re： Layout vs schematic simulation results

Hi,

I designed a LCL circuit for testing purposes using 2 micro strips and a chip cappacitor. I run the S parameter on it and i get the expected results but when i generate/update the layout and run the EM the results are totally off. I checked the FR-4 substrate and i changed the capacitor type , added solder pads ,frequency range etc. Compared the two S11 parameters the circuit simulation is -20dB at the desired frequency and -001dB simulated with EM.
I really don't understand why this is happening.

Can you please advise

Thank You
BR ED
PS: I also designed a LPF and all worked out-this schematic is in the same project and uses the same defined substrate

> I really don't understand why this is happening.

You made a mistake somewhere. If you upload the project, someone might be able to help.

Hi

Please see attached.
Thank You
Ed

附图/附件

rectifier101_wrk.zip

If you made a mistake somewhere and you upload the workspace with the design data (schematic and/or layout) that is not empty and not just the simulation results, then someone might be able to help.

Hi
Sorry if this info is missing i apologies. I just archived the whole workspace folder this should have everything. I will try again
Thanks Edward

Hi
I don't know what happened, I actually tested this to make sure that info is there.

Thank You

Ed

附图/附件

rectifier101_wrk.rar

You cannot perform the EM (Momentum) simulation with the SMT capacitor in the layout. This needs to be removed, creating a 4 port model for the transmission line components and with this you create a new schematic with the SMT capacitor connected back inside the EM modelled network to do the s-parameter simulation of the entire network. See attached picture (red - original circuit data, blue - EM co-simulation model)

The latest versions of ADS (ADS 2014.01 or later) include circuit partitioning which can be used to automate this process.

附图/附件

ip_filter.png

Hi

Thank you for your reply. I'm trying to create the four port TL but i cannot find the LTTee component to simulate the ground . I suspect that i didn't import it with a design kit. Can you please advise in what library it is . I looked thru the help file and i didn't find a cross reference.

Cheers Ed

That is not right. You do not need to do anything for ground. This is implied from the use of microstrip models for circuit simulation and the substrate for EM. A ground connection is created at each pin in the port mapping setup.

What you do need though a two extra pins, so each microstrip line has a pin at each end, where the SMT capacitor connects. So you layout becomes two microstrip line with a pin at each end.

附图/附件

ip_filter.png

> the four port TL but i cannot find the LTTee component to simulate the ground

This is a common misunderstand: ports and modes in RF vs. individual nodes in low frequency electronics.

You need only two ports - not four - because the currents in "signal" and "ground" are dependent. The transmission line model will always calculate return current in ground that is equal to the signal current, with opposite direction. So results do include ground path, even if it is not explicitely wired in schematic.

Hi And thank you for the responses.

I tried both advices out and it still doesn't work out. Please bear with me as i only started in ADS, I must do the same mistake it seems or I'm missing something obvious.
I uploaded the latest increment of this work.

Please let me know
Thank You

Ed

附图/附件

rectifier101_wrk.rar

申明：网友回复良莠不齐，仅供参考。如需专业帮助，请学习易迪拓培训专家讲授的ADS视频培训课程。