Virtuoso Meets Maxwell: Making the Ports Ready for Simulations in Clarity 3D Solver

'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!

The principles of Finite Element Method (FEM) dictate that the ports are to be defined in some specific ways. The key interests in FEM simulations are mostly around two types of ports: (a) lumped port and (b) wave port. Out of the two, the lumped ports play a major role in the EM analyses for Virtuoso RF Solution, so we will focus on these ports in this post.

Running simulation in Clarity 3D Solver, a full-wave 3D Finite Element Analysis (FEA) tool for the extraction of the electromagnetic (EM) behavior of electrical designs, has a few requirements for ports, as mentioned below.

Return Path

In my previous blog, I have already mentioned how the FEM tools require a return path for the proper extraction of a non-radiative structure. That means, you can drive a patch antenna without a return path as most of the energy is expected to be radiated. Whereas, for a data transmission line, you need to make sure that the charge comes back to the point where it started after it has traversed the path of the trace and the relevant return path.

Reference Point

The lumped ports are always referenced to a point on the metal return path. In some other methods of electromagnetic simulation (for example, Method of Moment or MoM), a port can be driven without an explicit reference point. However, Clarity 3D Solver works on the FEM principle, so it would require a reference point for its lumped ports.

Port Shapes

The lumped ports are created on two-dimensional rectangular shapes that contain port excitation from one edge to the other (from reference to the excitation point). These ports should not intersect any other metal on their way between the two end points. We cannot make a lumped port between two points if they are not in each other’s ‘line-of-sight’.

If the port count is high, setting up ports by drawing them manually and ensuring that these requirements are met can be tedious.

There is an easier way of creating ports. You can use some very convenient features that come along with Electromagnetic Solver Assistant in Virtuoso Layout Suite EXL, especially in the port creation stage, to take care of all the requirements mentioned above. This assistant has a ‘Magic Wand’ (it literally has a magic wand icon on the button!) that can automatically generate some ports for you.

In addition, there is this extremely easy port addition flow - add a port and then progress through the natural incremental checks: Is it in the same metal layer or in different layers? How wide? Where are the reference and excitation points of this port? You do not need to memorize the coordinates. Simply click on the layout to pick these points. The layers in which the port connects are also shown a drop-down list.

The ports need to follow some rules for simulation. To ensure that the rules are followed, use the “Validate Port” button in the Electromagnetic Solver assistant and check for any irregularity in created ports.

After completing the model definitions in the Electromagnetic Solver assistant, send this information to Clarity 3D Solver for further checks and simulation run.

Apart from editing ports in Virtuoso Layout Suite EXL, it is possible to create ports in Clarity 3D Solver as well. Just a little relevant information here: The Clarity 3D Solver has two main types of GUI interfaces: Clarity 3D layout, which is convenient for 3-D planar structures and Clarity 3D workbench, which is more aimed for arbitrary 3-D structures. Both have their own port-making wizards or flows that are geared towards their particular application and interface. For IC-like structures, it is convenient to work in Clarity 3D layout. However, this difference is just in the appearance. The underlying solver engine is the same. You can launch both the tools from Virtuoso Layout Suite EXL.

Let’s take a sneak peek at how these ports look like in Clarity 3D Solver. We can view the port list and select one or more ports. The selected ports are highlighted on the canvas, as shown below:

You may notice how one end of the port has a green circle. This denotes the ‘reference’ point for the port. The yellow box is the port’s shape. It is important to keep all corners of this yellow rectangle inside, i.e. the corners of this yellow shape should not be out of the metal.

Such a convenience offered by both the tools can cut down the time usually spent while manually setting up ports for electromagnetic simulation. In addition to this, the complete flow of Virtuoso RF Solution allows you to use the EM simulation results right away when you go back from Clarity 3D Solver to Virtuoso Layout Suite EXL. There are many other great features that make the combo of the two products offered by Cadence very effective and convenient for use in design flows. I encourage you to explore these further if you are using electromagnetic simulation on your layouts in Virtuoso Layout Suite. You may find something that suits your tasks and makes your workflow more streamlined.

Thanks for reading!

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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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Amir Asif