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

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DazedAndConfuzed

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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.

rfdesign1.JPG

rfdesign2.JPG

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.
 

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?
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.
 

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

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.
 

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