Actually some research papers have written Returnloss(dB) and some others have written S11(dB). Couple months back I had seen there was an article in IEEE which has given the clarification. If any one have any information kindly tell me.
Hello Sounik,
Further to the explanation provided by Milo, I would like to simplify as the S11 parameter is primarily measured by a VNA and deals with the Power ratios as stated by Milo. The Return Loss on the other hand deals usually with the voltages and is used in the VSWR measurements, either manually or through the instrumentation.
I hope this adds to the knowledge of the answer you are seeking for.
Best Luck!
Thank Prasanna Waichal and Milo Hyde for your clarification. Have you got the IEEE papers which has clarified this.
Hi Sounik
Please read
https://en.wikipedia.org/wiki/Scattering_parameters
The relation between S11 and RL is given
Definitions for both are given as well
Best Regards
Xavier
The scattering parameters are measured and defined for two port circuits with excitation from a source with the characteristic impudence Z0 and terminated with Z0.
The return loss do not impose such condition during its measurements. So, S11 is a special case of the return loss.
In Microwave engineering, they are basically the same thing but opposite sign. S11 will be negative in dB, but since the Return Loss is a loss, it is expressed positive in dB.
Thank You Xavier Le Polozec, Abdelhalim Zekry, Sandra Cruz-Pol for your suggestive answers.
Return loss( RL) is the variation in dB between the power incident on the load and the power reflected back to the source expressed in db and always positive for passive antenna under test expressed mathematically as;
RL= 10log10 (P incident/P reflected) and the minor difference with reflection coefficient is that return loss is the negative of reflection coefficient also expressed in decibel.Therefore RL= -20log10 multiply by the magnitude of the reflection coefficient.
return loss is without the negative sign as the term loss indicates -ive sign already
while
S11 has the negative sign
S11 is scattering parameter and it is given as S11=10log(Pr/Pi), while return loss is given as RL=10log(Pi/Pr). So, we can say that S11=-RL
Return loss and S11 both presents reflected power with respective to incident power. However, the reflection coefficient (S11) is negative quantity and return loss is positive quantity.....
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