Simulation Workflow from Ansys Electronic Desktop Circuit to Ansys HFSS

ANSYS Electronics Desktop (AEDT) is a collection of powerful tools for simulation. AEDT Circuit provides time domain as well as frequency domain analyses. AEDT Circuit has high execution speed and robust ability to handle circuits of active and passive elements. Analysis types range from DC, Linear Networks (frequency domain), Transient, Oscillator, TV Noise, Envelope, Harmonic Balance, VerifEye (Statistical Eye Diagram), AMI Analysis, and more, with integrated support for additional co-simulation with tools like HSPICE or Matlab.

AEDT Circuit also provides an easy way to create and simulate planar structures such as microstrip, stripline, coupled lines, co-planar strips, co-planar waveguides, and other Printed Circuit Board (PCB) elements which can then be converted into a physical layout of the PCB. In this blog a simple workflow is explained to generate and model a planar structure in Circuit, then export the circuit model to HFSS 3D layout and HFSS for further analysis.

Define your substrate:

After inserting a Circuit Design, right-click on Data under project tree, choose Add Substrate Definition. This brings you to Substrate Defintion window that gives you many optios of substate types. You can choose the type of substarte you need and enter the dielectric and trace metalization information as shown in Figure 1. This substrate is used in calucalation of line impedances.

(a)

(b)

Figure 1. (a) Substrate Definition options of substrate types, (b) the definition of strapline used in this blog.

Define your stackup:

The stackup in Circuit is very similar to the stackup in HFSS 3D Layout. Please note that the definition of substrate is not automatically transferred to the stackup. The stackup needs to be defined by the user. Select the Schematic tab and from the top banner choose Stackup. Then define each layer. This stackup will be used in creating the layout and transferring it to HFSS 3D Layout.  Figure 2 shows the stackup used for the FR4 substrate that was defined in Figure 1(b).

Figure 2. Stackup definition that will be used to transfer the layout to HFSS 3D Layout.

Create the circuit:

Circuit provides a large selection of component libraries. To see the Component Libraries, click on View and check Component Libraries. In the Component Libraries window look for Distributed and expand it. Under this category you see different types of PCB structures. We will use Stripline library. Expanding Stripline library there are various categories, including Transmission Lines. We need Transmission Line Physical Length component, as we would like to use pieces of transmission line to create an ideal branch line coupler. You notice by hovering the cursor on the name of the component a small information windows shows the symbol and information about the component, alternatively you can right-click on the name of the component and choose “View Component Help” to get to the complete help page about the component. Once a component is selected and placed in the circuit it will also appear under the Project Components list at the bottom of the Component Libraries list. This provides a quick way to reuse them (Figure 3).

Figure 3. (a) Component Libraries, (b) Project Components and information window.

Let’s choose a physical length transmission line and place it on the schematic window. By double clicking on the symbol the Properties window opens and can be modified. Explicit values or parameters can be used to define the line properties.

Are you starting to calculate the line impedance to figure out the dimensions? Wait, there is a tool here that helps you do that. Click on TRL to open the line calculator. The line can be synthesized based on its impedance and electrical size by choosing the correct frequency and clicking on Synthesize (Figure 4). Using physical length transmission lines (50 and 35 ohms) and Tee lines and 4 ports I created an ideal branch line coupler (Figure 5). I ran a frequency analysis to make sure the circuit is working properly.

Before moving on to export the layout to HFSS 3D layout we can do one more step. To keep the substrate definition and reuse it layer, click on File->Save As Technology File. This would save the definition of stripline substrate in the personal library. Next step is to export the layout to HFSS 3D layout.

Figure 4. Properties and TRL windows.

Figure 5. Branch line coupler schematic.

Export to HFSS 3D Layout:

Under Schematic tab, click on Layout, or from the top menu choose Circuit->Layout Editor. Notice that this layout editor is very similar to the HFSS 3D Layout window. Click Ctrl+A, to select everything. Then choose Draw form the top banner and click on Align MW Ports (Figure 6), notice that other tools are also available under Draw, such as Sanitize Layout and Geometry Healing. You might need to do a bit more corrections and cleaning before exporting the layout. Before exporting the geometry, you can also check the HFSS Airbox using Layout->Draw HFSS Airbox.

Figure 6. Aligning ports.

You may change the orientation to Isometric for a better view of the box (Figure 7).

Figure 7. Layout editor in Isometric orientation, showing the HFSS airbox.

Make sure everything is still selected or select them with Ctrl+A, then under Edit, choose Copy to HFSS 3D Layout.  Now an HFSS 3D Layout design is created. Open the design. There might be a few things you like to change. Expand the ports, the name of the ports might have changed. You also note that the ports are of Gap type. You can select the port and in the Properties window, under HFSS click on Gap and choose the Wave port. Just note that the wave port cannot be internal to the design. You might need to adjust the air box size or create PEC port caps in HFSS later.

The second point to consider is about the parameters defined in Circuit. Remember that we defined W35 and W50 as the line widths in Circuit. The parameter are transferred but several local variables are also created based on them. For example click on the 50 ohm line. The width is now shown as a new parameter. You can see the complete list of parameters that are created by choosing HFSS 3D Layout->Design Parameters. Under the Parameters Default you still see W35 and W50, but moving to Local Variables tab you see the parameters created based on the Parameters Default.

Figure 8. Properties window.

Export to HFSS:

Any HFSS 3D Layout design can be exported to HFSS. Click on Analysis from the project three. Right-click and Add HFSS Solution Setup (Figure 9). There is no need to run this analysis. It just needs to be created. Right-click on the HFSS Setup that was just created, select Export->HFSS Model (Figure 10). Select the name and location for this file. Open this file and examine the model. Notice that the parameters are not transferred to HFSS model, this is because all parts of the model are imported (Figure 11). The default ports (Gap ports) appear as lumped port. If you changed the Gap ports to Wave ports in HFSS 3D Layout, it is now the time to add the PEC port caps or change the airbox to make sure ports are not internal to the model.

Figure 9. Adding HFSS solution setup.

Figure 10. Exporting the layout to an HFSS model.

Figure 11. HFSS model.

It is important to note that the type of analysis in Circuit is different than HFSS which will lead to slightly different result (Figure 12), which is expected and emphasizes the value of simulating structures in a full-wave field simulator like HFSS.

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Figure 12. (a) Branch-line coupler S parameters from Circuit model, (b) the imported HFSS branch-line coupler S parameters.

Conclusion

This was a short blog showing the workflow for importing PCB and planar designs from AEDT Circuit to HFSS 3D Layout and HFSS. The workflow is a good method to quickly create the HFSS model of a planar structure.

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

General Interface & Performance Updates in Ansys 2021 R1 – Webinar

Ansys 2021 R1 delivers significant improvements in simulation technology together with nearly unlimited computing power to help engineers across all industries reimagine product design and achieve product development goals that were previously thought to be impossible.

Ansys Mechanical delivers features to enable faster simulations, easier workflows, journaling, scripting and product integrations that offer more solver capabilities. Within this new release, interface and performance capabilities have been enhanced to offer greater ease of use and overall efficiency in nearly every circumstance. 

Join PADT’s Simulation Support Manager and Ansys expert Ted Harris, for an overview of what updates in this release best energize this tool, such as enhancements made to:

• Solution History

• Fluid Network Creation

• Circuits

• GPU & Solvers

• And much more

Register Here

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

High Frequency Updates in Ansys 2021 R1 – Webinar

Whether leveraging improved workflows or leading-edge capabilities with Ansys 2021 R1, teams are tackling design challenges head on, eliminating the need to make costly workflow tradeoffs, developing next-generation innovations with increased speed and significantly enhancing productivity, all in order to deliver high-quality products to market faster than ever.

When it comes to high frequency electromagnetics, Ansys 2021 R1 delivers a plethora of groundbreaking enhancements. Ansys HFSS Mesh Fusion enables simulation of large, never before possible electromagnetic systems with efficiency and scalability. This release also allows for encrypted 3D components supported in HFSS 3D Layout for PCBs, IC packages and IC designs to enable suppliers to share detailed 3D component designs for creating highly accurate simulations.

Join PADT’s Lead Electromagnetics Engineer and high frequency expert Michael Griesi for a presentation on updates made to the Ansys HF suite in the 2021 R1 release, including advancements for:

  • Electronics Desktop
  • HFSS
  • Circuits
  • EMIT
  • And Much More

Register Here

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

3D Printing Polymer Parts with Electrostatic Dissipative (ESD) Properties

Getting zapped by static electricity at the personal level is merely annoying; having your sensitive electronic equipment buzzed is another, highly destructive story.

Much as you’d like to send these components out into the world wearing their own little anti-static wristbands, that’s just not practical (and actually, not good enough*). During build and use, advanced electronics applications need true charge-dissipative protection that is inherent to their design and easy to achieve. However, the typical steps of painting or coating, covering with conductive tape, or wrapping with carbon-filled/aluminum-coated films incur both time and cost.

Electrostatic dissipative (ESD) polymer materials instead provide this kind of protection on a built-in basis, offering a moderately conductive “exit path” that naturally dissipates the charge build-up that can occur during normal operations. It also prevents powders, dust or fine particles from sticking to the surface. Whether the task is protecting circuit boards during transport and testing, or ensuring that the final product works as designed throughout its lifetime, ESD materials present low electrical resistance while offering the required mechanical, and often thermal and/or chemically-resistant properties.

ESD-safe fixture for testing a printed-circuit board, produced by 3D printing with Stratasys ABS-ESD7 material. (Image courtesy of Stratasys)

Combining ESD Behavior with 3D Printing

All the features that are appealing with 3D printing carry over when printing with ESD-enabled thermoplastics. You can print trays custom-configured to hold circuit-boards for in-process testing, print conformal fixtures that speed up sorting, and produce end-use structures for projects where static build-up is simply not allowed (think mission-critical aerospace applications).

Acrylonitrile butadiene styrene (ABS), that work-horse of the plastics industry, has been available as 3D printing filament for decades. Along the way, Stratasys and other vendors started offering this filament in a version filled with carbon particles that decrease the plastic’s inherent electrical resistance. Stratasys ABS-ESD7 runs on the Fortus 380, 400, 450 and 900 industrial systems, and soon will be available on the office-friendly F370 printer.

What kind of performance does ABS-ESD7 offer? When evaluating materials for ESD performance, the most important property is usually the surface resistance, measured in ohms. (This is not the same as surface resistivity, plus there’s also volume resistivity – see Note at end). Conductive materials – typically metals – have a surface resistance generally less than 103 ohms, insulators such as most plastics are rated at greater than 1012 ohms, and ESD materials fall in the mid-range, at 106 to 109 ohms.

Compared to standard ABS filament, ABS-ESD7 offers more than five orders of magnitude lower resistance, converting it from an insulator to a material that provides an effective static-discharge path to the outside world. Due to the inherent layered structure of FDM parts, the differences in properties between flat (XY) and vertical (ZX) build orientations produces a range of resistance values, with a target of 107 ohms, reflected in the product name of ABS-ESD7. Stratasys offers an excellent, easy-to-read FAQ paper about ABS-ESD7.

Printed-circuit board production tool, custom 3D-printed in Stratasys ABS-ESD7 material for built-in protection from electrostatic discharge during test and handling. (Image courtesy of Stratasys)

When ABS isn’t strong enough or won’t hold up to temperature extremes, engineers can turn to Stratasys’ ESD-enhanced polyetherketoneketone (PEKK), termed Antero 840CN03. Developed in 2016 and slated for full release in October 2019, this new filament expands the company’s Antero line of  high-temperature, chemically resistant formulations. The PEKK base material offers a high glass transition temperature (Tg 149C, compared to 108C for ABS-ESD7) while meeting stringent outgassing and cleanroom requirements. As with ABS-ESD7, the carbon-nanotube loading lowers electrical resistance values of Antero 840CN03 parts to the desirable “ESD safe” range of 106 to 109 ohm.

Setting up Parts for Printing with ESD-Enhanced Filament                                                            

Support structures in contact with part walls/surfaces can disturb the surface resistance behavior. To counter-act this condition for filament printing with any type of ESD material, users should perform a special calibration that makes the printer lay down slightly thinner-than-usual layers of support material. In Stratasys Insight software, this is currently accomplished by setting the Support Offset Thickness to -0.003; this decreases the support layers from 0.010 inches to 0.007 inches. In addition, supports should be removed (in Insight software) from holes that are smaller in diameter than 0.25 inches (6.35mm).

As more of these materials are developed, the software will be updated to automatically create supports with this process in mind.

ESD Applications for 3D Printing

Avionics boxes, fixtures for holding and transporting circuit boards, storage containers for fuel, and production-line conveyor systems are just a few examples of end-use applications of ESD-enabled materials. Coupled with the geometric freedom offered by 3D printing, three categories of manufacturing and operations are improved:

  • Protecting electronics from ESD damage (static shock)
  • Preventing fire/explosion (static spark)
  • Preserving equipment/product performance (static cling)

If you’re exploring how 3D printing with ESD-enhanced materials can help with your industrial challenge, contact our PADT Manufacturing group: get your questions answered, have some sample parts printed, and discover what filament is right for you.

PADT Inc. is a globally recognized provider of Numerical Simulation, Product Development and 3D Printing products and services. For more information on Insight, GrabCAD and Stratasys products, contact us at info@padtinc.com.

*Anti-static is a qualitative term and refers to something that prevents build-up of static, rather than dissipating what does occur


Surface Resistance, Surface Resistivity and Volume Resistivity

Surface resistance in ohms is a measurement to evaluate static-dissipative packaging materials.

Surface resistivity in ohms/square is used to evaluate insulative materials where high resistance characteristics are desirable. (Ref. https://www.evaluationengineering.com/home/article/13000514/the-difference-between-surface-resistance-and-surface-resistivity)

The standard for measuring surface resistance of ESD materials is EOS/ESD S11.11, released in 1993 by the ESD Association as an improvement over ASTM D-257 (the classic standard for evaluating insulators). Driving this need was the non-homogeneous structure of ESD materials (conductive material added to plastic), which had a different effect on testing parameters such as voltage or humidity,  than found with evaluating conductors.

Volume resistivity is yet a third possible measured electrical property, though again better suited for true conductors rather than ESD material. It depends on the area of the ohmeter’s electrodes and the thickness of the material sample. Units are ohm-cm or ohm-m.