Learning Forum

[JakobW]

Dear Sir or Madam,nI have an HFSS model with 2 waveports (In, Out) and 2 Lumped RLC elements. The lumped elements are assigned to 20 Ohm and 75 fF, and located between the ground and a microstrip connecting the In and Out waveports. nI want to replace the Lumped RLC elements with Lumped Ports so that I can connect it in Circuit to an interface port (of 20 Ohm) and a capacitor of 75 fF (in parallel). I am wondering which impedance I should use for the lumped ports. My approach is to think of lumped elements so that a 0.1 Ohm lumped Port impedance (a short) is in series with the RC circuit, which I connect in Circuit. However, the result diverges from the HFSS analysis significantly. Another approach would be to think of matching the lumped port in HFSS with the lumped elements in Circuit (e.g. 20 Ohm lumped Port Impedance). The agreement with the Lumped RLC simulation is much better, but in this setup, I would need to re-simulate the HFSS model every time I change the resistance. I also found that a Lumped Port impedance of 1 Ohm gives already a good agreement with the Lumped RLC simulation.nnCould you please give me some advice on which way of defining the Lumped Port is the best practice?.Thank you a lot,nJakobnnPS: I also replaced the Lumped RLC element with a lumped port sheet (20 Ohm) in parallel with a Lumped RLC sheet of 75 fF in HFSS. I used the results of this model additionally to the Lumped RLC (20 Ohm and 75 fF) model for comparison of the Circuit result. The two HFSS results agree with some minor differences.n

[Praneeth]

Hi Jacob,nPlease share snap shots of your simulation interface where you have wave port and lumped elements to help us serve you better.nAlso share the snapshots of how you are defining the wave port and lumped RLC components.nKindly elaborate on how you want to use the defined lumped port in the circuit.nBest Regards,n

[JakobW]

Hello, nApologies for the way I asked my question. It is the first time I ask something in a forum.nnMy HFSS design is shown in Solving_in_HFSS_only.png. The port definition is shown in Solving_in_HFSS_only_Port_Definition.png. I have also combined the lumped Port and Lumped RLC in a single Lumped-RLC (with the resistance of the lumped Port). The results agree between these models.nMy goal is to define the lumped RLC and Lumped Port in Circuit, as shown in Setup_in_Circuit.png. For this, I removed the lumped RLC in the HFSS model, as shown in Solving_in_HFSS_for_Circuit.png, and defined the lumped Port as short (0.1 Ohm, Solving_in_HFSS_for_Circuit_Port_Definition.png). After connecting and evaluating the model in Circuit (Setup_in_Circuit.png), the returnloss is much worse. However, when I set the lumped port resistance in Solving_in_HFSS_for_Circuit_Port_Definition.png to 1 Ohm or more, the Circuit model result agrees with the HFSS only model again. nI wonder about the best practice of defining the lumped ports in HFSS, which are connected to a capacitor and an interface port in Circuit.n

[Praneeth]

HiArray,nPlease use upload image option to upload your screenshots as we cannot access the attachments of the forum.nBest Regards,n

[JakobW]

Hello,nI am so sorry, let's give it another try:nMy HFSS design and the port definition looks like the followingnTo use this model in Circuit, I removed the lumped RLC in the HFSS model and defined the lumped Port as short:nnnI am importing the model into Circuit, where I connect it in the following waynnThe question is about how to define the lumped ports in HFSS so that the model can be used in Circuit.Thank you,nJakobn

[Praneeth]

nThank you for sharing the screenshots of your simulation model. nI would like to know the functionality of your model to serve you better. What is the nature of the material (green color solid) in which you are defining Lumped elements and lumped ports. I am guessing it to be some conductor material. Please confirm.nBest Regards,n

[JakobW]

,nPlease excuse the later reply.nThe green-coloured solid is assigned to PEC with a surface impedance representing the surface impedance of a superconductor. The boundary of the model below the trace is also assigned to this surface impedance (Ground Plane).nThe Lumped Ports represent superconducting tunnel junctions, where each has a resistivity and capacitance associated. During the design stage, I might need to vary its size, which causes the resistance and capacitance to vary. I want to do these changes in Circuit rather than re-simulating the HFSS design. I am not sure how to define the lumped port for such a setup.nThank you,nJakobn

[Praneeth]

Hi,nWe appreciate for your patience on this..nPlease go through the following picture and check whether this is the scenario that you are trying to simulate.nBest Regards,n