Virtuoso Meets Maxwell: Help with Electromagnetic Analysis - Part VI

'Virtuoso Meets Maxwell' is a blog series aimed at exploring the capabilities and potential of Virtuoso® RF Solution and Virtuoso MultiTech. So, how does Virtuoso meets Maxwell? Now, the Virtuoso platform supports RF designs, and the RF designers measure the physical and radiation effects by using the Maxwell's equations. In addition to providing insights into the useful software enhancements, this series broadcasts the voices of different bloggers and experts about their knowledge and experience of various tools in the Virtuoso IC-Packaging world along with the nuances of RF, microwave, and high frequency designs. Watch out for our posts on Mondays.

Hello everyone,

This is going to be my last post in this 6-part blog-series titled Help with Electromagnetic Analysis. You can find the links to the previous parts at the end of this blog. Having already discussed process setup, geometry selection, automatic shape pre-processing, comparing accuracy, performance, capacity, memory consumption and usability, and finally, port setup, today I would like to discuss simulation settings for running the Cadence AWR AXIEM 3D Planar EM Analysis from the Virtuoso RF Solution.

Simulation settings mainly comprise of general setup and then solver specific setup. The general setup can be accessed on the first tab of the Simulation Settings form. You should consult online documentation for details on this form (shown below). At a high level, this General tab allows you to set min/max frequencies for simulations and decide if you want to use Advanced Frequency Sweep (AFS).

I definitely recommend enabling Explicit DC Solution. This will ensure that there is a stable model at zero frequency or DC, otherwise you may run into instability issues when using the output S-parameter file with time-domain circuit simulations.

The other part of the simulation setup will be solver-specific, in this case on the AXIEM tab (shown below). This tab allows you to set mesh densities and global settings like thick or thin metal modeling and edge mesh modeling. I generally recommend you to disable Model as Zero Thickness.

Minimum Edge Length controls the size of the mesh and this needs to be smaller than the minimum port width. Note that even though the global Enable De-embedding option may be enabled on this form, the individual settings for the ports under the Ports tab in the Electromagnetic Solver assistant is disabled by default. Since the individual settings will override the global setting on the AXIEM tab, you don’t have to worry about disabling it (remember that we had discussed de-embedding in Part V and had recommended that for typical IC layouts you don’t want to enable de-embedding).

The boundary conditions are typically set as bottom PEC and top open (or, air) and these are usually good default values for a Method Of Moment (MOM) EM solver.

Once the simulation setup is done, it is always a good idea to generate the mesh. This step allows you to look at the number of mesh elements or unknowns reported by the mesher (in the log file and in the CIW) and make an educated guess about the simulation time. Also, unusually high unknowns (in the range of 70K or more) can be a sign of something being setup incorrectly. For example, the minimum edge length might be too small, or vias may not have been clustered properly, or there may be a lot of floating shapes and nets in the layout. I always make sure that these issues are resolved before launching the actual simulation.

Once the simulation is finished the resulting s-parameter file will show up on the Results tab.

By clicking on the first icon, the s-parameter file will directly open in the ADE waveform window. As you can see below, readymade measurements are available there to plot Q, L, R, and C which are useful measurements if you are analyzing inductors.

Also, using the ability to create an extracted view, an n-port pointing to the s-parameter file can be automatically inserted and stitched into the golden schematic, thereby giving a simulation ready EM extracted view. You can also combine the results of electromagnetic analysis with Quantus extracted RC views, but that will be discussed in another blog.

That’s it for today. Please find Part I, Part II, Part III, Part IV, and Part V of this 6-part blog-series titled Help with Electromagnetic Analysis. Next time, I will be back with other topics from Virtuoso RF Solution. Until then, have a safe day!

Related Resources

• Virtuoso RF Solution
• What’s New in Virtuoso (ICADVM18.1 Only)
• Video - Running an Electromagnetic Analysis Using AXIEM
• Virtuoso Electromagnetic Solver User Guide

For more information on Cadence circuit design products and services, visit www.cadence.com.

Contact Us

For any questions, general feedback, or even if you want to suggest a future blog topic, write to custom_ic_blogs@cadence.com.

About Virtuoso Meets Maxwell

Virtuoso Meets Maxwell series includes posts about the next-generation die, package, and board design flow with a focus on reinventing and optimizing the design process to ensure that the designer remains a designer! Keep watching!

Click Subscribe to submit your email address for receiving notifications about our latest Virtuoso Meets Maxwell posts. 

(Sutirtha) Kabir