EM simulation of baluns in CMOS process using HFSS

[vlsi_design2]

Hi,

I want to perform EM simulation of a balun designed in Cadence virtuoso layout. I want to export it as .gds to HFSS and perform the EM simulation. Can anyone provide me step by step tutorial for this?

 

[vlsi_design2]

Hi,
Is .gds file sufficient to perform EM simulation in HFSS? Does it need any other file for process related information?

 

[BigBoss]

Hi,
Is .gds file sufficient to perform EM simulation in HFSS? Does it need any other file for process related information?

Normally yes..

 

[volker@muehlhaus]

Does it need any other file for process related information?

Yes, you will need the correct stackup (materials, thickness) for your technology. Results will be very different depending on the actual technology.

There is no standard file format to import technologies into the EM solver. I had created an RFIC stackup editor that reads Assura procfiles and can convert them to Sonnet or ADS Momentum EM stackups, but HFSS is not supported.
https://muehlhaus.com/products/material-file-utility

 

[vlsi_design2]

Hi volker@muehlhaus,

Thank you very much! I have done EM simulation using ADS momentum and I have S parameter file of the 1:3 balun. I have imported the S param file into nport component in Cadence Virtuoso. Now my question is what should be the port impedances of the primary port and two secondary ports?
I think it should be 50 ohm because while doing EM simulation I specified 50 ohm for each.

 

[volker@muehlhaus]

I think it should be 50 ohm because while doing EM simulation I specified 50 ohm for each.

The S-parameter data is referenced to some impedance (usually 50 Ohm) and that reference impedance value is stored in the file. So when using the S-parameter block, there should be no need to specify the impedance manually.

Now my question is what should be the port impedances of the primary port and two secondary ports?

Port impedance to do what? Use the simulated data in another S-Parameter simulation? Then you should use whatever is realistic in your application. If your balun is loaded with 100 Ohm on the differential side, use that, because that is what matters to you.

The conversion of data inside the S-Parameter block to other external load impedances is done by the simulation software.

 

[vlsi_design2]

Hi volker@muehlhaus,
I want to export touchtone file to cadence using nport component to simulate Z parameters to find Q, K etc. I found that in Cadence schematic the port impedances does not affect the result.

I want to tune out the inductances at primary and secondary using capacitances Cp, Cs1,Cs2 (attached)
Also I want to choose proper secondary load impedances Rs1 and Rs2 (which is theoretically Rs*n^2)
My question is how do I systematically find them and match them?

I tried to simulate and extract Lp, Ls1, Ls2, K1, K2 from Z parameters and then find corresponding Cs. But when I excited primary with AC I see a peak at a different frequency.

 

[volker@muehlhaus]

I want to export touchtone file to cadence using nport component to simulate Z parameters to find Q, K etc. I found that in Cadence schematic the port impedances does not affect the result.

Sounds correct to me. The port impedances used for S-parameter simulation will change the numbers for S-parameters, but of course the Y/Z-parameters are unchanged. Y/Z-parameters do not depend on the external loads. So when you use S-parameter data in a circuit, it doesn't matter what port impedances you had used for EM simulation of the EM block.

I tried to simulate and extract Lp, Ls1, Ls2, K1, K2 from Z parameters and then find corresponding Cs.

The balun in your simplified schematic is purely inductive, but that's an over simplification. It does have parasitics that affect the electrical response, and simulating as an inductor only is very inaccurate. Here is the equivalent circuit model that I used for RFIC inductors:

https://muehlhaus.com/products/equivalent-circuit-model-fit-for-rfic-inductors

Some people extract the effective series inductance and effective series resistance only, but in my opinion that isn't approriate for your work because there are series and shunt path elements.

 

[mustangyhz]

Hi volker@muehlhaus,

Thank you very much! I have done EM simulation using ADS momentum and I have S parameter file of the 1:3 balun. I have imported the S param file into nport component in Cadence Virtuoso. Now my question is what should be the port impedances of the primary port and two secondary ports?
I think it should be 50 ohm because while doing EM simulation I specified 50 ohm for each.

can you tell me how to imported the S param file into nport component in Cadence Virtuoso?
thanks!