Representation of the TL Model", with discrete parts.
https://en.wikipedia.org/wiki/Characteristic_impedance

 

[Eman kamel]

many thanks for your reply, i will try to clarify my question, i am using an abstract model for T.L, where the fare and near voltage of the transmission line is Vwin and Vwout, the near and far cureents are Iwin and I rec,
the equations provided are
Vwout= Vwin-Iwin Z0
where Z0 is the characteristic impedance,
Irec= Vwout/Rt
where Rt is termination resistance , matched to the load
when i try to design T.L using this model at 5 Ghz, i am not taking the T.L length into consideration,
i look for T.L equations i found it parameterized per unight length, so my question is , where is the effect of T.L length on current or voltage?

- - - Updated - - -

many thanks for your reply, i will try to clarify my question, i am using an abstract model for T.L, where the fare and near voltage of the transmission line is Vwin and Vwout, the near and far cureents are Iwin and I rec,
the equations provided are
Vwout= Vwin-Iwin Z0
where Z0 is the characteristic impedance,
Irec= Vwout/Rt
where Rt is termination resistance , matched to the load
when i try to design T.L using this model at 5 Ghz, i am not taking the T.L length into consideration,
i look for T.L equations i found it parameterized per unight length, so my question is , where is the effect of T.L length on current or voltage?