
Evolved antenna - zilic
https://en.wikipedia.org/wiki/Evolved_antenna
======
aequitas
Reminds me of an old article about evolutionary circuit design. The computer
was tasked with creating a osscilator using physical hardware. It created a
really complex and unconventional design that no-one understood, but it
worked, only not work outside of the lab. As it turned out the algorithm had
designed it in a way that it used the radio noise from the computer it was
running on as a source. It had effectively made an antenna.

~~~
scrooched_moose
Was it Creatures From Primordial Silicon?

[http://www.netscrap.com/netscrap_detail.cfm?scrap_id=73](http://www.netscrap.com/netscrap_detail.cfm?scrap_id=73)

They used a FPGA for voice detection. It was fascinating they didn't
understand how it worked, and it wasn't a universal design because it depended
on manufacturing variation.

~~~
jccalhoun
I read about the same research in an article in Discover Magazine:
[http://discovermagazine.com/1998/jun/evolvingaconscio1453](http://discovermagazine.com/1998/jun/evolvingaconscio1453)

~~~
mpl
This article is what made me decide to major in CS. I very much remember
reading it in my high school library during the final few days before
graduation. Every time I see it mentioned somewhere I get that feeling . . .
not quite nostalgia, but a reminder of why I love what I do.

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dbcurtis
Interesting to see this antenna here. I heard the creator speak at a local
IEEE event a few years ago. Quite remarkable. Nobody would intuit an antenna
design like that. Great demonstration of the power of GA.

Antenna optimization software has changed antenna design completely. Before
wide-spread computer simulation, there was an awful lot of antenna range cut-
and-try. Antennas are much better now. Learning to drive the modeling software
is still a huge amount of work, but the results are well worth it.

An example from the world of amateur radio: the only popular HF tri-band beam
to survive from the pre-simulation days is the KT-34 and big brother KT-34XA,
originally from KLM. I was talking to Mike Stahl about it (The M in KLM, also
one of the M's in M-squared) and he said he spent months going up and down
towers at an antenna range. Pretty much all other hand-tuned competitors from
that era have fallen by the wayside, the new simulation-verified designs being
much better.

Mike is a great hands-on antenna designer -- when the Stanford dish was new he
designed several feed horns for it.

~~~
guelo
Are the software radiation simulations accurate? Are they based on solving
complex physics formulas?

~~~
dbcurtis
Well..... for some definition of accurate.

For large antennas with thin structures, the typical solver is "Method of
Moments". NEC2 was developed by the government and is public domain. It is
quite popular, and does some things well but it is also easy to stumble into
modeling bugs/deficiencies, and isn't much use above high UHF. But is very
useful if you know how not to step in the bugs, and is free. NEC4 falls under
ITAR, the last I heard. So it isn't particularly hard to get a license, but
you have to clear ITAR.

Microwave structures are more often done with a finite-element model, as I
understand it.

Both rely on numerical approximations to Maxwell's equations. At least for
MoM, each element cheats the boundary conditions a bit in order to make the
problem tractable. With a fine enough grid, you get a good enough answer.

Another friend that has started two antenna companies is an NEC4 guru. I asked
him: "How can I tell if my model has a small enough grid?" Him: "Keep reducing
the mesh until the answer stops changing. When it stops, you had enough
elements in the previous try." Antenna modelling is a bit of an art, I'm not
expert, just hack a few as a hobby.

~~~
guelo
Sounds like there's some manual steps to create the simulation. I'm wondering
how these genetic algorithms can automatically feed into the simulation and
get back a single number to drive the GA fitness function.

~~~
dbcurtis
Well, I used a Yagi optimizer at one point. With that system, the antenna was
parameterized. I specified certain fixed values, like overall boom length and
nominal element diameter, and total number of elements. The element lengths
and spacings were free for optimization. Fitness function was a scoring of
front-to-back ratio, front-to-side ratio, and max allowable SWR over a
frequency range of interest, with a goal of maximum forward gain. The
optimizer tuned the free variables.

For different applications the various scoring measurements would be adjusted
differently. (Sometimes you care greatly about minimizing back and side lobes,
other times not so much, for instance.)

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joe_the_user
Took a few clicks to find the referenced paper as PDF,

So here it is:

[https://www.researchgate.net/profile/Greg_Hornby/publication...](https://www.researchgate.net/profile/Greg_Hornby/publication/226096470_An_Evolved_Antenna_for_Deployment_on_Nasa's_Space_Technology_5_Mission/links/5447e2fb0cf2d62c30526293/An-
Evolved-Antenna-for-Deployment-on-Nasas-Space-Technology-5-Mission.pdf)

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tabtab
Skipper: "Professor, why did our rescue radio fail?"

Professor: "Hmmm, it looks like somebody straightened out the antenna. It had
an unusual shape for a reason."

Skipper: "Giillligan?! Do you know anything about this antenna?"

Gilligan: "Uh, I'm sorry guys, the antenna looked all bent up, so I
straightened it. See how _nice_ it looks now?"

(They both bop Gilligan on the noggin.)

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nomel
I accidentally "evolved" a microwave antenna in my microwave oven, once.

I put some hematite sand on the top of a glass plate that was suspended about
5 inches from the bottom of the microwave oven. I wanted to see what kind of
pattern the standing waves would heat the hematite to (this microwave didn't
have an RF stirring fan).

Instead of some standing wave pattern, I ended up with a fractal like antenna
that grew from a molten blob in the middle. The initial molten blob extended
into arms of molten material, with each arm necessarily extending in the
direction that maximized RF absorption, causing additional material to melt.
It grew brighter and brighter as it extended, reached some peak, then some of
the arms shorted and it dimmed. Then the plate shattered from the heat.

I wrote some software that converted the picture into antenna elements for
some free antenna simulation package I found at the time, but it couldn't
support enough elements to get close to the shape of the antenna and would
just crash beyond 10 or so.

I'm not sure how useful of an antenna it would be, since it was maximized to
generate heat, but it was a neat kitchen experiment.

~~~
bradenb
I would love to see pictures or a video of this in action!

~~~
nomel
I don't have a video, and I can't find the original picture, but here's a very
low resolution version:
[https://pbs.twimg.com/profile_images/378800000340843432/c1f1...](https://pbs.twimg.com/profile_images/378800000340843432/c1f1f74b9f2e4951fad9fbefef55467c.png)

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adfm
If you’re interested in generative design beyond antenna construction, check
out what Autodesk has been doing:
[https://www.autodesk.com/solutions/generative-
design](https://www.autodesk.com/solutions/generative-design)

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auslander
And then there is phased arrays, a computer-controlled array of antennas which
creates a beam of radio waves that can be electronically steered to point in
different directions without moving the antennas.

Pure math (matrix of delays per element). Go crazy :)

[https://en.wikipedia.org/wiki/Phased_array](https://en.wikipedia.org/wiki/Phased_array)

~~~
taneq
The same thing is used in ultrasounds (except with sound) which is how they
can "scan" without having any moving parts. Super cool.

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elil17
They say this is only used rarely. I’m curious why people wouldn’t design
every antenna this way

~~~
tomatotomato37
Talking less about antennas but more about the overall concept, most
evolutionary algorithms don't take manufactoring into account at all, so they
tend to be a pain to actually build.

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walrus01
Evolved antennas are good for certain purposes, but for highly directional
links, the laws of physics say that there isn't much better than some
variation on a human + CAD + Matlab designed parabolic reflector (whether it's
center feed, compact cassegrain, elliptical offset feed, etc).

Take a look at the dishes used for 71-86 GHz band mmwave links for instance.

~~~
dbcurtis
"Better" when the goal is a very narrow beam pattern and minimal side- and
back-lobes. That isn't always the goal.

For instance, putting your entire FCC city-of-license within your grade A
signal contour from X miles away at a bearing of B. Or, in one case I am aware
of, covering your puny city of license in one direction, and incidentally
getting good coverage into the much bigger city off the back of the beam so
that your sales department can get some traction selling advertising.

~~~
walrus01
Not my field, only related to it, but looking at the ERI antenna catalog, they
resemble human designed variations on yagi, dipole and log periodic
antennas...

[https://www.eriinc.com/catalog/antennas/](https://www.eriinc.com/catalog/antennas/)

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stefs
> This sophisticated procedure

evolutionary algorithms are anything but sophisticated. i love them, but
sophisticated they are not.

~~~
crimsonalucard
The results are sophisticated.

~~~
heavenlyblue
Evolutionary algorithms are just a variation of pseudo-random search.

~~~
k__
Sophisticated is (also) a synonym of convulted.

~~~
crimsonalucard
All of us are products of evolution. Either you are sophisticated or
convoluted. Choose.

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dnautics
not in the article (or the linked): Over the lifetime of the spacecraft, Did
it perform as well or better than the conventional? Does anyone know?

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chris_va
Probably worth revisiting with Q-learning

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rc_kas
I <3 NASA

