All Things Ansys 060: Tips For Making Working From Home More Productive

 

Published on: April 6th, 2020
With: Eric Miller & Matt Sutton
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s seasoned expert at working with Ansys from home Matt Sutton for a quick discussion on tips and best practices that make working from home more productive and effective.

If you would like to learn more about how PADT and Ansys can help you to better run your simulation from your home office, check out our webinar on the topic here: https://bit.ly/3dSa8WN

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Efficient and Accurate Simulation of Antenna Arrays in HFSS

Unit-cell in HFSS

HFSS offers different method of creating and simulating a large array. The explicit method, shown in Figure 1(a) might be the first method that comes to our mind. This is where you create the exact CAD of the array and solve it. While this is the most accurate method of simulating an array, it is computationally extensive. This method may be non-feasible for the initial design of a large array. The use of unit cell (Figure 1(b)) and array theory helps us to start with an estimate of the array performance by a few assumptions. Finite Array Domain Decomposition (or FADDM) takes advantage of unit cell simplicity and creates a full model using the meshing information generated in a unit cell. In this blog we will review the creation of unit cell. In the next blog we will explain how a unit cell can be used to simulate a large array and FADDM.

Fig. 1 (a) Explicit Array
Fig. 1 (b) Unit Cell
Fig. 1 (c) Finite Array Domain Decomposition (FADDM)

In a unit cell, the following assumptions are made:

  • The pattern of each element is identical.
  • The array is uniformly excited in amplitude, but not necessarily in phase.
  • Edge affects and mutual coupling are ignored
Fig. 2 An array consisting of elements amplitude and phases can be estimated with array theory, assuming all elements have the same amplitude and element radiation patterns. In unit cell simulation it is assumed all magnitudes (An’s) are equal (A) and the far field of each single element is equal.

A unit cell works based on Master/Slave (or Primary/Secondary) boundary around the cell. Master/Slave boundaries are always paired. In a rectangular cell you may use the new Lattice Pair boundary that is introduced in Ansys HFSS 2020R1. These boundaries are means of simulating an infinite array and estimating the performance of a relatively large arrays. The use of unit cell reduces the required RAM and solve time.

Primary/Secondary (Master/Slave) (or P/S) boundaries can be combined with Floquet port, radiation or PML boundary to be used in an infinite array or large array setting, as shown in Figure 3.

Fig. 3 Unit cell can be terminated with (a) radiation boundary, (b) Floquet port, (c) PML boundary, or combination of them.

To create a unit cell with P/S boundary, first start with a single element with the exact dimensions of the cell. The next step is creating a vacuum or airbox around the cell. For this step, set the padding in the location of P/S boundary to zero. For example, Figure 4 shows a microstrip patch antenna that we intend to create a 2D array based on this model. The array is placed on the XY plane. An air box is created around the unit cell with zero padding in X and Y directions.

Fig. 4 (a) A unit cell starts with a single element with the exact dimensions as it appears in the lattice
Fig. 4 (b) A vacuum box is added around it

You notice that in this example the vacuum box is larger than usual size of quarter wavelength that is usually used in creating a vacuum region around the antenna. We will get to calculation of this size in a bit, for now let’s just assign a value or parameter to it, as it will be determined later. The next step is to define P/S to generate the lattice. In AEDT 2020R1 this boundary is under “Coupled” boundary. There are two methods to create P/S: (1) Lattice Pair, (2) Primary/Secondary boundary.

Lattice Pair

The Lattice Pair works best for square lattices. It automatically assigns the primary and secondary boundaries. To assign a lattice pair boundary select the two sides that are supposed to create infinite periodic cells, right-click->Assign Boundary->Coupled->Lattice Pair, choose a name and enter the scan angles. Note that scan angles can be assigned as parameters. This feature that is introduced in 2020R1 does not require the user to define the UV directions, they are automatically assigned.

Fig. 5 The lattice pair assignment (a) select two lattice walls
Fig. 5 (b) Assign the lattice pair boundary
Fig. 5 (c) After, right-click and choosing assign boundary > choose Lattice Pair
Fig. 5 (d) Phi and Theta scan angles can be assigned as parameters

Primary/Secondary

Primary/Secondary boundary is the same as what used to be called Master/Slave boundary. In this case, each Secondary (Slave) boundary should be assigned following a Primary (Master) boundary UV directions. First choose the side of the cell that Primary boundary. Right-click->Assign Boundary->Coupled->Primary. In Primary Boundary window define U vector. Next select the secondary wall, right-click->Assign Boundary->Couple->Secondary, choose the Primary Boundary and define U vector exactly in the same direction as the Primary, add the scan angles (the same as Primary scan angles)

Fig. 6 Primary and secondary boundaries highlights.

Floquet Port and Modes Calculator

Floquet port excites and terminates waves propagating down the unit cell. They are similar to waveguide modes. Floquet port is always linked to P/S boundaries. Set of TE and TM modes travel inside the cell. However, keep in mind that the number of modes that are absorbed by the Floquet port are determined by the user. All the other modes are short-circuited back into the model. To assign a Floquet port two major steps should be taken:

Defining Floquet Port

Select the face of the cell that you like to assign the Floquet port. This is determined by the location of P/S boundary. The lattice vectors A and B directions are defined by the direction of lattice (Figure 7).

Fig. 7 Floquet port on top of the cell is defined based on UV direction of P/S pairs

The number of modes to be included are defined with the help of Modes Calculator. In the Mode Setup tab of the Floquet Port window, choose a high number of modes (e.g. 20) and click on Modes Calculator. The Mode Table Calculator will request your input of Frequency and Scan Angles. After selecting those, a table of modes and their attenuation using dB/length units are created. This is your guide in selecting the height of the unit cell and vaccume box. The attenation multiplied by the height of the unit cell (in the project units, defined in Modeler->Units) should be large enough to make sure the modes are attenuated enough so removing them from the calcuatlion does not cause errors. If the unit cell is too short, then you will see many modes are not attenuated enough. The product of the attenuatin and height of the airbox should be at least 50 dB. After the correct size for the airbox is calcualted and entered, the model with high attenuation can be removed from the Floquet port definition.

The 3D Refinement tab is used to control the inclusion of the modes in the 3D refinement of the mesh. It is recommended not to select them for the antenna arrays.

Fig. 8 (Left) Determining the scan angles for the unit cell, (Right) Modes Calculator showing the Attenuation

In our example, Figure 8 shows that the 5th mode has an attenuation of 2.59dB/length. The height of the airbox is around 19.5mm, providing 19.5mm*2.59dB/mm=50.505dB attenuation for the 5th mode. Therefore, only the first 4 modes are kept for the calculations. If the height of the airbox was less than 19.5mm, we would need to increase the height so accordingly for an attenuation of at least 50dB.

Radiation Boundary

A simpler alternative for Floquet port is radiation boundary. It is important to note that the size of the airbox should still be kept around the same size that was calculated for the Floquet port, therefore, higher order modes sufficiently attenuated. In this case the traditional quarter wavelength padding might not be adequate.

Fig. 9 Radiation boundary on top of the unit cell

Perfectly Matched Layer

Although using radiation boundary is much simpler than Floquet port, it is not accurate for large scan angles. It can be a good alternative to Floquet port only if the beam scanning is limited to small angles. Another alternative to Floquet port is to cover the cell by a layer of PML. This is a good compromise and provides very similar results to Floquet port models. However, the P/S boundary need to surround the PML layer as well, which means a few additional steps are required. Here is how you can do it:

  1. Reduce the size of the airbox* slightly, so after adding the PML layer, the unit cell height is the same as the one that was generated using the Modes Calculation. (For example, in our model airbox height was 19mm+substrte thickness, the PML height was 3mm, so we reduced the airbox height to 16mm).
  2. Choose the top face and add PML boundary.
  3. Select each side of the airbox and create an object from that face (Figure 10).
  4. Select each side of the PML and create objects from those faces (Figure 10).
  5. Select the two faces that are on the same plane from the faces created from airbox and PML and unite them to create a side wall (Figure 10).
  6. Then assign P/S boundary to each pair of walls (Figure 10).

*Please note for this method, an auto-size “region” cannot be used, instead draw a box for air/vacuum box. The region does not let you create the faces you need to combine with PML faces.

Fig. 10 Selecting two faces created from airbox and PML and uniting them to assign P/S boundaries

The advantage of PML termination over Floquet port is that it is simpler and sometimes faster calculation. The advantage over Radiation Boundary termination is that it provides accurate results for large scan angles. For better accuracy the mesh for the PML region can be defined as length based.

Seed the Mesh

To improve the accuracy of the PML model further, an option is to use length-based mesh. To do this select the PML box, from the project tree in Project Manager window right-click on Mesh->Assign Mesh Operation->On Selection->Length Based. Select a length smaller than lambda/10.

Fig. 11 Using element length-based mesh refinement can improve the accuracy of PML design

Scanning the Angle

In phased array simulation, we are mostly interested in the performance of the unit cell and array at different scan angles. To add the scanning option, the phase of P/S boundary should be defined by project or design parameters. The parameters can be used to run a parametric sweep, like the one shown in Figure 12. In this example the theta angle is scanned from 0 to 60 degrees.

Fig. 12 Using a parametric sweep, the scanned patterns can be generated

Comparing PML and Floquet Port with Radiation Boundary

To see the accuracy of the radiation boundary vs. PML and Floquet Port, I ran the simulations for scan angles up to 60 degrees for a single element patch antenna. Figure 13 shows that the accuracy of the Radiation boundary drops after around 15 degrees scanning. However, PML and Floquet port show similar performance.

Fig. 13 Comparison of radiation patterns using PML (red), Floquet Port (blue), and Radiation boundary (orange).

S Parameters

To compare the accuracy, we can also check the S parameters. Figure 14 shows the comparison of active S at port 1 for PML and Floquet port models. Active S parameters were used since the unit cell antenna has two ports. Figure 15 shows how S parameters compare for the model with the radiation boundary and the one with the Floquet port.

Fig. 14 Active S parameter comparison for different scan angles, PML vs. Floquet Port model.
Fig. 15 Active S parameter comparison for different scan angles, Radiation Boundary vs. Floquet Port model.

Conclusion

The unit cell definition and options on terminating the cell were discussed here. Stay tuned. In the next blog we discuss how the unit cell is utilized in modeling antenna arrays.

Test, Design & Analyze From Home With Ansys Simulation Software – Webinar

As companies are closing their doors in order to help ensure the health and safety of their employees and customers, those that can are pivoting to working form home.

But what about those working on product design, testing, and analysis that require a physical presence?

Here at PADT we know that the show must go on, and companies working across various technical professions are needed to keep the world moving forward, especially in these trying times. Thus we would like to introduce a solution: Ansys Engineering Simulation Software.

Join The PADT team for a panel discussion on how you can use simulation to move your in-person workflow to a digital environment, as well as what specific Ansys tools can be used to access your work from home.

All of this will be followed by a live Q&A in which our expert staff will take any questions regarding your specific concerns with transitioning your workflow and all other things related to working from home.

Register Here

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All Things Ansys 059: Elements, Contact & Solver Updates in Ansys MAPDL 2020 R1

 

Published on: March 23rd, 2020
With: Eric Miller, Ted Harris, Alex Grishin & Joe Woodward
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Ted Harris, Alex Grishin, and Joe Woodward to discuss their favorite features in the MAPDL Updates in Ansys 2020 R1.

If you would like to learn more about this topic, you can view PADT’s webinar covering these updates here: https://bit.ly/2WD88vt

Additionally, if you would like to take part in the survey mentioned at the start of the episode click the link here: https://bit.ly/3biWkCp

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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MAPDL – Elements, Contact & Solver Updates in Ansys 2020 R1 – Webinar

The ANSYS finite element solvers enable a breadth and depth of capabilities unmatched by anyone in the world of computer-aided simulation. Thermal, Structural, Acoustic, Piezoelectric, Electrostatic and Circuit Coupled Electromagnetics are just an example of what can be simulated. Regardless of the type of simulation, each model is represented by a powerful scripting language, the ANSYS Parametric Design Language (APDL).

APDL is the foundation for all sophisticated features, many of which are not exposed in the Workbench Mechanical user interface. It also offers many conveniences such as parameterization, macros, branching and looping, and complex math operations. All these benefits are accessible within the ANSYS Mechanical APDL user interface.

Join PADT’s Principle & Co-Owner Eric Miller for a look at what’s new for MAPDL in ANSYS 2020 R1, regarding:

  • Linear Dynamics
  • Elements
  • Contacts
  • Post Processing
  • Solver Components
  • And Much More

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All Things Ansys 058: Combining Mechanical Simulation with Additive Manufacturing

 

Published on: March 9th, 2020
With: Eric Miller, Matt Humrick & Pam Waterman
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by 3D Printing Applications Engineer Pamela Waterman and Advatech Pacific’s Engineering Manager Matt Humrick for a discussion on real world applications for topology optimization, and it’s value when it comes to creating parts though additive manufacturing.

If you would like to learn more about this topic and what Advatech Pacific is doing, you can download our case study covering these topics here: https://bit.ly/38Bqu2b

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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3D Design Updates in ANSYS 2020 R1 – Webinar

The ANSYS Discovery 3D Design family of products enables CAD modeling and simulation for all design engineers. Since the demands on today’s design engineer to build optimized, lighter and smarter products are greater than ever, using the appropriate design tools is more important than ever. With ANSYS you can explore ideas, iterate, and innovate with unprecedented speed early in your design process. Delve deeper into design details, refine concepts and perform multiple physics simulations — backed by ANSYS solvers — to better account for real-world behaviors.

Capabilities in this tool-set allow engineers to increase speed and reduce costs from the start of the design cycle, all the way to product launch. Improve engineering productivity and accelerate development time, create higher-quality products while reducing development & manufacturing costs, and respond quickly to changing customer demands while bringing new products to market faster than the competition.

Join PADT’s Training & Support Application Engineer, Robert McCathren for a look at whats new & improved when it comes to these tools in ANSYS 2020 R1. This update includes new releases for ANSYS Discovery Live, AIM, and SpaceClaim, focusing on areas including:

  • Simulation of Thin Parts
  • Topology Optimization in Discovery Live
  • Structural Material Properties
  • Physics Aware Meshing
  • Beam and Shell Modeling
  • And much more

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All Things ANSYS 057: Simulation for Additive Manufacturing in ANSYS 2020 R1

 

Published on: February 24th, 2020
With: Eric Miller & Doug Oatis
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by Lead Mechanical Engineer Doug Oatis for a discussion on the latest advancements in simulation for additive manufacturing and topology optimization in ANSYS 2020 R1.

If you would like to learn more about what this release is capable of, check out our webinar on the topic here:

https://www.brighttalk.com/webcast/15747/384528

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Additive Manufacturing & Topology Optimization in ANSYS 2020 R1 – Webinar

ANSYS offers a complete simulation workflow for additive manufacturing (AM) that allows you to transition your R&D efforts for metal additive manufacturing into a successful manufacturing operation. This best-in-class solution for additive manufacturing enables simulation at every step in your AM process. It will help you optimize material configurations and machine and parts setup before you begin to print. As a result, you’ll greatly reduce — and potentially eliminate — the physical process of trial-and- error testing.

ANSYS additive solutions continue to evolve at a rapid pace. A variety of new enhancements and features come as part of ANSYS 2020 R1, including the ability to work with EOS printers, using the inherent strain approach in ANSYS Workbench Additive, and new materials in ANSYS Additive Print and Science.

Join PADT’s Lead Mechanical Engineer Doug Oatis for an exploration of the ANSYS tools that help to optimize additive manufacturing, and what new capabilities are available for them when upgrading to ANSYS 2020 R1. This presentation includes updates regarding:

  • Level-set topology optimization
  • Density based topology optimization
  • Inherent strain method in workbench Additive
  • Improved supports in Additive Prep
  • Additive Wizard update
  • And much more

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All Things ANSYS 056: A Unique Perspective on a Unique Solution – PADT Sales Talks ANSYS Applications

 

Published on: February 10th, 2020
With: Eric Miller, Bob Calvin, Dan Christensen, Brian Benbow, Heather Dean, Ian Scott & Will Kruspe
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by Bob Calvin, Dan Christensen, Brian Benbow, Heather Dean, Ian Scott, and Will Kruspe from PADT’s ANSYS sales team to discuss the benefits they see in ANSYS as a solution for their unique customer bases, as well as for manufacturers and engineers as a whole. With a combination of technical know-how and knowledge of positioning within different industries, the PADT sales team shares a unique perspective on the value of the various tools that make up the ANSYS suite and how users can best take advantage of them in order to help them succeed.

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Introducing the Stratasys J826 – Full-color, multi-material printing for the enterprise design world

Taking risks attempting to capture design intent at the end of the process requires a lot of post-processing (coloring, assemblies, a mix of technologies, etc.) – when its too time consuming, expensive and late to make changes or correct errors. Stratasys PolyJet 3D printing technology is developed to elevate designs by realizing ideas more quickly and more accurately and taking color copies to the next level.

By putting realistic models in a designer’s hands earlier in the process, companies can promote better decisions and a superior final product. Now, with the Stratasys J8 Series, the same is true for prototypes. This tried and tested technology simplifies the entire design process, streamlining workflows so you can spend more time on what matters –creating, refining, and designing the best product possible.

PADT is excited to introduce the new Stratasys J826 3D printer 

Based on J850 technology, the J826 supplies the same end-to-end solution for the design process and ultra-realistic simulation at a lower price point.
Better communicate design intent and drive more confident results with prototypes that realistically portray an array of design alternatives.

The Stratasys J826 3D Printer is able to deliver realism, shorter time to market, and streamlined application thanks to a variety of unique attributes that set it apart from most other Polyjet printers:

  • High Quality – The J826 can accurately print smaller features at a layer thickness of 14µm to 27µm. As part of the J8 series of printers it is also capable of printing in ultra-realistic Pantone validated colors.
  • Speed & Productivity – Three printing speed modes (high speed, high quality & high mix) allows the J826 to always operate at the most efficient speed for each print. It can also avoid unnecessary down-time associate with material changeovers thanks to it’s built-in material cabinet and workstation.
  • Easy to Use – A smooth workflow with the J826 comes from simple integration with the CAD format of your choice, as well as a removable tray for easy clean up, and automated support creation and removal.

Are you ready to learn how the new Stratasys J826 provides the same quality and accuracy as other J8 series printers at a lower cost?

Provide the requested information via the form linked below and one of PADT’s additive experts will reach out to share more on what makes this new offering so exciting for the enterprise design world.

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All Things ANSYS 055: Introducing ANSYS 2020

 

Published on: February 3rd, 2020
With: Eric Miller, Josh Stout, Sina Gohds, Ted Harris & Tom Chadwick
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by Josh Stout, Sina Gohds, Ted Harris, and Tom Chadwick from the simulation support team to discuss their thoughts on ANSYS 2020 R1, and what specific capabilities they are excited about exploring after attending the annual ANSYS sales kickoff in Florida.

This new release covers updates for the entirety of the ANSYS suite of tools, so there is a lot to talk about.

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Fluent Updates in ANSYS 2020 R1 – Webinar

Computational fluid dynamics (CFD) can be challenging for a multitude of reasons, but not with ANSYS Fluent. Anyone can get great CFD simulation results with ANSYS solutions. Fluent software contains the broad, physical modeling capabilities needed to model flow, turbulence, heat transfer and reactions for industrial applications. These range from air flow over an aircraft wing to combustion in a furnace, from bubble columns to oil platforms, from blood flow to semiconductor manufacturing and from clean room design to wastewater treatment plants.

Fluent spans an expansive range, including special models, with capabilities to model in-cylinder combustion, aero-acoustics, turbomachinery and multiphase systems. The latest innovations and updates simplify and speed setup and meshing while adding even more accurate physical models. The outcome: great results, without compromise.

Join PADT’s Senior CFD & FEA Application Engineer, Sina Ghods, for a look at what’s new and improved in this latest version of ANSYS Fluent, including:

  • User Interface/Graphics
  • Meshing Workflows
  • Multi-phase Robustness
  • Solver Enhancements
  • And much more

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Mechanical Updates in ANSYS 2020 R1 – Webinar

With ANSYS structural analysis software, users are able to solve more complex engineering problems, faster and more efficiently than ever before. Customization and automation of structural solutions is much easier to optimize thanks to new and innovative finite element analysis (FEA) tools available in this product suite.

Once again, ANSYS is able to cement their role as industry leaders when it comes to usability, productivity, and reliability; adding innovative functionality to an already groundbreaking product offering. ANSYS Mechanical continues to be used throughout the industry, and for good reason as it enables engineers to optimize their product design and reduce the costs of physical testing.

Join PADT’s Senior Mechanical Engineer & Lead Trainer Joe Woodward, for an in-depth look at what’s new in the latest version of ANSYS Mechanical, including updates regarding:

  • External Modeling
  • Graphics
  • Composites
  • Linear Dynamics
  • And much more

Register Here

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Reduce EMI with Good Signal Integrity Habits

Recently the ‘Signal Integrity Journal’ posted their ‘Top 10 Articles’ of 2019. All of the articles included were incredible, however, one stood out to me from the rest – ‘Seven Habits of Successful 2-Layer Board Designers’ by Dr. Eric Bogatin (https://www.signalintegrityjournal.com/blogs/12-fundamentals/post/1207-seven-habits-of-successful-2-layer-board-designers). In this work, Dr. Bogatin and his students were developing a 2-Layer printed circuit board (PCB), while trying to minimize signal and power Integrity issues as much as possible. As a result, they developed a board and described seven ‘golden habits’ for this board development. These are fantastic habits that I’m confident we can all agree with. In particular, there was one habit at which I wanted to take a deeper look:

“…Habit 4: When you need to route a cross-under on the bottom layer, make it short. When you can’t make it short, add a return strap over it..”

Generally speaking, this habit suggests to be very careful with the routing of signal traces over the gap on the ground plane. From the signal integrity point of view, Dr. Bogatin explained it perfectly – “..The signal traces routed above this gap will see a gap in the return path and generate cross talk to other signals also crossing the gap..”. On one hand, crosstalk won’t be a problem if there are no other nets around, so the layout might work just fine in that case. However, crosstalk is not the only risk. Fundamentally, crosstalk is an EMI problem. So, I wanted to explore what happens when this habit is ignored and there are no nearby nets to worry about.

To investigate, I created a simple 2-Layer board with the signal trace, connected to 5V voltage source, going over an air gap. Then I observed the near field and far field results using ANSYS SIwave solution. Here is what I found.

Near and Far Field Analysis

Typically, near and far fields are characterized by solved E and H fields around the model. This feature in ANSYS SIwave gives the engineer the ability to simulate both E and H fields for near field analysis, and E field for Far Field analysis.

First and foremost, we can see, as expected, that both near and far Field have resonances at the same frequencies. Additionally, we can observe from Figure 1 that both E and H fields for near field have the largest radiation spikes at 786.3 MHz and 2.349GHz resonant frequencies.

Figure 1. Plotted E and H fields for both Near and Far Field solutions

If we plot E and H fields for Near Field, we can see at which physical locations we have the maximum radiation.

Figure 2. Plotted E and H fields for Near field simulations

As expected, we see the maximum radiation occurring over the air gap, where there is no return path for the current. Since we know that current is directly related to electromagnetic fields, we can also compute AC current to better understand the flow of the current over the air gap.

Compute AC Currents (PSI)

This feature has a very simple setup interface. The user only needs to make sure that the excitation sources are read correctly and that the frequency range is properly indicated. A few minutes after setting up the simulation, we get frequency dependent results for current. We can review the current flow at any simulated frequency point or view the current flow dynamically by animating the plot.

Figure 3. Computed AC currents

As seen in Figure 3, we observe the current being transferred from the energy source, along the transmission line to the open end of the trace. On the ground layer, we see the return current directed back to the source. However at the location of the air gap there is no metal for the return current to flow, therefore, we can see the unwanted concentration of energy along the plane edges. This energy may cause electromagnetic radiation and potential problems with emission.

If we have a very complicated multi-layer board design, it won’t be easy to simulate current flow on near and far fields for the whole board. It is possible, but the engineer will have to have either extra computing time or extra computing power. To address this issue, SIwave has a feature called EMI Scanner, which helps identify problematic areas on the board without running full simulations.

EMI Scanner

ANSYS EMI Scanner, which is based on geometric rule checks, identifies design issues that might result in electromagnetic interference problems during operation. So, I ran the EMI Scanner to quickly identify areas on the board which may create unwanted EMI effects. It is recommended for engineers, after finding all potentially problematic areas on the board using EMI Scanner, to run more detailed analyses on those areas using other SIwave features or HFSS.

Currently the EMI Scanner contains 17 rules, which are categorized as ‘Signal Reference’, ‘Wiring/Crosstalk’, ‘Decoupling’ and ‘Placement’. For this project, I focused on the ‘Signal Reference’ rules group, to find violations for ‘Net Crossing Split’ and ‘Net Near Edge of Reference’. I will discuss other EMI Scanner rules in more detail in a future blog (so be sure to check back for updates).

Figure 4. Selected rules in EMI Scanner (left) and predicted violations in the project (right)

As expected, the EMI Scanner properly identified 3 violations as highlighted in Figure 4. You can either review or export the report, or we can analyze violations with iQ-Harmony. With this feature, besides generating a user-friendly report with graphical explanations, we are also able to run ‘What-if’ scenarios to see possible results of the geometrical optimization.

Figure 5. Generated report in iQ-Harmony with ‘What-If’ scenario

Based on these results of quick EMI Scanner, the engineer would need to either redesign the board right away or to run more analysis using a more accurate approach.

Conclusion

In this blog, we were able to successfully run simulations using ANSYS SIwave solution to understand the effect of not following Dr.Bogatin’s advice on routing the signal trace over the gap on a 2-Layer board. We also were able to use 4 different features in SIwave, each of which delivered the correct, expected results.

Overall, it is not easy to think about all possible SI/PI/EMI issues while developing a complex board. In these modern times, engineers don’t need to manufacture a physical board to evaluate EMI problems. A lot of developmental steps can now be performed during simulations, and ANSYS SIwave tool in conjunction with HFSS Solver can help to deliver the right design on the first try.

If you would like more information or have any questions please reach out to us at info@padtinc.com.