S parameters measured by network analyzer

[shahid78]

i am a bit confused on interpreting the scattering parameter results shown by network analyzer

for example the S11 shown by network analyzer for any antenna is in dB.

now if i want to calculate the abosulte values which formula should i use

S11(dB)=20 log ( S11)

or

S11(dB)=10 log (S11)


any help will be highly appreciated

regards

 

[Phytech]

The first one

 

[citizen]

thank you,
i was also have this doubt .

 

[akedar]

well S11 is measuring in terms of power so u have to take 10 log formula

because S=a/b
where a nd b are incident and reflected power waves

u can refer to manual it will further confirm

 

[Slayerza]

I agree since the parameters are measured as power levels it should be the 10log variant. This can easily be derived from the definition of a decibel.

Cheers,
Slayer

 

[loucy]

S-parameter is complex (magnitude and phase) so it cotains more information than the power ratio. In any case, even if you define it as a RATIO of two powers, it doesn't have the unit of power. 10Log is incorrect.

 

[sasaberali]

hi
20×log10×s11=s11(db)