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by mindviews 3254 days ago
>Have you tried stripline as a benchmark?

No - just pulled the paper on it and put that on my to-do list. We've been focused on large problems recently and people seem happy to stick with scattering by spheres (PEC or dielectric) and comparison with the Mie solution. Way too much symmetry to serve as a comprehensive benchmark, but a decent way to compare computational efficiency. Our current benchmark run for a 100 wavelength diameter PEC sphere is 48 minutes on 256 CPU cores with 0.13% RMS error in the far field. We recently got 1.8% far field error for the 500 wavelength case on 300 cores in 17.8 hours. Our preliminary 1,000 wavelength numbers are very promising, too. No GPU/MIC or unusual hardware for those tests - all on a cluster of modern servers with Intel Xeon CPUs with 2-4 GB RAM per core.

Finding good benchmarks for sharp corners has been more challenging. The one we've been using for that is planewave scattering by a PEC cube and we test that the fields inside are 0 everywhere (including arbitrarily close to the surface at corners and edges).

Thanks for your other comments - geometry translation comes up often. Post-processing as you mentioned elsewhere is a common pain point, too, but solutions there seem to be pretty application/domain specific.

1 comments

Nice; Mie scrattering; I was explaining creeping waves with someone recently; cool stuff. I have not done too much with RCS or large structures. I'm mostly RF/Microwave circuits and antennas, though as I move into mmWave, electrically large antennas (both arrays and reflectors) will be come an issue.

Does your code handle lossy dielectrics?

Anyway to instantiate near-field excitation sources on large structures? That's one nice thing about CST; save the near field results from an FEM antenna simulation and instantiate them into a TLM simulation on a large structure.

A a side note, we had a new near field chamber installed, and the guy from Orbit/FR used to run several test ranges. Got on the topic of antenna standards (there really are not any, even standard gain horns). He developed some cylinder standards for scattering. They ship them around the world to verify ranges.

Yes to lossy dielectrics. The caveat being that right now we only have support for homogeneous materials - we have some thoughts on how to bring our methods to continuously varying materials, but that's still a research topic.

We started out focused on RCS problems for algorithm development and validation, but we're shifting to more antenna design and analysis (mounted antennas, installed performance, placement optimization). We have done near-field excitation of our own models on large structures, but usually our goal has been to maintain accuracy so our use case has us solve the driven antenna and the platform together in one go.