Fractal Antenna for 433MHz LRS

[Mictronics]

This dipole antenna is a result from my experiments with fractal structures I did in the past few weeks.

The antenna design is a half wave dipole based on a Koch fractal curve. Advantage of the fractal is the reduced physical dipole size while the electrical length is equal to lambda/2.

Comparing the physical length of 278mm for a straight dipole to 168mm of the Koch fractal, there is a reduction of ~40%.

The antenna was designed for 433MHz and will be used together with my EzUHF.
My indention is to place a dipole on the outside of each the Winglet.

I made two version of the antenna which are different in shape of the fractal curve and which also results in different physical length of the antennas.
Board size is 200mmx40mm and 170mmx40mm.

Return loss could be better but is a trade-off for smaller dimensions of the dipole trace. A width trace will result in better return loss but length must be increased then.

Simulation vs. measurement results:

200mm version
170mm version

[sircana]

Mate, you are pushing the limits. This is a serious job...

[Mictronics]

It's just a dipole...

Btw, I simulated with HFSS and CST both came to different results. The boards were made after HFSS and this simulation is close to reality. CST is far off with simulated dimensions. Not sure why is that, might be a setup problem.

[Trappy]

haha, I dont care how well this works, this will go down into history as the coolest antenna ever looking forward to see this go into production (will it ever?). Very well done, my friend, I kneel before thee!

[IBCrazy]

Incredible work, Michael! Wild looking design, too. Why did you choose the Koch fractal curve?

-Alex

[Mictronics]

Trappy, production isn't a big deal. I made the prototypes at home within 1 hour.

Alex, the Koch fractal was choosen since it can be calculated easy from a straight dipole. In simulations I perform on-the-fly calculation of the trace so the optimizer can do it's work.

Next I will look into a Hilbert curve to make the boards more square so they will fit better to winglets.

[ssassen]

Positively love it!

[Windbreaker]

Can you do one for 900 mHz that will work on the boom of a helicopter? Maybe replace the tail fin?

[sircana]

It's just a dipole...

Btw, I simulated with HFSS and CST both came to different results. The boards were made after HFSS and this simulation is close to reality. CST is far off with simulated dimensions. Not sure why is that, might be a setup problem.

I have been told by some RF doctors that you shouldn't trust too much simulation softwares. Each one does his job better for a specific type of antennas, and it is very common to find discrepancies. Clearly for this design HFSS seems to work better. Just one idea: instead of attaching the antenna to the winglet, why don't you try to give it the exact shape of the winglet, and just use the PCB as the winglet? I am starting to think about fully integrating the antennas (video and RC) into the plane's structure.

[Jan]

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