Homemade Sierpinski Gasket Fractal Wifi Antenna

By , February 16, 2011 4:14 pm

I have been hearing about fractal antennas for a little while and wanted to try making my own fractal antenna to try out the concept. Some of the benefits promoted in research papers are the ability of fractal antennas to receive multiband RF signals, and the ability to shrink the size of the antenna while maintaining signal strength. I decided to create a prototype fractal antenna based upon the Sierpinski Gasket fractal pattern.

This antenna is a prototype antenna. I am posting this article on my blog for the benefit of other antenna building enthusiasts. There is still a lot of work required to finish tuning and improving the design. If you are looking for a general purpose WiFi antenna, either a 2.4 GHz patch or grid antenna are simple and effective solutions for most wireless links. I can recommend L-com as a quality supplier of traditional wireless antennas.

I designed my fractal antenna to have a connector that is compatible with my Linksys WRT54GS 802.11g router. This was my first test of the fractal antenna concept and I learned a lot. The antenna has a low gain design and through preliminary testing on a 1/2 km WiFi link with a few trees in the path I achieved a reliable link.

There is certainly lots of room for improvement through more testing, computer simulation, and better design but fractal antennas do work.

You can download a PDF version of the antenna pattern I used.

Fractal Reference Materials

Here are three PDFs that were helpful when I created my fractal antenna:

ECE416 Project Report

Design and Implementation of Compact Microstrip Fractal Antennas (copied from the WaybackMachine Archive)

by Paul Simedrea

www.imaging.robarts.ca/~simedrea/paul-416-report.pdf (Original Link Broken)

 

Sierpinski Gasket Patch And Monopole Fractal Antenna (copied from the WaybackMachine Archive)

By Abd Shukur Bin Ja’afar

http://eprints.utm.my/4429/1/AbdShukurJaafarKPFKE2005TTT.pdf (Original Link Broken)

 

Fractal Antennas

by Philip Felber

www.ece.iit.edu/~pfelber/fractalantennas.pdf

 

Building the Prototype

This is a photo of my completed fractal antenna prototype.

This is a photo of my completed fractal antenna prototype.

I attached a Linksys WRT54GS style RP-TNC Connector to the fractal antenna for testing.

I attached a Linksys WRT54GS style RP-TNC Connector to the fractal antenna for testing.

When I designed my first prototype fractal antenna I was concerned that my home printed circuit board etching process would isolate the Sierpinski triangles so I added coupling patches. Note: Since the toner transfer process was so accurate the next version of the prototype antenna will feature finer triangle contact points between each of the Sierpinski fractal triangle iterations.

When I designed my first prototype fractal antenna I was concerned that my home printed circuit board etching process would isolate the Sierpinski triangles so I added coupling patches. Note: Since the final toner transfer process ended up being more accurate than I expected the next version of the prototype fractal antenna will feature finer triangle contact points between each of the Sierpinski fractal triangle iterations.

The antenna design was laser printed onto Pulsar Pro FX toner transfer paper. This process allows me to copy the antenna design onto the copper clad PCB material.

The antenna design was laser printed onto Pulsar Pro FX toner transfer paper. This process allows me to copy the antenna design onto the copper clad PCB material.

The laser printed antenna design was then transferred onto the sheet of copper clad printed circuit board by a thermal bonding process using modified laminator.

The laser printed antenna design was then transferred onto the sheet of copper clad printed circuit board by a thermal bonding process using modified laminator.

This is the copper PCB material after the first stage of the toner transfer process. The laser printed design has been temporarily bonded to the copper PCB.

This is the copper PCB material after the first stage of the toner transfer process. The laser printed design has been temporarily bonded to the copper PCB.

The next step was to use a laminator to apply the Pulsar Pro FX "Green TRF Foil" to the circuit board. The green foil is used to fill in any toner gaps or thicken uneven coatings in the toner transfer.

The next step was to use a laminator to apply the Pulsar Pro FX "Green TRF Foil" to the circuit board. The green foil is used to fill in any toner gaps or thicken uneven coatings in the toner transfer.

This is the cleaned circuit board with the antenna design freshly transferred. The board is now ready for etching.

This is the cleaned circuit board with the antenna design freshly transferred. The board is now ready for etching.

For this antenna prototype I masked the backside of the PCB with electrical tape.

For this antenna prototype I masked the backside of the PCB with electrical tape.

I used the direct etch method with ferric chloride (FeCL) to etch the circuit board in 10 minutes. The direct etch method is done using a sponge to slowly wipe the ferric chloride chemical over the entire circuit board. As you wipe the PCB board surface the sponge takes away the etched material and coats the board with fresh Ferric Chloride. This is a quick way to make a custom circuit board in your home workshop. Due to the health hazards of using ferric chloride I wore safety glasses and gloves.

I used the direct etch method with ferric chloride (FeCL) to etch the circuit board in 10 minutes. The direct etch method is done using a sponge to slowly wipe the ferric chloride chemical over the entire circuit board. As you wipe the PCB board surface the sponge takes away the etched material and coats the board with fresh Ferric Chloride. This is a quick way to make a custom circuit board in your home workshop. Due to the health hazards of using ferric chloride I wore safety glasses and gloves.

This is the board after the etching process is complete. The toner transfer coating still remains on the etched PCB.

This is the board after the etching process is complete. The toner transfer coating still remains on the etched PCB.

I wiped the etched circuit board down with a swab coated in acetone to remove the toner transfer coating. I used nitrile gloves when cleaning the board down because acetone will soak through the typical latex disposable gloves.

I wiped the etched circuit board down with a swab coated in acetone to remove the toner transfer coating. I used nitrile gloves when cleaning the board down because acetone will soak through the typical latex disposable gloves.

I drilled the hole for the antenna connector using a drill press and a small PCB drill bit.

I drilled the hole for the antenna connector using a drill press and a small PCB drill bit.

For my first prototype I used an RP-TNC connector harvested from a standard Linksys router rubber ducky antenna.

For my first prototype I used an RP-TNC connector harvested from a standard Linksys router 'rubber ducky' antenna.

This is a closeup of the Linksys compatible RP-TNC antenna connector.

This is a closeup of the Linksys compatible RP-TNC antenna connector.

I applied a droplet of water washable flux to the PCB prior to soldering.

I applied a droplet of water washable flux to the PCB prior to soldering.

The next step was to solder the wire from the RP-TNC connector to the base of the Sierpinski antenna PCB.

The next step was to solder the wire from the RP-TNC connector to the base of the Sierpinski antenna PCB.

It only takes a few moments to solder the RP-TNC connector's wire to the fractal antenna.

It only takes a few moments to solder the RP-TNC connector's wire to the fractal antenna.

I soldered the antenna connector's 2nd wire to the PCB ground plane.

I soldered the antenna connector's 2nd wire to the PCB ground plane.

Lastly, I finished the antenna by securing the RP-TNC connector to the antenna with a large glob of hotglue.

RF Simulating the Sierpinski Fractal Antenna

A blog reader Alexander Pelevin was very generous and ran a FEKO RF simulation on the Sierpinski fractal antenna design. He has provided the following images.

Alexander commented that it is important to make sure the Sierpinski gasket triangle elements are in contact with each other and the connection points should be kept as small as possible. Based upon his tip I will have to reduce the size of the coupling patches on my next prototype of the Sierpinski Fractal Antenna down to the fine tips of the triangles.

As a personal observation I find his visualization of the fractal antenna very intriguing because they show the antennas multiband properties. When you look at the following RF simulation images the lower frequency 1.731 GHZ signal has the strongest currents split between the outermost 2nd iteration triangles of the Sierpinski pattern, while the higher frequency 14.268 GHz  signal has the highest currents on the innermost 4th iteration of the Sierpinski pattern.

This is the fractal antennas' simulated RF currents when operating at 1.731 GHz.

This is the fractal antennas' simulated RF currents when operating at 1.731 GHz.

This is the fractal antennas' simulated RF currents when operating at 3.774 GHz.

This is the fractal antennas' simulated RF currents when operating at 3.774 GHz.

This is the fractal antennas' simulated RF currents when operating at 7.393 GHz.

This is the fractal antennas' simulated RF currents when operating at 7.393 GHz.

This is the fractal antennas' simulated RF currents when operating at 14.268 GHz.

This is the fractal antennas' simulated RF currents when operating at 14.268 GHz.

I would like to thank Alexander Pelevin for contributing the RF antenna simulation images to this article.

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37 Responses to “Homemade Sierpinski Gasket Fractal Wifi Antenna”

  1. iqbal says:

    What substrate that you use, is there epoxy or something?

    Can you tell me the dimension formula of antenna sierpinski gasket if I use another substrate... I can't find it.

    Why you make something like feed line, but you use probe coaxial for excitation. What is the purpose?

    Thanks a lot.

  2. Andrew says:

    what substrate that you use, is there epoxy or something?

    I used FR4 PCB material which has a layer of copper bonded to a substrate of fibreglass to create the antenna.

    why you make something like feed line, but you use probe coaxial for excitation. what is the purpose?

    I am a hobbyist so I still have a lot to learn about antenna design. This was my first attempt at a fractal antenna. I will be making more design variations in the future to compare the results.

    Here are three PDFs that might help you:

    Sierpinski Gasket Patch And Monopole Fractal Antenna
    By Abd Shukur Bin Ja’afar
    http://eprints.utm.my/4429/1/AbdShukurJaafarKPFKE2005TTT.pdf

    Fractal Antennas
    by Philip Felber
    http://www.ece.iit.edu/~pfelber/fractalantennas.pdf

    ECE416 Project Report:
    Design and Implementation of Compact Microstrip Fractal Antennas (Pulled from WaybackMachine Archive)
    by Paul Simedrea
    http://www.imaging.robarts.ca/~simedrea/paul-416-report.pdf (original Link Broken)

    Regards,
    Andrew

  3. Iqbal says:

    Oh that's very useful.

    Thank you very much, if I have something problem again, maybe I will ask you again.

    Regards,
    Iqbal

  4. Aakash says:

    What are the exact dimensions of the main triangle?
    and what are the dimensions of FR4 substrate?
    Thanks!

  5. Andrew says:

    Hi Aakash.

    The copper triangle was 2.7 inches wide by 2.3 inches high. The FR4 fiberglass backing substrate was 4.1 inches by 4.1 inches. This was my first attempt at making a fractal antenna so I'm sure there is lots of room for improvement in the design.

    Here is a PDF version of my first fractal antenna design:
    Andrew_Hazelden's_Serpinski_Antenna.pdf

    I would love to hear from anyone if they come up with improvements after testing the design.

  6. Aakash says:

    Thnx a lot!!

    Working on it if something better comes will let you know.

    Regards,
    Aakash

  7. tarek kheder says:

    Does this really work !!!!

  8. Andrew says:

    Hi Tarek.

    The Sierpinski Gasket Fractal Antenna does work but it is just the first prototype version. The design hasn't been tuned with a spectrum analyzer yet so there is a lot of room for improvement. I would only recommend this antenna design if you are into building antennas for fun.

    If you are looking for a high performance WiFi antenna a regular 2.4 GHz patch antenna is a good choice.

  9. Asif Mehmood says:

    Hi Andrew how are you? I want to know the complete dimensions of this wifi antenna because i want to implement it. How i can use it in my home?
    thnxxxxxx

  10. Asif Mehmood says:

    Hi again...I also want to know that, should I direct print the prototype and do further procedure or should I use any software like ORCAD or HFSS to implement the layout?????
    Please reply soon....
    Thanks

  11. Hassan says:

    Hi. I am trying to use fractal antennas for vehicles for DAB reception is that possible?

  12. Andrew says:

    Hi Hasan.

    I don't personally have any experience with DAB equipment. A traditional antenna would probably be the easiest thing to use with DAB gear if you are looking for a reliable turn-key solution.

    It should be possible to use a fractal antenna with a DAB radio but would require research and experimentation to come up with a quality design. You would need to tune the design to work best with the specific frequencies you are trying to receive.

  13. Nizam Ismail says:

    Hi Andrew....

    I Looked at this set-up.... http://www.poyntingdirect.co.za/pWBS2400/WiFi-Base-Station---24-GHz.aspx and really would like to have something or similar to this..... have you any design ideas similar or point me to where I can find info.... these prices is really way out of budget... let me know

  14. Nizam Ismail says:

    How does the beamforming technology work....?

  15. Andrew says:

    Nizam,

    The link you provided to the Wavion WBS-2400 WiFi Base Station is pretty neat. I find it interesting how they took the idea of antenna diversity to the next level with beamforming technology. I have seen beamforming used for things like marine based hydrophone arrays but it is really innovative for RF applications. The only area where this technology might have some trouble is when using high-gain 24 DBi grid antennas for long shot wireless links.

  16. thannainghtwe says:

    Thank you.

  17. wlad46 says:

    What is the thickness of the material used by you FR4?

    Thanks in advance.

  18. wlad46 says:

    I have such a situation. To the access point trees and foliage, there is no direct line of sight (tried different antenna did not help. I would like to repeat your results.
    I am interested in the thickness of the material that was used and the exact size). Pre bologdaren Vladimir

  19. Andrew says:

    Vladmir,
    Your best bet for a good wifi link through lots of trees and foliage is to get a 700 MHz or 900 MHz access point. The lower frequency WiFi signals aren't absorbed like standard 2.4GHz signals are. I have purchased an embedded WiFi radio from Ubiquiti Networks and found they make quality gear.

  20. wlad46 says:

    Hi! Yes agree, excellent equipment but we can not because you want to get a license for veschanieya 900 MHz. Allowed to use the current 2.4 GHz and then at a power of 250 milivat. Not for nothing did as asked antenna.
    Since the spring did link to the 500 meters at rostoyanii branches (without leaves)
    D-Link 300 flashed dd-wrt and was made a homemade antenna Bi Quad, not tested on the level of the signal (.
    The next day the whole link was lost (I think that a weak signal (antenna)
    So you ask how you did and what antenna parameters.
    interested in the size, thickness of the material.
    Thanks in advance, Vladimir

  21. Andrew says:

    Vladmir,

    If you are planning on building your own fractal antenna make sure to read the three PDF files I listed at the top of my blog post for reference. They are all very informative. When I created my first prototype fractal antenna I used the fibreglass PCB material I had on hand. It think it was a FR4 1/16" copper clad PCB board.

  22. Marcus says:

    Hello Andrew,

    Have you by any chance tried to simulate your antenna in a program like NEC or Zeland IE3D?

    Just curious,
    Marcus

  23. Andrew says:

    Marcus,

    I have never used electromagnetic simulation software before. What RF simulation software would you recommend for an electronics hobbyist interested in antenna design?

    Regards,
    Andrew

  24. Andrew says:

    Hi Anglophony.

    Thanks for sending me the link to 4nec2 website. I really appreciate you taking the time to let me know about this program! This software looks like it will be able to help improve the fractal antenna's performance.

    When I get a spare moment I will have to start learning how to use the 4nec2 antenna modeling program.

    Regards,
    Andrew

  25. ABDUL AZIZ says:

    Hi,

    I want a design of antenna dual band 2.45Ghz & 5Ghz?? I really want it for me to fabricate in accuracy. I study in diploma electronic control but I'm really interested to know more about telecommunication. Here is my email djbink92@hotmail.co.uk

  26. Design Circuit Board says:

    I have read above all post it's really informative and useful in my work so thanks to share it and keep it..... After viewing this post I will try my self to make this circuit board.

  27. Ola Dunk says:

    Hi.

    Can low frequencies fit small sized fractal antennas? I've got a space of 25 mm radius circle and 10 mm height. The antenna must resonate at vhf band iii (174 - 240 Mhz)

  28. Andrew Hazelden says:

    Hi Ola.

    Thanks for your question. I haven't had the time to take this project further than my first prototype but I'm looking forward to spending more time this year learning RF simulation.

    Since this post has been very popular, one of the blog readers might be able to answer your question.

    Regards,
    Andrew

  29. arman says:

    Hi.

    I need help to simulate a Sierpinski dipole fractal antenna with hfss in 2.4ghz freq. Can you help me???plz...

    I'm working foe optimization this antenna and need to simulate this antenna...
    Thanks...

  30. Dman says:

    I am thinking of using fractal antenna to transfer wireless energy... Can some one help me how I can match frequency or any other advice?

  31. Alexander says:

    Andrew, good job. I used FEKO to simulate serpiensky gasket fractal monopole. Can you explain why tops of triangles are rounded?

  32. Andrew Hazelden says:

    Hi Alexander.

    On page 45 of Abd Shukur Bin Ja’afar's thesis "Sierpinski Gasket Patch And Monopole Fractal Antenna" he mentioned the use of a coupling patch to allow a Sierpinski fractal antenna structure to radiate more effectively by lowering the resistance between the iterations of the isolated triangles.

    When I created my first prototype fractal antenna I made it using a homemade printed circuit board that I etched by hand. I was concerned with the accuracy of my toner transfer and etching process and the possibility of isolated / detached triangles. As a solution to that problem I included a modified version of Abd Shukur Bin Ja’afar's coupling patch technique.

    I would love to see a screenshot of your FEKO simulation.

  33. jean says:

    Hi, I'm someone who doesn't know much about antennas but I am making one anyway. I'd like to know which wire from the connector you soldered to the fractal antenna as the wire originally had two. I think the other one is to complete a circuit but you don't have to do that with the antenna? Thank you

  34. Paulo says:

    Please I want the Sierpinski Gasket antenna for UHF.

    RGDS
    Paulo

  35. Sahar says:

    Cool!

  36. Adrian says:

    Hi Andrew, good job for the antenna! I would like design a simmilar antenna, but for GSM communications (900/1800 MHz). Could you suggest some physical dimensions for this type of antenna? I`m a little bit confused about choosing the right size.
    Thanks a lot!