Friis equation in ADS

[Leiser]

Hi,

I am trying to measure with ADS the noise figure of a 3dB attenuator. I was expecting to see 3dB noise figure but ADS says 0dB. I have also measured the NF of a filter with 3dB of insertion loss but the result is also 0. This components are from ADS library. I am using a S-parameter simulation.

Does anyone know what am I doing wrong?

Thanks.

 

[VEBill]

A general answer to hold you over until someone else replies...

Assuming that the noise floor is set elsewhere (as is often a reasonable assumption), then the loss through an attenuator will dimish the signal and the noise by an equal amount. Thus the noise factor will be zero and the noise figure will be 0dB.

If you have these loss elements before the device that sets the noise floor (before the 1st LNA), then you might have to take the system level impact into account by yourself.

 

[Leiser]

Hi,

I have been able to calculate the NF with the Y-factor in ADS using an Harmonic balance simulation. Using the s-parameters simulation it didn't work.