Introduction:
Every year Ansys creates multiple updates to the different softwares. Sometimes these updates are quality of life improvements, sometimes fixes to prior bugs and/or errors, and sometimes they are general enhancements to the entire tool. Today we are going to present simulation benchmark information around a new beta feature in 2022 R2 called Parallel Mesh Refinement (PMR). We have created a microstrip differential pair created in HFSS and will be simulating it at multiple lengths in attempt to compare simulation times between using PMR and not using the new feature. Before we begin, we will show you where to find this new feature within the Electronics Desktop.
Where to find beta features:
In the design ribbon shown in figure 1, we can click on general options. This will open a dialog box found in figure 2. Within General go to “Desktop Configuration” and then at the bottom click on “Beta Options.” This will open a beta options selector with all the available beta options. For this blog we will be focusing on PMR only. Checking/Unchecking the box next to PMR will enable/disable it as shown in figure 3.
Figure 1. Finding General Options
Figure 2. General Options
Figure 3. Beta Options Selector
Simulation Setup:
For this simulation we have created a differential microstrip with an FR4 substrate. The conductors are copper, and the geometry is created for a differential impedance of 90-ohm. Figure 4 shows the cross section of the differential microstrip. We are using waveports set at each end of the microstrip with the same ground as reference. For the analysis setup we are using a broadband mesh with default settings, a low frequency of 1 MHz and a high frequency of 20 GHz, and a max delta S of 0.02. Figure 5 depicts the analysis setup used for each run. For the frequency sweep we are using an interpolating sweep with a sweep of 0-20GHz, and a default setting of 0.5% error tolerance. We are varying the length of the microstrip in order to increase the mesh counts and potential time of simulation. Table 1 depicts the different lengths used and figure 6 shows an example of the microstrip at a certain length.
Figure 4. Differential microstrip cross section
Figure 5. Analysis setup.
Run Number |
Length (Mils) |
1 |
1500 |
2 |
3000 |
3 |
3500 |
4 |
4000 |
5 |
4500 |
6 |
5000 |
7 |
5500 |
8 |
6000 |
Table 1. Length of each differential microstrip for each simulation
Figure 6. Example of differential microstrip length (6000 mils)
Simulation Results:
Simulation results are shown in table 2 while also being shown graphically in figure 7.
Run Number |
Length (mils) |
PMR Time (seconds) |
Without PMR Time (seconds) |
Approximate number of solved elements without PMR |
1 |
1500 |
299 |
455 |
10,000 |
2 |
3000 |
838 |
825 |
51,000 |
3 |
3500 |
1190 |
1182 |
73,000 |
4 |
4000 |
1060 |
1891 |
120,000 |
5 |
4500 |
2205 |
7289 |
360,000 |
6 |
5000 |
2337 |
1758 |
110,000 |
7 |
5500 |
2349 |
3121 |
180,000 |
8 |
6000 |
2112 |
4169 |
230,000 |
Table 2. Simulation Results
Figure 7. Results of simulation
Discussion:
The data shows that PMR almost always gives a benefit is nearly equal to a non-PMR run. There appears to be a significant benefit in solve time when mesh counts are higher than 100k elements and would expect for this to continue as mesh element size increases. It is worth noting that the writer’s intent was just comparing with a single, rather simple model. Additional investigation will need to be performed on more complex models with non-ideal geometry as well as port sizes that are greater than two. For now, this data provides some interesting insight into this new beta feature that could provide a simulation speed boost to an area (meshing) where it has been difficult to see speed increases in the past. The writers would also love to express interest in seeing how our customers results with this new feature and any feedback with PMR. We imagine that Ansys will continue to refine this beta feature for additional usage and are excited to see how this may improve simulation times for more complex models moving forward.
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