Step-wise change in level of signal/noise in R&S spectrum analyzer

[noori.re]

Hello every one,

I use an specturm analyzer of R&S. in the spectrum at 5 GHz and 8 GHz I see in change in level of Noise/signal like a step. I checked the trancducer settings. it is not related to the trnacducer settings.
Does someone know how can I reslove this?
Strat freq: 2 GHz
Stop freq: 12 GHz
Res BW: 1MHz

 

[D.A.(Tony)Stewart]

So what is the cause? measurement? setup? sensor? s11? s21? s22?

 

[G4BCH]

Give more information, model number and a screen shot of the display.
It is likely that it is the analyser changing IF gain to compensate for the change in gain when the mixer input frequency range changes. this keeps the reference level constant, but changes the noise floor. This range switching behaviour is very common.

 

[noori.re]

It is an FSW26
You can see 2 jumps. one in 5 GHz. the othe in 8 GHz. Trnamitter is off still the jump is there. even if I diable the trancducer, the jumps are there.

 

[G4BCH]

It is a range changing artifact, to cover such a wide frequency range the analyser has to change the local oscillator and possibly use harmonic mixing. The IF gain needs to be increased to compensate for increased loss so that the reference level remains constant. It is nothing to worry about. The sudden change at exactly a 1GHz multiple is a give away.