Attenuator S parameters
Attenuator S parameters
(OP)
Hello All,
Excuse me for asking what probably is a question with an obvious answer, but if an attenuator's S21 parameter is smooth for a given bandwidth, should the S11 parameter also be smooth for that bandwidth? I would think yes, but my measurements seem to indicate otherwise.
Excuse me for asking what probably is a question with an obvious answer, but if an attenuator's S21 parameter is smooth for a given bandwidth, should the S11 parameter also be smooth for that bandwidth? I would think yes, but my measurements seem to indicate otherwise.
RE: Attenuator S parameters
RE: Attenuator S parameters
An example: network analyzer with 0 dBm (1 mW) output and measuring a 3 dB pad. S21 is -3 dB and the received power is 0.5 mW. S11, for example may jump between -20 and -30 dB which looks large (10 dB jumps), however S11 is only jumping in this case between 0.01 mW and 0.001 mW. S21 may be varying by 0.01 mW and still look very flat in dB.
So it is possible that your S21 measurement is varying as much in terms of linear power as your S11 measurement, but because of the log scale it may not appear to be varying as much.
Peter
RE: Attenuator S parameters
RE: Attenuator S parameters
If you had a nearly lossless part (air dielectric adapter, with one support wheet of course), your S11 "VSWR plot" would look smooth and close to 1:1 while your S21 loss would look smooth. So you can get smoothness on both if you plot S11 VSWR and S21, but not if you plot S11 rtn loss.
Most items have multiple dips in the S11 rtn loss across the operating band.
kch