## 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.

## Defining Antenna Array Excitations with Nested-If Statements in HFSS

HFSS offers various methods to define array excitations. For a large array, you may take advantage of an option “Load from File” to load the magnitude and phase of each port. However, in many situations you may have specific cases of array excitation. For example, changing amplitude tapering or the phase variations that happens due to frequency change. In this blog we will look at using the “Edit Sources” method to change the magnitude and phase of each excitation. There are cases that might not be easily automated using a parametric sweep. If the array is relatively small and there are not many individual cases to examine you may set up the cases using “array parameters” and “nested-if”.

In the following example, I used nested-if statements to parameterize the excitations of the pre-built example “planar_flare_dipole_array”, which can be found by choosing File->Open Examples->HFSS->Antennas (Fig. 1) so you can follow along. The file was then saved as “planar_flare_dipole_array_if”. Then one project was copied to create two examples (Phase Variations, Amplitude Variations).

Fig. 1. Planar_flare_dipole_array with 5 antenna elements (HFSS pre-built example).

# Phase Variation for Selected Frequencies

In this example, I assumed there were three different frequencies that each had a set of coefficients for the phase shift. Therefore, three array parameters were created. Each array parameter has 5 elements, because the array has 5 excitations:

A1: [0, 0, 0, 0, 0]

A2: [0, 1, 2, 3, 4]

A3: [0, 2, 4, 6, 8]

Then 5 coefficients were created using a nested_if statement. “Freq” is one of built-in HFSS variables that refers to frequency. The simulation was setup for a discrete sweep of 3 frequencies (1.8, 1.9 and 2.0 GHz) (Fig. 2). The coefficients were defined as (Fig. 3):

E1: if(Freq==1.8GHz,A1[0],if(Freq==1.9GHz,A2[0],if(Freq==2.0GHz,A3[0],0)))

E2: if(Freq==1.8GHz,A1[1],if(Freq==1.9GHz,A2[1],if(Freq==2.0GHz,A3[1],0)))

E3: if(Freq==1.8GHz,A1[2],if(Freq==1.9GHz,A2[2],if(Freq==2.0GHz,A3[2],0)))

E4: if(Freq==1.8GHz,A1[3],if(Freq==1.9GHz,A2[3],if(Freq==2.0GHz,A3[3],0)))

E5: if(Freq==1.8GHz,A1[4],if(Freq==1.9GHz,A2[4],if(Freq==2.0GHz,A3[4],0)))

Please note that the last case is the default, so if frequency is none of the three frequencies that were given in the nested-if, the default phase coefficient is chosen (“0” in this case).

Fig. 2. Analysis Setup.

Fig. 3. Parameters definition for phase varaitioin case.

By selecting the menu item HFSS ->Fields->Edit Sources, I defined E1-E5 as coefficients for the phase shift. Note that phase_shift is a variable defined to control the phase, and E1-E5 are meant to be coefficients (Fig. 4):

Fig. 4. Edit sources using the defined variables.

The radiation pattern can now be plotted at each frequency for the phase shifts that were defined (A1 for 1.8 GHz, A2 for 1.9 GHz and A3 for 2.0 GHz) (Figs 5-6):

Fig. 5. Settings for radiation pattern plots.

Fig. 6. Radiation patten for phi=90 degrees and different frequencies, the variation of phase shifts shows how the main beam has shifted for each frequency.

# Amplitude Variation for Selected Cases

In the second example I created three cases that were controlled using the variable “CN”. CN is simply the case number with no units.

The variable definition was similar to the first case. I defined 3 array parameters and 5 coefficients. This time the coefficients were used for the Magnitude. The variable in the nested-if was CN. That means 3 cases and a default case were created. The default coefficient here was chosen as “1” (Figs. 7-8).

A1: [1, 1.5, 2, 1.5, 1]

A2: [1, 1, 1, 1, 1]

A3: [2, 1, 0, 1, 2]

E1: if(CN==1,A1[0],if(CN==2,A2[0],if(CN==3,A3[0],1)))*1W

E2: if(CN==1,A1[1],if(CN==2,A2[1],if(CN==3,A3[1],1)))*1W

E3: if(CN==1,A1[2],if(CN==2,A2[2],if(CN==3,A3[2],1)))*1W

E4: if(CN==1,A1[3],if(CN==2,A2[3],if(CN==3,A3[3],1)))*1W

E5: if(CN==1,A1[4],if(CN==2,A2[4],if(CN==3,A3[4],1)))*1W

Fig. 7. Parameters definition for amplitude varaitioin case.

Fig. 8. Exciation setting for amplitude variation case.

Notice that CN in the parametric definition has the value of “1”. To create the solution for all three cases I used a parametric sweep definition by selecting the menu item Optimetrics->Add->Parametric. In the Add/Edit Sweep I chose the variable “CN”, Start: 1, Stop:3, Step:1. Also, in the Options tab I chose to “Save Fields and Mesh” and “Copy geometrically equivalent meshes”, and “Solve with copied meshes only”. This selection helps not to redo the adaptive meshing as the geometry is not changed (Fig. 9). In plotting the patterns I could now choose the parameter CN and the results of plotting for CN=1, 2, and 3 is shown in Fig. 10. You can see how the tapering of amplitude has affected the side lobe level.

Fig. 9. Parameters definition for amplitude varaitioin case.

Fig. 10. Radiation patten for phi=90 degrees and different cases of amplitude tapering, the variation of amplitude tapering has caused chagne in the beamwidth and side lobe levels.

# Drawback

The drawback of this method is that array parameters are not post-processing variables. This means changing them will create the need to re-run the simulations. Therefore, it is needed that all the possible cases to be defined before running the simulation.

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

## Frequency Dependent Material Definition in ANSYS HFSS

Electromagnetic models, especially those covering a frequency bandwidth, require a frequency dependent definition of dielectric materials. Material definitions in ANSYS Electronics Desktop can include frequency dependent curves for use in tools such as HFSS and Q3D. However, there are 5 different models to choose from, so you may be asking: What’s the difference?

In this blog, I will cover each of the options in detail. At the end, I will also show how to activate the automatic setting for applying a frequency dependent model that satisfies the Kramers-Kronig conditions for causality and requires a single frequency definition.

# Background

Recalling that the dielectric properties of material are coming from the material’s polarization

where D is the electric flux density, E is the electric field intensity, and P is the polarization vector. The material polarization can be written as the convolution of a general dielectric response (pGDR) and the electric field intensity.

The dielectric polarization spectrum is characterized by three dispersion relaxation regions α, β, and γ for low (Hz), medium (KHz to MHz) and high frequencies (GHz and above). For example, in the case of human tissue, tissue permittivity increases and effective conductivity decreases with the increase in frequency [1].

Each of these regions can be modeled with a relaxation time constant

where τ is the relaxation time.

The well-known Debye expression can be found by use of spectral representation of complex permittivity (ε(ω)) and it is given as:

where ε is the permittivity at frequencies where ωτ>>1, εs is the permittivity at ωτ>>1, and j2=-1. The magnitude of the dispersion is ∆ε = εs.

The multiple pole Debye dispersion equation has also been used to characterize dispersive dielectric properties [2]

In particular, the complexity of the structure and composition of biological materials may cause that each dispersion region be broadened by multiple combinations. In that case a distribution parameter is introduced and the Debye model is modified to what is known as Cole-Cole model

where αn, the distribution parameter, is a measure of broadening of the dispersion.

Gabriel et. al [3] measured a number of human tissues in the range of 10 Hz – 100 GHz at the body temperature (37℃). This data is freely available to the public by IFAC [4].

# Frequency Dependent Material Definition in HFSS and Q3D

In HFSS you can assign conductivity either directly as bulk conductivity, or as a loss tangent. This provides flexibility, but you should only provide the loss once. The solver uses the loss values just as they are entered.

To define a user-defined material choose Tools->Edit Libraries->Materials (Fig. 2). In Edit Libraries window either find your material from the library or choose “Add Material”.

To add frequency dependence information, choose “Set Frequency Dependency” from the “View/Edit Material” window, this will open “Frequency Dependent Material Setup Option” that provides five different ways of defining materials properties (Fig. 3).

Before choosing a method of defining the material please note [5]:

• The Piecewise Linear and Frequency Dependent Data Points models apply to both the electric and magnetic properties of the material. However, they do not guarantee that the material satisfies causality conditions, and so they should only be used for frequency-domain applications.
• The Debye, Multipole Debye and Djordjevic-Sarkar models apply only to the electrical properties of dielectric materials. These models satisfy the Kramers-Kronig conditions for causality, and so are preferred for applications (such as TDR or Full-Wave SPICE) where time-domain results are needed. They also include an automatic Djordjevic-Sarkar model to ensure causal solutions when solving frequency sweeps for simple constant material properties.
• HFSS and Q3D can interpolate the property’s values at the desired frequencies during solution generation.

Piecewise Linear

This option is the simplest way to define frequency dependence. It divides the frequency band into three regions. Therefore, two frequencies are needed as input. Lower Frequency and Upper Frequency, and for each frequency Relative Permittivity, Relative Permeability, Dielectric Loss Tangent, and Magnetic Loss Tangent are entered as the input. Between these corner frequencies, both HFSS and Q3D linearly interpolate the material properties; above and below the corner frequencies, HFSS and Q3D extrapolate the property values as constants (Fig. 4).

Once these values are entered, 4 different data sets are created (\$ds_epsr1, \$ds_mur1, \$ds_tande1, \$ds_tandm1). These data sets now can be edited. To do so choose Project ->Data sets, and choose the data set you like to edit and click Edit (Fig. 5). This data set can be modified with additional points if desired (Fig. 6).

Frequency Dependent

Frequency Dependent material definition is similar to Piecewise Linear method, with one difference. After selecting this option, Enter Frequency Dependent Data Point opens that gives the user the option to use which material property is defined as a dataset, and for each one of them a dataset should be defined. The datasets can be defined ahead of time or on-the-fly. Any number of data points may be entered. There is also the option of importing or editing frequency dependent data sets for each material property (Fig. 7).

Djordjevic-Sarkar

This model was developed initially for FR-4, commonly used in printed circuit boards and packages [6]. In fact, it uses an infinite distribution of poles to model the frequency response, and in particular the nearly constant loss tangent, of these materials.

where ε is the permittivity at very high frequency,  is the conductivity at low (DC) frequency,  j2=-1, ωA is the lower angular frequency (below this frequency permittivity approaches its DC value), ωB is the upper angular frequency (above this frequency permittivity quickly approaches its high-frequency permittivity). The magnitude of the dispersion is ∆ε = εs-ε∞.

Both HFSS and Q3D allow the user to enter the relative permittivity and loss tangent at a single measurement frequency. The relative permittivity and conductivity at DC may optionally be entered. Writing permittivity in the form of complex permittivity [7]

Therefore, at the measurement frequency one can separate real and imaginary parts

where

Therefore, the parameters of Djordjevic-Sarkar can be extracted, if the DC conductivity is known

If DC conductivity is not known, then a heuristic approximation is De = 10 εtan δ1.

The window shown in Fig. 8 is to enter the measurement values.

Debye Model

As explained in the background section single pole Debye model is a good approximation of lossy dispersive dielectric materials within a limited range of frequency. In some materials, up to about a 10 GHz limit, ion and dipole polarization dominate and a single pole Debye model is adequate.

The Debye parameters can be calculated from the two measurements [7]

Both HFSS and Q3D allow you to specify upper and lower measurement frequencies, and the loss tangent and relative permittivity values at these frequencies. You may optionally enter the permittivity at high frequency, the DC conductivity, and a constant relative permeability (Fig. 9).

Multipole Debye Model

For Multipole Debye Model multiple frequency measurements are required. The input window provides entry points for the data of relative permittivity and loss tangent versus frequency. Based on this data the software dynamically generates frequency dependent expressions for relative permittivity and loss tangent through the Multipole Debye Model. The input dialog plots these expressions together with your input data through the linear interpolations (Fig. 10).

## Cole Cole Material Model

The Cole Cole Model is not an option in the material definition, however, it is possible to generate the frequency dependent datasets and use Frequency Dependent option to upload these values. In fact ANSYS Human Body Models are built based on the data from IFAC database and Frequency Dependent option.

## Visualization

Frequency-dependent properties can be plotted in a few different ways. In View/Edit Material dialog right-click and choose View Property vs. Frequency. In addition, the dialogs for each of the frequency dependent material setup options contain plots displaying frequency dependence of the properties.

You can also double-click the material property name to view the plot.

## Automatically use causal materials

As mentioned at the beginning, there is a simple automatic method for applying a frequency dependent model in HFSS. Select the menu item HFSS->Design Setting, and check the box next to Automatically use casual materials under Lossy Dielectrics tab.

This option will automatically apply the Djordjevic-Sarkar model described above to objects with constant material permittivity greater than 1 and dielectric loss tangent greater than 0. Keep in mind, not only is this feature simple to use, but the Djordjevic-Sarkar model satisfies the Kramers-Kronig conditions for causality which is particularly preferred for wideband applications and where time-domain results will also be needed. Please note that if the assigned material is already frequency dependent, automatic creation of frequency dependent lossy materials is ignored.

If you would like more information or have any questions about ANSYS products please email info@padtinc.com

# References

• D.T. Price, MEMS and electrical impedance spectroscopy (EIS) for non-invasive measurement of cells, in MEMS for Biomedical Applications, 2012, https://www.sciencedirect.com/topics/materials-science/electrical-impedance
• W. D. Hurt, “Multiterm Debye dispersion relations for permittivity of muscle,” IEEE Trans. Biomed. Eng, vol. 32, pp. 60-64, 1985.
• S. Gabriel, R. W. Lau, and C. Gabriel. “The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues.” Physics in Medicine & Biology, vol. 41, no. 11, pp. 2271, 1996.
• Dielectric Properties of Body Tissues in the Frequency Range 10 Hz – 100 GHz, http://niremf.ifac.cnr.it/tissprop/.
• ANSYS HFSS Online Help, Nov. 2013, Assigning Materials.
• A. R. Djordjevic, R. D. Biljic, V. D. Likar-Smiljani, and T. K. Sarkar, “Wideband frequency-domain characterization of FR-4 and time-domain causality,” IEEE Trans. on Electromagnetic Compatibility, vol. 43, no. 4, p. 662-667, Nov. 2001.
• ANSYS HFSS Online Help, 2019, Materials Technical Notes.

# Useful Links

Piecewise Linear Input

Debye Model Input

Multipole Debye Model Input

Djordjevic-Sarkar

Enter Frequency Dependent Data Points

## Using ANSYS HPC or ANSYS HPC Pack Licenses in ANSYS Electronics Desktop (Maxwell or HFSS)

Taking advantage of HPC can dramatically speed up solutions for electronics simulations.  Depending on whether you have ANSYS HPC licenses or ANSYS HPC Pack licenses, a different setting needs to be made in the HPC options, as shown here.

In Electronics Desktop, we click Tools > Options > HPC and Analysis Options:

For ANSYS HPC licenses, we set the option to “Pool”.

For ANSYS HPC Pack licenses, we set the option to “Pack”.

With ANSYS HPC licenses, each license task enables an additional core for solving.  At release 19, 4 cores are enabled with standard licensing, so adding 8 ANSYS HPC tasks enables solving on 12 cores.  With HPC Pack licenses, the first task enables an additional 8 cores, while a second task enables 8×4 or an additional 32 cores, etc.  For more information, see the ANSYS documentation on HPC licensing.

## IEEE Day 2017: Smart Antennas for IoT and 5G

IEEE Day celebrates the first time in history when engineers worldwide and IEEE members gathered to share their technical ideas in 1884. Events were held around the world by 846 IEEE Chapters this year. So, to celebrate, I attended a joint chapter meeting in at The Museum of Flight in Seattle with technical presentations focused on “Smart Antennas for IoT and 5G”. There were approximately 60 in attendance, so assuming this was the average attendance globally results in over 50,000 engineers celebrating IEEE Day worldwide!

The Seattle seminar featured three speakers that spanned theory, design, test, integration, and application of smart antennas. There was much discussion about the complexity and challenges of meeting the ambitious goals of 5G, which extend beyond mobile broadband data access. Some key objectives of 5G are to increase capacity, increase data rates, reduce latency, increase availability, and improve spectral and energy efficiency by 2020. A critical technology behind achieving these goals is beamforming antenna arrays, which were at the forefront of each presentation.

Anil Kumar from Boeing focused on the application of mmWave technology on aircraft. Test data was used to analyze EM radiation leakage through coated and uncoated aircraft windows. However, since existing regulations don’t consider the increased path loss associated with such high frequencies, the integration of 5G wireless applications may be restricted or delayed. Beyond this regulatory challenge, Anil discussed how multipath reflectors and absorbers will present significant challenges to successful integration inside the cabin. Although testing is always required for validation, designing the layout of the onboard transceivers may be impractical to optimize without an asymptotic EM simulation tool that can account for creeping waves, diffraction, and multi-bounce.

Considering the test and measurement perspective, Jari Vikstedt from ETS-Lindgren focused on the challenges of testing smart antenna systems. Smart or adaptive antenna systems will not likely perform the same in an anechoic chamber test as they would in real systems. Of particular difficulty, radiation null placement is just as critical as beam placement. This poses a difficult challenge to the number and location of probes in a test environment. Not only would a large number of probes become impractical, there is significant shadowing at mmWave frequencies which can negatively impact the measurement. Furthermore, compact ranges can significantly impact testing and line of sight measurements become particularly challenging. While not a purely test-oriented observation, this lead to considering the challenge of tower hand off. If a handset and tower use beamforming to maintain a link, if is difficult for an approaching tower to even sense the handset to negotiate the hand-off.

In contrast, if the handset was continuously scanning, the approaching tower could be sensed to negotiate the hand-off before the link is jeopardized.

The keynote speaker, who also traveled from Phoenix to Seattle, was ASU Professor Dr. Constantine Balanis. Dr. Balanis opened his presentation by making a distinction between conventional “dumb antennas” and “smart antennas”. In reality, there are no smart antennas, but instead smart antenna systems. This is a critical point from an engineering perspective since it highlights the complexity and challenge of designing modern communication systems. The focus of his presentation was using an adaptive system to steer null points in addition to the beam in an antenna array using a least mean square (LMS) algorithm. He began with a simple linear patch array with fixed uniform amplitude weights, since an analytic solution was practical and could be used to validate a simulation setup. However, once the simulation results were verified for confidence, designing a more complex array with weighted amplitudes accompanying the element phase shift was only practical through simulation. While beam steering will create a device centric system by targeting individual users on massive multiple input multiple output (MIMO) networks, null steering can improve efficiency by minimizing interference to other devices.

Whether spatial processing is truly the “last frontier in the battle for cellular system capacity”, 5G technology will most certainly usher in a new era of high capacity, high speed, efficient, and ubiquitous means of communication. If you would like to learn more about how PADT approaches antenna simulation, you can read about it here and contact us directly at info@padtinc.com.

## Parameterizing Solid Models for ANSYS HFSS

ANSYS HFSS features an integrated “history-based modeler”. This means that an object’s final shape is dependent on each and every operation performed on that object. History-based modelers are a perfect choice for analysis since they naturally support parameterization for design exploration and optimization. However, editing imported solid 3D Mechanical CAD (or MCAD) models can sometimes be challenging with a history-based modeler since there are no imported parameters, the order of operation is important, and operational dependencies can sometimes lead to logic errors. Conversely, direct modelers are not bound by previous operations which can offer more freedom to edit geometry in any order without historic logic errors. This makes direct modelers a popular choice for CAD software but, since dependencies are not maintained, they are not typically the natural choice for parametric analysis. If only there was a way to leverage the best of both worlds… Well, with ANSYS, there is a way.

As discussed in a previous blog post, since the release of ANSYS 18.1, ANSYS SpaceClaim Direct Modeler (SCDM) and the MCAD translator used to import geometry from third-party CAD tools are now packaged together. The post also covered a few simple procedures to import and prepare a solid model for electromagnetic analysis. However, this blog post will demonstrate how to define parameters in SCDM, directly link the model in SCDM to HFSS, and drive a parametric sweep from HFSS. This link unites the geometric flexibility of a direct modeler to the parametric flexibility of a history-based modeler.

You can download a copy of this model here to follow along. If you need access to SCDM, you can contact us at info@padtinc.com. It’s also worth noting that the processes discussed throughout this article work the same for HFSS-IE, Q3D, and Maxwell designs as well.

[1] To begin, open ANSYS SpaceClaim and select File > Open to import the step file.

[2] Split the patch antenna and reference plane from the dielectric. Click here for steps to splitting geometry. Notice the objects can be renamed and colors can be changed under the Display tab.

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[1] Click and hold the center mouse button to rotate the model, zoom into the microstrip feed using the mouse scroll, then select the side of the trace.

[2] Rotate to the other side of the microstrip feed, hold the Ctrl key, and select the other side of the trace. Note the distance between the faces is shown as 3mm in the Status Bar at the bottom of the screen, which is the initial trace width.

[3] Select Design > Edit > Pull and select No merge under Options – Pull.

[4] Click the yellow arrow in the model, and drag the side of the trace. Notice how both faces move in or out to change the trace width. After releasing the mouse, a P will appear next to the measurement box. Click this P to create a parameter.

[5] Select the Groups panel under the Structure tree. Change “Group1” to “traceWidth” and reset the Ruler dimension to 0mm. Then, save the project as UWB_Patch_Antenna_PCB.scdoc and leave SCDM open.

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[1] Open ANSYS Electronics Desktop (AEDT), insert a new HFSS Design, and select the menu item Modeler > SpaceClaim Link > Connect to Active Session… Notice that there is an option to browse and open any SCDM project if the session is not currently active (or open).

[2] Select the active UWB_Patch_Antenna_PCB session and click Connect.

[3] The geometry from SCDM is automatically imported into HFSS.

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[1] Double-click the SpaceClaim1 model in the HFSS modeler tree and select the Parameters tab in the pop-up dialogue box. Notice the SCDM parameter can now be controlled within HFSS. Change the Value of traceWidth to SCDM_traceWidth to create a local variable and set SCDM_traceWidth equal to -1mm. Then click OK. Notice a lightning bolt over the SpaceClaim1 model to indicate changes have been made.

[2] Right-click SpaceClaim1 in the modeler tree and select Send Parameters and Generate.

[3] Notice how the HFSS geometry reflects the changes.

[4] Notice how the SCDM also reflects the changes. In practice, it is generally recommended to browse to unopen SCDM projects (rather than connecting to an active session) to avoid accidentally editing the same geometry in two places.

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At this point, not only can the geometry in SCDM be controlled by variables in HFSS, but a parametric analysis can now be performed on geometry within a direct modeler. The best of both worlds!

Use the typical steps within HFSS to setup a parametric sweep or optimization. When performing a parametric analysis, the geometry will automatically update the link between HFSS and SCDM, so step [2] above does not need to be performed manually. Be sure to follow the typical HFSS setup procedures such as assigning materials, defining ports and boundaries, and creating a solution setup before solving.

Here are some additional pro-tips:

1. Create local variables in HFSS that can be used for both local and linked geometry. For example, create a variable in HFSS for traceWidth = 3mm (which was the previously noted width). Define SCDM_traceWidth = (traceWidth-3mm)/2. Now the port width can scale with the trace width.

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1. Link to multiple SCDM projects. Either move and rotate parts as needed or create a separate coordinate system for each component. For example, link an SMA end connector to the same HFSS project to analyze both components. Notice that each component has variables and the substrate thickness changes both SCDM projects.

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1. Design other objects in the native HFSS history-based modeler that are dependent on the SCDM design variables. For example, the void in an enclosure could be a function of SCDM_dielectricHeight. Notice that the enclosure void is dependent on the SCDM dielectric height.

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## All Things ANSYS EP002: We talk about HFSS and Files Storage and Management with EKM

 Published on: August 14, 2017 With: Ahmed Fayed, Michael Griesi, Joe Woodward, Eric Miller Description: In our second try at a podcast we sit down with Michael, our inhouse HFSS expert, to talk about what HFSS is and how it can be used.  We also had the oportunity to have Ahmed join us from PADT’s IT team to talk about dealing with file storage when you use ANSYS products. We focused on how we use ANSYS EKM to get a handle on all of them.  This episode also includes news and our first ever commercial break. Listen: Subscribe:

## Importing and Splitting Solid Models for ANSYS HFSS 18.0

Importing solid 3D Mechanical CAD (or MCAD) models into ANSYS HFSS has always been and remains to be a fairly simple process. After opening ANSYS Electronics Desktop and creating an HFSS design, from the menu bar, select Modeler > Import. A dialog box will open to navigate to and directly open the model.

The CAD will automatically be translated and loaded into the HFSS 3D Modeler. If the geometry is correct and does not require any editing, the import process is complete and analysis can begin! However, if there are any errors with the geometry, there is excessive or invalid detail, or if it’s not organized into separate bodies conducive for electromagnetic analysis, you may soon realize that the editing capability is limited to scaling, reorienting, or Boolean operations. This approach can be particularly troublesome when portions of the model (or all of the model) which consist of different materials are not split into different objects. For example, notice the outer conductor, inner conductor, and dielectric of the imported SMA below are all one solid object.

Unless you’re lucky enough to work with the creator of the CAD, you will need to find a way to split this model into the inner and outer conductors, and the dielectric. However, since the release of ANSYS R18.1, the power of SpaceClaim Direct Modeler (SCDM) and the MCAD translator will be packaged together. The good news is, the process described above will continue to work. The better news is, SCDM offers new capabilities to directly edit or clean imported geometry. So, here are a few simple steps to quickly split this SMA connector using SCDM. You can download a copy of this model here to follow along. If you need access to SCDM, you can contact us at info@padtinc.com. It’s worth noting, at this point, that the processes discussed throughout this article work the same for HFSS-IE, Q3D, and Maxwell designs as well.

[1] First, after opening ANSYS SpaceClaim, the step file can be imported through the menu File > Open or by simply dragging and dropping the file into the SCDM window. [2] To separate the dielectric from the outer conductor, select Design > Intersect > Split Body. [3] Click and hold the center mouse button to rotate the model so the boundary between the dielectric and outer conductor is visible. Hold the Ctrl key and click the center mouse button to pan, and use the center mouse scroll to zoom in and out. Finally, press ‘z’ on the keyboard to fit the view window. [4] When positioned, click on the object to split (in this case it is the entire model). [5] Then, click on the face which defines the boundary between the dielectric and outer conductor. [6] Finally, press the Esc key. The first split is done!

Repeat the Split Body process to separate the center conductor from the dielectric. Notice under the structure tree that there are now three separate objects.

The split body function is also useful to simplify a structure for analysis. For example, the female side of the SMA could be simplified as a solid center conductor. [1] Reposition the connector to view the female side. [2]-[3] Control the visibility of each body with the object’s checkbox in the structure tree. [4] Measure the length of the female side by pressing the letter ‘e’ on the keyboard and selecting the top edge (note the line length of 2.95mm for later). [5] Then, repeat the Split Body process to split the center conductor at the boundary between the male and female sides. [6]-[7] However, rather than pressing the Esc key, click on the female receiver to automatically remove the body.

[1] To extend the center pin to its original length, select Design > Edit > Pull. [2] Click on the face where the female side was originally attached and select the Up To option. [3] Type in the previously measured length of 2.95mm. [4] Finally, press Enter (press Esc 3x to exit the Pull command).

Repeat the Split Body and Pull processes until the model has been divided into different bodies for each material type and is sufficiently simplified.

Once the model is ready, select File > Save As to save the geometry as the preferred format. Perhaps the most familiar approach to HFSS users would be to save the new model as a STEP file, then to import the model into HFSS as described in the first paragraph.

## Jet Engines to Golf Clubs – Phoenix Area ANSYS Users Share their Stories

There is nothing better than seeing the powerful and interesting way that other engineers are using the same tools you use.  That is why ANSYS, Inc. and PADT teamed up on Thursday to hold an “ANSYS Arizona Innovation Conference”  at ASU SkySong where users could come to share and learn.

The day kicked off with Andy Bauer from ANSYS welcoming everyone and giving them an update on the company and some general overarching direction for the technology.  Then Samir Rida from Honeywell Aerospace gave a fantastic keynote sharing how simulation drive the design of their turbine engines.  As a former turbine engine guy, I found it fascinating and exciting to see how accurate and detailed their modeling is.

Next up was my talk on the Past, Present, and Future of simulation for product development.  The point of the presentation was to take a step back and really think about what simulation is, what we have been doing, and what it needs to look at in the future.  We all sort of agreed that we wanted voice activation and artificial intelligence built in now.  If you are interested, you can find my presentation here: padt-ansys-innovation-az-2016.pdf.

After a short break ANSYS’s Sara Louie launched into a discussion on some of the new Antenna Systems modeling capabilities, simulating multiple physics and large domains with ANSYS products.  The ability to model the entire interaction of an antenna including large environments was fascinating.

Lunchtime discussions focused on the presentations in the morning as well as people sharing what they were working on.

The afternoon started with a review by Hoang Vinh of ANSYS of the ANSYS AIM product. This was followed by customer presentations. Both Galtronics and ON Semiconductor shared how they drive the design of their RF systems with ANSYS HFSS and related tools.  Then Nammo Talley shared how they incorporated simulation into their design process and then showed an example of a projectile redesign from a shoulder launched rocket that was driven by simulation in ANSYS CFX.  They had the added advantage of being able to show something that blows up, always a crowd pleaser.

Another break was followed by a great look at how Ping used CFD to improve the design of one of their drivers.  They used simulation to understand the drag on the head through an entire swing and then add aerodynamic features that improved the performance of the club significantly. Much of the work is actually featured in an ANSYS Advantage article.

We wrapped things up with an in depth technical look at Shock and Vibration Analysis using ANSYS Mechanical and Multiphysics PCB Analysis with the full ANSYS product suite.

The best part of the event was seeing how all the different physics in ANSYS products were being used and applied in different industries.  WE hope to have similar events int he future so make sure you sign up for our mailings, the “ANSYS – Software Information & Seminars” list will keep you in the loop.

## 10x with ANSYS 17.0 – Get an Order of Magnitude Impact

The ANSYS 17.0 release improves the impact of driving design with simulation by a factor of 10.  This 10x  jump is across physics and delivers real step-change enhancements in how simulation is done or the improvements that can be realized in products.

Unless you were disconnected from the simulation world last week you should be aware of the fact that ANSYS, Inc released their latest version of the entire product suite.  We wanted to let the initial announcement get out there and spread the word, then come back and talk a little about the details.  This blog post is the start of a what should be a long line of discussions on how you can realize 10x impact from your investment in ANSYS tools.

As you may have noticed, the theme for this release is 10x. A 10x improvement in speed, efficiency, capability, and impact.  Watch this short video to get an idea of what we are talking about.

## Where is the Meat?

We are already seeing this type of improvement here at PADT and with our customers. There is some great stuff in this release that delivers some real game-changing efficiency and/or capability.  That is fine and dandy, but how is this 10x achieved.  There are a lot of little changes and enhancements, but they can mostly be summed up with the following four things:

### Tighter Integration of Multiphysics

Having the best in breed simulation tools is worth a lot, and the ANSYS suite leads in almost every physics.  But real power comes when these products can easily work together.  At ANSYS 17.0 almost all of the various tools that ANSYS, Inc. has written or acquired can be used together. Multiphysics simulation allows you to remove assumption and approximations and get a more accurate simulation of your products.

And Multiphysics is about more than doing bi-directional simulation, which ANSYS is very good at. It is about being able to transfer loads, properties, and even geometry between different software tools. It is about being able to look at your full design space across multiple physics and getting more accurate answers in less time.  You can take heat loads generated in ANSYS HFSS and use them in ANSYS Mechanical or ANSYS FLUENT.  You can take the temperatures from ANSYS FLUENT and use them with ANSYS SiWave.  And you can run a full bidirectional fluid-solid model with all the bells and whistles and without the hassles of hooking together other packages.

To top it all off, the system level modeler ANSYS Simplorer has been improved and integrated further, allowing for true system level Multiphysics virtual prototyping of your entire system.  One of the changes we are most excited about is full support for Modelica models – allowing you to stay in Simplorer to model your entire system.

### Improved Usability

Speed is always good, and we have come to expect 10%-30% increases in productivity at almost every release. A new feature here, a new module there. This time the developers went a lot further and across the product lines.

The closer integration of ANSYS SpaceClaim really delivers on a 10x or better speedup for geometry creation and cleanup when compared to other methods. We love SpaceClaim here at PADT and have been using it for some time.  Version 17 is not only integrated tighter, it also introduces scripting that allows users to take processes they have automated in older and clunker interfaces into this new more powerful tool.

One of our other favorites is the new interface in ANSYS Fluent, just making things faster and easier. More capability in the ANSYS Customization Toolkit (ACT) also allows users to get 10x or better improvements in productivity.  And for those who work with electronics, a host of ECAD geometry import tools are making that whole process an order of magnitude faster.

### Industry Specific Workflows

Many of the past releases have been focused on establishing underlying technology, integration, and adding features. This has all paid off and at 17.0 we are starting to see some industry specific workflows that get models done faster and produce more accurate results.

The workflow for semiconductor packaging, the Chip Package System or CPS, is the best example of this. Here is a video showing how power integrity, signal integrity, thermal modeling, and integration across tools:

A similar effort was released in Turbomachinary with improvements to advanced blade row simulation, meshing, and HPC performance.

### Overall Capability Enhancements

A large portion of the improvements at 17.0 are made up of relatively small enhancements that add up to so big benefits.  The largest development team in simulation has not been sitting around for a year, they have been hard at work adding and improving functionality.  We will cover a lot of these in coming posts, but some of our favorites are:

1. Improvements to distributed solving in ANSYS Mechanical that show good scaling on dozens of cores
2. Enhancements to ACT allowing for greater automation in ANSYS Mechanical
3. ACT is now available to automate your CFD processes
4. Significant improvements in meshing robustness, accuracy and speed (If you are using that other CFD package because of meshing, its time to look at ANSYS Fluent again)
5. Fracture mechanics
6. ECAD import in electromagnetic, fluids, and mechanical products.
7. A new solver in ANSYS Maxwell that solves more than 10x faster for transient runs
8. ANSYS AIM just keeps getting more functions and easier to use
9. A pile of SpaceClaim new and improved features that greatly speed up geometry repair and modification
10. Improved rigid body dynamics in ANSYS Mechanical

## More to Come

And a ton more. It may take us all of the time we have before ANSYS 18.0 comes out before we have a chance to go over in The Focus all of the great new stuff.  But we will be giving a try in the coming weeks and months. ANSYS, Inc. will be hosting some great webinars as well.

If you see something that interests you or something you would like to see that was not there, shoot us an email at support@padtinc.com or call 480.813.4884.

## Activating Hyperdrive in ANSYS Simulations

With PADT and the rest of the world getting ready to pile into dark rooms to watch a saga that we’ve been waiting for 10 years to see, I figured I’d take this opportunity to address a common, yet simple, question that we get:

“How do I turn on HPC to use multiple cores when running an analysis?”

For those that don’t know, ANSYS spends a significant amount of resources into making the various solvers it has utilize multiple CPU processors more efficiently than before.  By default, depending on the solver, you are able to use between 1-2 cores without needing HPC licenses.

With the utilization of HPC licenses, users can unlock hyperdrive in ANSYS.  If you are equipped with HPC licenses it’s just a matter of where to look for each of the ANSYS products to activate it.

## ANSYS Mechanical

Whether or not you are performing a structural, thermal or explicit simulation the process to activate multiple cores is identical.

1. Go to Tools > Solve Process Settings
2. The Solve Process Settings Window will pop up
3. Click on Advanced to open up the Advanced Settings window
4. You will see an option for Max number of utilized cores
5. Simply change the value to your desired core count
6. You will see below an option to allow for GPU acceleration (if your computer is equipped with the appropriate hardware)
7. Select the GPU type from the dropdown and choose how many GPUs you want to utilize
8. Click Ok and close

### Distributed Solve in ANSYS Mechanical

One other thing you’ll notice in the Advanced Settings Window is the option to turn “Distributed” On or Off using the checkbox.

In many cases Distributing a solution can be significantly faster than the opposite (Shared Memory Parallel).  It requires that MPI be configured properly (PADT can help guide you through those steps).  Please see this article by Eric Miller that references GPU usage and Distributed solve in ANSYS Mechanical

## ANSYS Fluent

Whether launching Fluent through Workbench or standalone you will first see the Fluent Launcher window.  It has several options regarding the project.

1. Under the Processing Options you will see 2 options: Serial and Parallel
2. Simply select Parallel and you will see 2 new dropdowns
3. The first dropdown lets you select the number of processes (equal to the number of cores) to use in not only during Fluent’s calculations but also during pre-processing as well

## ANSYS CFX

For CFX simulations through Workbench, the option to activate HPC exists in the Solution Manager

1. Open the CFX Solver Manager
2. You will see a dropdown for Run Mode
3. Rather than the default “Serial” option choose from one of the available “Parallel” options.
4. For example, if running on the same machine select Platform MPI Local Parallel
5. Once selected in the section below you will see the name of the computer and a column called Partitions
6. Simply type the desired number of cores under the Partitions column and then either click “Save Settings” or “Start Run”

## ANSYS Electronics Desktop/HFSS/Maxwell

Regardless of which electromagnetic solver you are using: HFSS or Maxwell you can access the ability to change the number of cores by going to the HPC and Analysis Options.

1. Go to Tools > Options > HPC and Analysis Options.
2. In the window that pops up you will see a summary of the HPC configuration
3. Click on Edit and you will see a column for Tasks and a column for Cores.
4. Tasks relate to job distribution utilizing Optimetrics and DSO licenses
5. To simply increase the number of cores you want to run the simulation on, change the cores column to your desired value
6. Click OK on all windows

There you have it.  That’s how easy it is to turn on Hyperdrive in the flagship ANSYS products to advance your simulations and get to your endpoint faster than before.

If you have any questions or would like to discuss the possibility of upgrading your ship with Hyperdrive (HPC capabilities) please feel free to call us at 1-800-293-PADT or email us at support@padtinc.com.