Talk:Mismatch loss

In order for this article to be really helpful I think it should be more precise:

1)Most of the formulas and statements given only hold true if Z0 is real, which is not generally the case with lossy transimission lines. 2)The formula given under "Mismatch Error" attempts to calculate the Log of a complex number. 3)Mismatch Loss does not generally introduce power losses (reduced efficiency) as stated in the first section; it merely reduces the power delivered to the load (and most of the times the power drained from the source) with respect to the ideally matched situation.

The statement "Mismatch loss represents the amount of power wasted in the system" is correct, but not represented by the equations presented, because the equations do not take into account the resistive losses of the transmission lines, the actual source of the losses. Even with a lossy transmission line, some of the reflected power will be re-reflected to the load, and therefore not wasted. It's my opinion that this article promotes some deeply held myths, and should hold a worthy place in Wikipedia, but should be re-written to present the facts about mismatched losses. — Preceding unsigned comment added by Nojiratz (talk • contribs) 14:01, 15 November 2021 (UTC)

Mismatch loss is an ambigous misnomer

Talk:

The page describes what better is known as "Return Loss". Reflections only occur, where there are waves involved, that are reflected, i.e. meaning returning on a transmission line or waveguide in opposite direction. (Other than using that ambigously confusing misnomer "Mismatch Loss" , the page does make a correct difference, though. It is very valuable. Don't delete it).

So the title should be changed. That includes Links to that title, which unfortunately isn't that easily done. Alternatively, both possible meanings should be described inambigously and a well distinguishing subtitle for each meaning should be used to stop omnipresent confusion.

Reason: Though a transmission line has a characteristic line "Impedance" and can be terminated in a "mismatched" manner, the result on the line is "Return Loss", but should not be synonymed "Impedance Mismatch Loss".

Correctly named "Impedance Mismatch Loss" is caused by terminating a complex impedance source (or a Thévenin equivalent toward the source at a circuit point) with a complex impedance load that is not conjugate complex with respect to the source impedance.

In impedance mismatch there is no reflection involved. Current is unreflected. It only flows through source and load identically and in one way only.

To distinguish these two is necessary, as an old school of teaching claimed that both "in a broader sense" share the same definition equation [1].

That old school of teaching statement was never proven, however. But the contrary can be proven by derivation.

The correct Return Loss equation includes the "Reflection Coefficient" RC, often called Gamma = (Z2 - Z1)/(Z2 + Z1), that is good on Transmission lines. (Their characteristic line impedance by physical limits always is nearly, but not totally, real only. Zo = 50 -j2 Ohms would be realistic, but not Zo = 50 + j100 Ohm)

Impedance mismatch, however, can include any impedances without any limiting nature.

The Impedance Mismatch equation includes the "Impedance Mismatch Coefficient" IMC = (Z2 -Z1*) / (Z2 + Z1) with Z1* meaning conjugate complex of Z1.

To see the misleading result, simply enter in Trevor. S. Bird's definition Z1 = Rs + jXs = 50 + j100 Ohm and Z2 = 100 - j100 Ohm (Resonance compensation of X1 and X2) and see the calculation's result: Negative "Return Loss" (old school equation) in spite of the article's main subject that Return Loss cannot be negative : (false) Return Loss = - 2,76 dB.

If, however, the IMC is used implicitely instead of the implicit reflection coefficient, we get the correct result: Return Loss = + 9,54 dB

("IMC" is not common so far. Please suggest a short and distinguished name instead, if you have a better one. It is not enough to ambigously call both "Gamma".)

Unfortunately even ATIS standardized the "in a broader sense equal" error of that old school of teaching in their glossary for "Reflection Coefficient". [2]

[1] Trevor S. Bird, former IEEE chief editor: „Definition and Misuse of Return Loss“ , IEEE Antennas & Propagation Magazine , Bd.51 , Iss.2, S. 166–167, April 2009.

   The PDF can be found here: https://www.qsl.net/ve2pid/ReturnLossTrevor.pdf

[2] https://glossary.atis.org/glossary/reflection-coefficient-rc/?char=R&page_number=all&sort=ASC — Preceding unsigned comment added by 2001:16B8:2DD3:3300:C9ED:A687:FFC:680D (talk) 11:48, 18 January 2022 (UTC)