Help simulating RF cascade with linear and non-linear components in ADS

Hello,

I am currently trying to simulate an RF cascade in ADS comprising of two similar LNA's, a fixed attenuator, a digital (programmable) attenuator and a 60 degree/GHz phase shifter. This cascade is to be simulated at 2, 3 and 4 GHz respectively (varying Pin from -10 dBm to 10 dBm) and at each frequency the input TOI, output TOI, system gain and output power of the system are to be determined using ADS. I have included a schematic of the cascade as well as the characteristics of the LNA's. My biggest issue is when I try to run a simple Harmonic Balance (HB) simulation and attempt to plot something as simple as vout (dBm) vs frequency I end up with invalid vout readings.

I had tried to run a Budget type sim but I learned you cannot use the linear components in that sim as I do not know their S-parameters (do they have associated S-paramters?).

Any help at all in terms of creating a meaningful output for the mentioned parameters would be greatly appreciated.





Adam B

Since you use small signal s-parameters HB analysis will not give you an logical result.
You should do simply s-parameters analysis.That's it.. Because there is no nonlinear element in your circuit.

I am a little confused when you say there are no non-linear devices, are the RF amplifiers not considered non-linear in this case?Also if I were to conduct an S-Parameter analysis in ADS, how can I use the simulation to determine the input and output TOI?

S-parameters are always linear.

From what I understand, the ADS model that you used can define nonlinear parameters like compression for some system level simulation, but I doubt if that is applicable for HB simulation. I would expect that HB uses the exact (linear) S-parameters from the top of the parameter list.

DazedAndConfuzed said:

I am a little confused when you say there are no non-linear devices, are the RF amplifiers not considered non-linear in this case?Also if I were to conduct an S-Parameter analysis in ADS, how can I use the simulation to determine the input and output TOI?

Click to expand...

Can you see any nonlinear component in your circuit ?? Since there isn't nonlinear elements, there is not neither non-linearity so analyzing TOI is impossible within this setup.
The components/elements which are represented by s-parameters are always Linear and they do not produce any non-linearity at all.You have to find either the amplifiers itself defined by nonlinear elements ( active and possible passive elements ) or X-parameters measured by VNA.. Otherwise there is no sense to simulate this circuit to achieve TOI or other non-linearity metrics.

BigBoss said:

Can you see any nonlinear component in your circuit ?? Since there isn't nonlinear elements

Click to expand...

What might be confusing here: This AMP element from the System Models palette has nonlinear SOI/TOI and compression parameters, but I think that is for system simulation only, and for HB circuit simulation it is a linear device with the given S-params.