[SOLVED] Help with mismatched circuit

[LandLack]

Hi, I've simulated a mismatched circuit: trace characteristic impedance=67.5 ohm, while all the devices have 50 ohms; and there are in total 6 devices in a row. The circuit has signals up to 1.4GHz.
The results were the same as with the circuit with traces' characteristic impedance of 50 ohm. How is this possible? I thought that I wold have some some losses due to the reflecting coefficient: R=(67-50)/(67+50), where R is the reflected voltage (and this is to be repeated by all 6 of the devices).
How is this possible? Am I forgetting something?
Please help understand this thing...

Best Regards,
LandLack

 

[FvM]

Matching at both line ends and electrical length has to be considered.What's the actual circuit?

 

[Ow@i$]

going from 50 ohm to 75 ohm system will give a VSWR=1.5:1 (acceptable) , and about 4% of power will be lost due to this mismatch of (25 ohm) ..
u can do all the calculation using basic formulas...
the point is it is so low 0.04 (4%) part of the incident power that it becomes un measurable... in your case the difference is more low 17.5 ohm...
so i suggest for understanding the mismatch try increase the impedance of the trace so the result becomes more obvious...
if it didn't work too than u must be missing something else that needs to be bugged out!!!
Cheers

 

[peol]

Maybe the line lengths between the components are quite short? In that case the line impedance mismatch will not have a major impact.

 

[FvM]

More generally, connection of a 50 ohm source and load by a line of different impedance won't be described by a single real reflection coefficient as considered in post #1 and #3. Instead you get a complex reflection coefficient as function of the line length. It will be zero for length of n*λ/2 and maximal for λ/4, 3*λ/4, ...