How to use an FET model in ADS

Hello,

I used a GaAs FET model pf_mit_MGF2430A_19931015 offered by ADS library to design a Ku band PA. It's OK when I did DC simulation. But when I do small singal S parameter simulation, the gain is much smaller than the gain using S2P file model. (the DC power has been added properly, namely, Vd=10V/Vg=-1.0V and a fan-type structure has been used for HF isolation.)
I just wonder whether this model can be used for S parameter simulation, and how to do it. Thank you very much!

The s-parameter from the model will never be eaxcly same as the measured s-parameter. I have tried it many times. Even the FET is from agilent.

Thank you! But why? And I still confused because with different model but the same biasing the gain difference could be 10dB! Thanks again.

Hi,
Are you using a properly DC feed in your simulations?
(high impedance for DC and a block capacitor to the RF source. In your simulations use ideals elements. In ADS Lumped-Components DCFeed and DCBlock)

Are you using in your simulated circuit 50 ohm source and load impedance?

Did you check in the specs at what temperature the measured was made it?

Regards,

There two types of S-Parameter sets.With packaging effects are included, and not included. Probably the s-parameters in the library (in general) don't include parasitic elements of the case and there fore there are some slight differences between mesaured and given..

The DC biasing is no problem, I have also tried DCFeed and DCBlck you suggested, and no difference in band.
As regards the package effect, maybe! But I don't think it could cause 10dB gain drop at 15GHz.

Anyway, thank you for your reply! BTW, do you know how to get a FET model for nonlinear simulation? If I can't use the model in ADS library.

Hi, you can create your own transistor model. Here I give you some ideas:

1. Physicals models (Equation based on the physics of the transistor). This model is the industry standard and used a lot of parameters. Right now I am using the BISM3v3 to simulated a CMOS circuits.

2. Black box models (Equation based on measurements). NOT experience here.

3. Empirical models. (The most non linear elements like IDS and CGS are modelled with a equation based on measurements). In my master thesis I validated under different conditions, bias a input power (using one a two tone test) the Curtice’s, Angelov’s, and Chen’s I-V model for MESFET’s and HEMT’s. Here some bibliog..

Angelov, Iltcho, Zirath, Herbert, y Rorsman, Niklas, 1992. “A new empirical nonlinear model for HEMT and MESFET devices”. IEEE Transactions on Microwave Theory and Techniques. 40(12): 2258-2266 p.

Chen, Y.C., Ingram D.L., Yen, H.C., Lai, R., y Streit, D.C., 1998. “A new empirical I-V model for HEMT devices”. IEEE Microwave and Guided Wave Letters. 8(10): 342-344 p.

Curtice, W.R. y M. Ettenberg, 1985. “A non linear GaAs FET model for use in the design of output circuits for power amplifiers”. IEEE Transactions on Microwave Theory and Techniques. vol. MTT-33(12): 1383-1394 p.


4. Neuronals transistors models (Neuron trained with measured data). NOT experience here.


Let me know if you want to implant any of these models.
In the atttachement i send you some results.

Regards
FC

Thank you very much! If I did, I'll let you know, but actually it's not easy for me to get the measurement data, do you know community can offer the measurement data or even model?

BTW does "potencia de entrada" means "input power" and "potencia de salida" means "output power"? Thanks again!

hi,
i think , you must be experenced in PA design using ADS, but i am a beginner , now i am designing a 1W 1G to 10G PA, could you give me some suggestions and design example? thanks a lot for your help!