Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Signal Wavelength vs Transmission Line Length

Status
Not open for further replies.

celebrevida

Member level 2
Joined
Oct 25, 2016
Messages
47
Helped
0
Reputation
0
Reaction score
2
Trophy points
8
Activity points
524
I've read that a rule of thumb is:
T-line length >= 0.1 Signal Wavelength

you need to consider transmission line effects. But if the T-line is "shorter", T-line effects can be ignored.

But regardless of length, if Zo =/= Zl wouldn't issues of reflection and impedance matching still apply?

Why can T-line effects be ignored when it is "short"?
 

It depends on order of mismatch. If you put 1000 Ohm 0.1λ it must be considered, because effect is very significant. For such huge mismatch effect vanishes around 0.001λ.
 

Hi,

Why can T-line effects be ignored when it is "short"?
As already said:
* the effects will be there

But the effects on signal amplitude will be less and the effects in time will be shorter. Thus it's more likely they will not harm.

Klaus
 

The 1/10 lambda rules means, you can analyze transmission lines as lumped circuit (series L, shunt C) below this length without causing large errors. But the lumped elements must be still considered, their effect can be very small or large, depending on the impedance relations.

If you are in an impedance matched design, it may be easier to use transmission line calculation methods even for short lines.
 

A load Zl is seen different when it is looked through a tl. There is a famous formula saying zin= zo*(zload+jz0*tan(teta))...
As you can observe, if teta is small enough(the line short enough), zin becomes zload. When the line length increases, the load start to be seen different.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top