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Cadence has multiple electromagnetic (EM) technologies within its product portfolio as of today.  Some came via acquisition and others were created internally.  With a wide breadth of EM simulation and analysis tools within the Cadence product families, you are likely asking yourself what you need to know about them and which one(s) to use.

Let's start with what an EM solver does. First, it takes in a physical description of the conductors, typically layout although for something like a connector it is actually a mechanical model. Second, it processes the layout to get it into a form that can be used in the analysis phase. This typically involves "meshing" the conductors using the finite element method or something that is more optimized due to restrictions on the layout, such as it being planar. The meshing is required since all the analysis methods work on tiny pieces of the conductor where a lot of approximations can be made without significant error, and the overall analysis is done by assembling all of these little pieces of the puzzle into an overall solution. So for each element, the next phase is that the analysis is done based on Maxwell's equations for electromagnetism. These solutions are then combined to give the final result. The result of the analysis is provided as a model (such as S-parameters) that can be used in circuit simulation to verify performance.

Why and When to Do EM Analysis

There are two main reasons to do EM analysis. The first is to see if the signals in the design will meet their performance specifications, and the second is to see whether the design has unintended EM interactions in the circuit/system.

There are also different occasions on which you might want to do EM analysis. The first is that you are designing something (a chip, a package, a board, a system) and you want to see how good your current design is. You expect to look at the result of the analysis and then tweak whatever it is you are designing to further improve it. In this instance, you require high performance and integration. You want to go from your design system (Virtuoso for chips, Allegro for boards, perhaps 3rd party models for connectors) to results as fast as possible. You don't want to have to manually transfer files, manually guide the meshing, manually transfer the results back into your design environment. In fact, you don't want to do anything manual at all, beyond clicking on a menu item to launch the analysis. Also, you are sitting waiting while the analysis takes place, so you don't want to wait a long time for the analysis — a few seconds would be great.

The second reason for doing EM analysis is for signoff. You have finished your design, or at least you hope you have. You want to get confirmation that it is as good as you can make it. In this case, you are less concerned about performance and more concerned about accuracy. You only plan on doing this analysis once, or at most a few times, so you don't mind it being slow as long as you get numbers that are as close as possible to what you will eventually get once your design is manufactured/fabricated. In practice, it is less binary than design versus signoff and, as a design progresses, the tradeoff between runtime and accuracy changes continuously.

So with those basics covered, which are common to all the solvers, let’s take a look at Cadence’s EM technology and understand more where they came from and the benefits of each.

Sigrity

Cadence acquired Sigrity (the company) in 2012. There are various specialized options (such as Sigrity Serial Link Analysis) but for this post, I'll focus on the two that combine to give full EM analysis: Sigrity Extraction and Sigrity Advanced SI. Sigrity is a planar 3D (sometimes called hybrid) solver, meaning that it uses a mostly 2D algorithm with lots of heuristics to deliver something close to the results you would get with a full 3D solver but much faster.

Clarity

The Clarity 3D Solver was developed internally within Cadence and was released last year. I wrote about it on the day it was released in my post Bringing Clarity to System Analysis. I then took a deeper dive in Under the Hood of Clarity and Celsius Solvers.

Clarity is the most general of all the solvers and can handle arbitrary 3D structures. It is the tool of choice when full 3D analysis is required, or when none of the other solvers are appropriate. For example, analysis of a board and a connector, or analysis of a full ball-grid-array (BGA) package. It is also the most scalable of the solvers, having been designed from the start to run in large server farms and cloud data centers, without requiring enormous amounts of memory on any of the servers. Because of its capacity, it is considered system-level analysis. The only thing beyond its scope today is the type of analysis where you put an entire radar unit inside a chamber and analyze the signal three meters away.

EMX

Cadence acquired EMX through its acquisition of Integrand Software earlier this year. I wrote about this at the time of the acquisition in Designing Radios: Integrand and then covered their history and technology in The Integrand Story. As it happens, I did a deep dive into EMX earlier this week in Analyzing On-Chip RF Passives. EMX is optimized for analyzing passives on-silicon. It is optimized for primarily planar conductors and small vias, just like on-chip interconnect. It also has a broad library of PDKs from all the major foundries. This combination means that it delivers quick and accurate results for on-silicon passives in foundry processes. But only for that special case. Luckily, that is a big special case since more and more passives are being moved on-chip.

AWR AXIEM and Analyst

AWR AXIEM software was acquired when Cadence acquired AWR earlier this year, although it was already being sold by Cadence through an OEM agreement. I wrote about that on the day of the acquisition in Cadence to Acquire AWR, and then took a deeper look at the technology in Designing Radios and Radar: AWR. It is optimized for use at the PCB level, and also for more general RF solution in the AWR Microwave Office software. AXIEM was integrated into Virtuoso RF (at the source code level) before the acquisition, as I covered in my post RF Design with Cadence Virtuoso and National Instrument's AXIEM. AWR EM technologies include AXIEM (planar 3D) and Analyst (full 3D). Both are tightly integrated into the Cadence AWR Design Environment platform that targets microwave applications from III-V chips to RF modules and even antennas.  AXIEM s optimized for use at the planar structure level such as PCBs, MMICs, and the like. For more complex designs that are multi-technology such as a microwave/RF module or a system-level design that’s inclusive of a non-planar antenna, Analyst fits the bill.

Making a Choice 

If you need a full 3D solver either because the elements are not sufficiently planar or you are analyzing a large system, then the Clarity 3D Solver is the solution. If you are doing on-chip analysis (CMOS) then EMX is the preferred EM solver. At the board and package level, Sigrity analysis, AWR AXIEM software, and AWR Analyst software are all options and well integrated into Cadence platforms.

Learn More

Each of these solvers has a product page on the Cadence website:

• Sigrity Analysis Point Tools
• Clarity 3D Solver
• EMX Planar 3D Simulator
• AWR AXIEM
• AWR Analyst

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