Custom IC Design Blogs

'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.

Last year, I blogged about Full-Cellview EM Extraction. It is the perfect flow for characterizing passive structures, like inductors or RF blocks from which you manually removed all the active devices.

But what do you do if you want to characterize an RF Block that has a mix of passive and active devices? You definitely don't want to remove the active devices manually. Instead, try the new excluded cells feature in the Electromagnetic Solver assistant of Virtuoso Layout Suite EXL! With just a few mouse clicks, you can exclude any cell for which you have a symbol (the tool needs a symbol so that it can later generate a simulation schematic for you). By the way, this feature is sometimes also referred to as "black boxing".

For example, here is a power amplifier (PA) with a number of transistors, as well as MIMCAPs and resistors for which I want to use an existing simulation model. All I have to do is turn on "Extract Full Cellview" and specify the cells I want to exclude:

There is a handy highlighting feature that will highlight all those shapes that will be sent to the electromagnetic (EM) solver, while any shape from an excluded cell will stay dark. At a glance, I can see if I have the right setup:

The Electromagnetic Solver assistant will automatically insert ports for any excluded cell. And I can review all those ports directly on my layout canvas. I could even edit the ports, like change internal ports to edge ports, or move their location!

When the EM simulation is finished, a simulation schematic, or n-port schematic, is automatically generated. It will contain an n-port instance with S-parameters, as well as a symbol instance of every cell I had excluded. This way I can easily run post-layout simulation of the entire PA.

And the best part: the touchstone file directly lives inside the simulation schematic folder! So, the touchstone file gets checked into the data management system, and there is no separate sparam cellview to keep track of. The entire simulation schematic is a self-contained unit.

Have you used the new excluded cells feature? If you have, we’d be honored to hear your thoughts. We want to evolve the tool along with your products/tools to continue to meet your most demanding requirements. Cadence® is here to help you overcome each and every challenge in RF extraction!

Johannes Grad

Related Resources

• Virtuoso RF Solution
• Virtuoso RF Solution Guide
• Virtuoso Electromagnetic Solver User Guide
• What’s New in Virtuoso

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

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