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Show HN: Open-Source Software for Designing 3D-Printable Luneburg Lenses for RF (github.com)

73 points by jboirazian ↗ HN
Hi HN community,

I’m excited to share my project, LuneForge, an open-source tool currently in development that aims to simplify the design of Luneburg lenses specifically for radio frequency (RF) applications. Luneburg lenses are unique gradient-index lenses that focus RF signals effectively, making them valuable in various RF and antenna systems aimed for military and automotive industry.

Key Features:

Customizable Designs: Easily adjust parameters to tailor lens designs to specific RF needs.

User-Friendly Interface: Designed to be accessible for both RF professionals and hobbyists.

3D-Printing Optimization: Models are optimized for SLA 3D printing, ensuring precise and high-quality lenses.

Community-Driven: We’re building a community of RF enthusiasts and professionals to contribute, share knowledge, and push the boundaries of RF lens design.

I’d love to hear your feedback, suggestions, or ideas for new features. Feel free to check out the repository [ https://github.com/jboirazian/LuneForge ]

37 comments

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abetusk
You say this is open source but I don't see a license on it. Did you mean source available?
jboirazian
Hi! Sorry something might have gone wrong and forgot to add it to the repo.

Its a standard MIT Licence

abetusk
Awesome!

Here's my feedback from an initial rough pass:

* Provide some references for what a Luneburg lens is. Not everyone will have the same context as you and will need to look up what a Luneburg lens is (like I did), distracting from what your contribution is. Once the context is provided, articulate clearly what your contribution is (which maybe you've already done).

* Provide example pictures of the lensing effect on different (input?) waveforms. The Wikipedia article has some pictures [0] [1], and other references [2], that, while needing context to understand, at least get some of the point across and provide an anchor point for further investigation.

* Have an online demo so that people can immediately play around with it

* Provide a quickstart section that shows how to start their own instance, including the call to firefox/chrome to open the web browser to the appropriate page

* I don't know what's up with that video but it's having a hard time playing back. Further, it takes at least 12 seconds of seeing input field filling and "progress bar" like animations before anything is actually displayed. The payoff should be within 5s (preferably less) of the start of the video to communicate what you want to folks. Technical details of what each field does and how to fill them in can be relegated elsewhere, like in a wiki or 'how-to' doc.

* Have a screenshot of the actual RF antenna being created instead of what looks like an AI generated grid field. Use a screenshot from your application.

* Communicate the limitations of the approach. You're talking about optimizing for SLA 3D printing but will this antenna actual work if 3D printed? Does it need to be out of metal? Some communication about the limitations is fine and, in my opinion, welcomed.

* Discuss some applications or motivation for creating the application (target audience, use cases, etc.). As it stands, it seems like it's very cool but a bit unmotivated

[0] https://en.wikipedia.org/wiki/Luneburg_lens

[1] https://en.wikipedia.org/wiki/Luneburg_lens#/media/File:Lune...

[2] https://www.youtube.com/watch?v=aURuC4Ur84Q

EDIT: added last bullet point

jboirazian
Thanks for the feedback!

Will try to improve on that , first time on hackernews and first time developing a real open source project

mikewarot
None of the parameters have units. Is this meters, feet, inches, wavelength? I'm sure you've done a lot of work, but it's not impedance matched to the user.

How many wavelengths diameter are required for this to work?

For example, how big would a lens have to be to work at 902-928 Mhz for LoraWAN?

jboirazian
Hi mikewarot,

As a general rule, Luneburg lenses need to have a diameter at least equal to the wavelength of the frequency they are designed to operate with. Because of this, Luneburg lenses are more cost-effective at higher frequencies, making them particularly suitable for applications in the GHz range.

It is possible to develop a Luneburg lens for LoRaWAN, and I am currently working on a DRC check for various wavelengths

dbcurtis
Ah, so my dream of a compact beam for the 1.8MHz band still eludes me... :)
mikewarot
You just need a mile or two of wire and a bunch of stakes with an open prarie for a rhombus antenna. ;-)

A roll of wire isn't very big ;-)

frazar0
Very interesting!

It would be even more appealing if you could show a test case where a high level metric (e.g., wifi download speed) improves with one of your lenses compared to a baseline scenario without lense.

Also, I expect the dielectric properties of the printing material will affect the design.

Which printing material have you tested exactly?

Do you know how much the performance changes when cheaper alternatives is used?

jboirazian
Hi frazar0,

We're excited to receive some Radix resin from Rogers Corporation, which is the current standard for developing RF lenses due to its low dielectric permittivity and low loss tangent coefficient.

We also have a few simulated lenses in CST Studio that we will share with you as soon as possible.

mNovak
As an antenna engineer myself, I'm always very glad to see tools and open source that make RF/microwave more accessible as a hobby!

That said, it'd be really great if this could simply be hosted/accessed online. The intersection of RF engineer/hobbyist and knowing how to work with Docker is slim (anywhere other than HN), which detracts from the "user friendly interface".

jboirazian
Hi mNovak!

You are 100% right on that. Im working on deploying a free version to access it online so people can check it out.

Also im working on making a step by step guide so people can install it with docker and looking to other alternative ways to installing it locally

abdullahkhalids
I am confused. This seems to require a single python package. Why is there any need for docker in the first place?
jboirazian
Luneforge is built on top of Pymesh docker image (a fast C++ Python wrapped Geometry Processing Library)

https://github.com/PyMesh/PyMesh

It requires docker cause its the best way to have all the required dependancies for Pymesh

ChuckMcM
Nice work! I look forward to following your development. As a radio amateur I was looking at a Luneburg lens for a 10GHz point to point link, with luck this will let me play around with that idea. Is there a discord server or forum where folks are discussing applications?
jboirazian
Hi ChuckMcM!

If you are interested , i also developed last year a PLA Luneburg lens for Band X (8Ghz to 12Ghz) using a conventional FDM printer.

We obtained a 6dbm gain @10Ghz

https://github.com/jboirazian/LuneburgLensGenerator

https://polar.sh/jboirazian/posts/why-luneburg-lenses-are-co...

ChuckMcM
Awesome. That is pretty much exactly what I was thinking of doing. My thought was that you could more easily weatherize something like this rather than a parabolic dish which has a lot of wind loading.

What filament did you use?

jboirazian
Conventional PLA. Since its the cheapest and surprisingly extremley stable for Ghz range RF applications

I recommed you to read the research paper "Measuring the Electrical Properties of 3D Printed Plastics in the W-Band "

(https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=10...)

It was really useful for us when developing our lens with an FDM printer. Be warn that it does require an infill of 100% , so it will be quite heavy.

GeorgeTirebiter
6 dB gain? 'dBm' is db gain relative to 1 milliwatt of power.
ChuckMcM
Based on the literature the measure would be 6dBi (relative to isotropic). This is often referred to as 'gain' as it represents sensitivity to the band of interest at a given angle of arrival.
GeorgeTirebiter
Yes, antennas are normally measured relative to the theoretical 'isotropic' radiation pattern. Sometimes, dBd is used - gain relative to a dipole.

But, even then, you have pattern E and H plane measurements. https://www.data-alliance.net/blog/antenna-radiation-pattern...

We'll discuss this with an eyeball QSO in November...

ChuckMcM
In the paper they were measuring signal gain between two antennas, and as such the 6dBm gain appears to be the effect of collating more of the beam spread into the receiver (as one would expect of a lens). Given my schedule I don't think I'll have enough time to print one by November but it would make for some excellent discussion! Reading the permittivity paper that was linked here was also quite good and I'm wondering if something could be integrated into openEMS which would tie the two together.

I'm also tickled by the idea of a 'Newtonian' RF telescope using two lenses.

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ta988
Could this be used to make the wifi in my home do right angles and avoid walls? how big would it have to be?
jboirazian
hi!

yes. As a matter of fact while developing this tool as my capstone project at the National Tecnological University here in Buenos Aires , im also planning on developing a 2.4Ghz lens to showcase the capabilities of the project.

2.4Ghz lenses are around 14cm diameter

ta988
Fantastic, what material are they made of?
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anfractuosity
By SLA, does it mean resin printing then using some kind of metal coating process?

Or could you use something like SLS/SLM to print the whole model in metal?

jboirazian
Luneburg lenses for RF are 100% dielectric.

You print your lens with a known dielectric constant uv curable resin and it its good to go!

Methods like this are the ones that Lunewave (https://lunewave.com/) use for developing RF lenses for their ADAS system

aeonik
You say it's optimized for SLA, could it work with FDM? I haven't looked up the dialectic constants for PLA or PETG, but I'm very curious.