Questions about EM simulation of LNA.

[htforever]

Has anyone ever used ADS Momentum to simulate a LNA?
Is that necessary?

I have several questions to ask:
1, how to describe the Low Noise transistor in Mom?
I have only a S2P file to make s-parameter simulation in schematic window, so what to use in Mom?

2,How to deal with the ground ports in Mom?

3,How to deal with the lumped components in Mom?
Such as R,L,C.

 

[radiohead]

Yes I have simulated an LNA, with the aid of momentum. And yes, it is needed. For LNA the differences will be minor, but apparent. But for VCO's the difference is very big!

The right way to do it is by first putting a lot of ports of your momentum layout, everywhere where you want to connect a lumped element. Then you simulate the EM structure's S-parameters. Then you save this set and include this in your circuit simulator to simulate the behaviour with the influence of the interconnects.

Because this is not an easy task if you put a lot of components, ADS introduces layout components in ADS 2003A. This means they make it possible to integrate a graphical view of the layout into the circuit simulator. You just have to connect the lumped elements at theright spot.

One problem: forget about DC. The EM does not spawn a correct DC model for the circuit. Agilent claims to have corrected this in the ADS 2003C version, but I have not been able to verify this.

 

[htforever]

Hi, radiohead:
Thanks very much for your reply.
Now I have basic concept on EM simulation of LNA.
Could you please share your design project file with
me?
If it's related to copyright, please forgive me request. I can understand.
PS: what's the Heart of Europe?

 

[radiohead]

Nope, no can do.

There's a lot of tutorials out there.

 

[v4eda]

Has anyone ever used @DS Momentum to simulate a LNA?
Is that necessary?

I have several questions to ask:
1, how to describe the Low Noise transistor in Mom?
I have only a S2P file to make s-parameter simulation in schematic window, so what to use in Mom?

2,How to deal with the ground ports in Mom?

3,How to deal with the lumped components in Mom?
Such as R,L,C.

yeah Momentum can be used to simulate amplifiers but without the active device! To simulate any active circuit in momentum, it's best to break the circuit into parts (like the input and the output match,any intermediate stage for a two stage design). you need to introduce ports wherever you desire connectivity to lumped elements or to the active device; so eventually you may land up with a 4 or 5 port network in momentum;
it's always better to check the possibility of using momentum in RF mode if your circuit is electrically smaller than than the concerned frequency of operation (circuit dimensions are < lambda/10);
Once you get the desired S4P or S5P file from momentum results put it back in the schematic (look out for the correct connections!) and simulate the circuit!
8) Sometimes if the structure is too complicated it requires a bit of experience in breaking the circuit into parts as improper sections would result in erroneous results in schematic.

 

[BigBoss]

Co-simulation should be used in ADS with a layout that has been already simulated in Momentum. When you simulate a layout, you should put the ports that will inputs , outputs and interconnections of the layout. For instance consider a one input port, one output port and many internal ports on a layout.

First it should be simulated in momentum and created component as layout view. Then this view is used to connect transistors, capacitors etc. at each port and you can simualte whatever you wish like s-parameters or harmonic balance or system simulation.

Because this layout has been defined N port black box with s-parameters.
A sample circuit co-simulation is shown below.