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novorado
Antenna-Theory.com Newbie
Joined: 24 Apr 2012
Posts: 3
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 Posted: Tue Apr 24, 2012 1:12 pm Post subject: Hilbert / Peano / Fractal antennas |
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Thanks for outstanding effort Pete. In course of my work I need to design quad-band gsm and gps antenna for an embedded m2m application, and I've found a number of recent academic work on Hilbert / fractal antennas.
Looking on your site and inside my iphone / android, looks like telecom engineers rather prefer sticking to inverted-f or other kind of multi-band antenna technology. Why do you guys avoid using hilbert type in mobile apps - is it engineering complexity to implement and simulate or it's impractical for some other reasons i do not understand?
Would be great if you can extend your fantastic materials with fractals.
Thanks! |
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bigSteve
Antenna Wizard
Joined: 14 Mar 2009
Posts: 265
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| Posted: Tue Apr 24, 2012 2:50 pm Post subject: |
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THe complexity of the Hilbert antenna is significantly less than the other challenges faced in producing a mobile phone today. So no, it is not complexity.
Mobile phones must operate at the lowest frequency of about 900 MHz, for which the half wavelength is 6.5". Given the size of the phone is less than this, you are lucky to get a dipole type antenna in there - basically the ground/circuit-plane of the device is one arm of the dipole, and the other side is whatever you choose to make, inverted-F, whatever.
Further, if you try to use a fractal antenna it would necessarily have all the electronics (circuit boards, camera, touch screen) and metal sitting on top of it, and grounded throughout. As such, the current would not follow your fractal contours even if you designed it, as everything else around it that was conductive would make it look more like a flat sheet of metal. So no, it won't work and wouldn't be in the running for a modern phone in the current sizes. |
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novorado
Antenna-Theory.com Newbie
Joined: 24 Apr 2012
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| Posted: Tue Apr 24, 2012 5:18 pm Post subject: |
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| bigSteve wrote: | THe complexity of the Hilbert antenna is significantly less than the other challenges faced in producing a mobile phone today. So no, it is not complexity.
Mobile phones must operate at the lowest frequency of about 900 MHz, for which the half wavelength is 6.5". Given the size of the phone is less than this, you are lucky to get a dipole type antenna in there - basically the ground/circuit-plane of the device is one arm of the dipole, and the other side is whatever you choose to make, inverted-F, whatever.
Further, if you try to use a fractal antenna it would necessarily have all the electronics (circuit boards, camera, touch screen) and metal sitting on top of it, and grounded throughout. As such, the current would not follow your fractal contours even if you designed it, as everything else around it that was conductive would make it look more like a flat sheet of metal. So no, it won't work and wouldn't be in the running for a modern phone in the current sizes. |
I just read a number papers on fractals, claiming directly opposite views; Looks like fractals is a holy war zone for antenna community.
While everyone seems to agree that it's much smaller size for the same emitting wire length main problem that ppl report is that it has great ohmic resistance and accumulates energy in a near field, thus this design look ineffective, for some.
A storng advocate
".. proposed antenna achieved good omnidirectional radiation pattern and circular polarization performance. .. could be suitable for the application in WLAN/WiMAX communication systems" - jan 2012 paper
Group of practical folks from Europe in 90-degree disagreement on that
"experiences from this work also show that other intuitively generated Euclidean configurations perform better than
prefractal structures with the same size-reduction ratios" -- Are Space-Filling Curves Efficient Small Antennas?
Russian military seems to be using hilbert a lot in a small flying devices from 1980's.
I feel like degree of enthropy increases in my head. Thanks a lot for your hints! |
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bigSteve
Antenna Wizard
Joined: 14 Mar 2009
Posts: 265
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| Posted: Wed Apr 25, 2012 3:45 am Post subject: |
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| There is no debate. Those papers are nonsense and written by people who have never put an antenna into a real product. No integration details are in there. |
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novorado
Antenna-Theory.com Newbie
Joined: 24 Apr 2012
Posts: 3
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| Posted: Wed Apr 25, 2012 9:30 am Post subject: |
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| bigSteve wrote: | | There is no debate. Those papers are nonsense and written by people who have never put an antenna into a real product. No integration details are in there. |
Industrial research seems to be 10+ years ahead of sicentific. I guess to sanely fit such an antenna into miniature device or SoC (which can be much smaller than a cell phone), one has to run full-device simulation, probably including digital logic signals+spice, device casing, pcb; which does not look as an impossible task considering novadays level of eda tools design.
Anyway, there is number of known military and commercial applications with fractals and space-filling antennas; But tooling and methods certainly out of reach for a small consulting company.
Thanks Big Steve. I actually obtained a commercial sample of similar previos-generation product and I can see ppl use cermaic antenna with circular polarisation (which is very hard to implement on FR4 material) and pcb trace monopole around the microwave digital transmittion module (I guess that shape they cut out experimentally) |
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