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Isotropic antenna with 100 kHz- 6GHz BP

 
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Fadoua
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Joined: 08 Jul 2016
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PostPosted: Fri Jul 08, 2016 1:13 pm    Post subject: Isotropic antenna with 100 kHz- 6GHz BP Reply with quote

Hello guys !

I need to design an antenna for an EM field probe with a bandpass of 100 kHz to 6GHz. After some heavy research, I found that the best way to make my antenna is by making a dipole which radiates on this frequency band and repeat it 3 times on a pyramid to verify the isotropy. The problem though is that I still can't design a dipole which radiates on this suuuuper ultra wideband. The maximum I could do was from 3 GHz to 6 GHz but the size of my dipole turns quite big (around 20 cm) if i'm correct and I need a really small antenna-(1-2 cm if possible).

so, I wanted to ask you guys for some help, hopefully someone has an idea to suggest.

Thank you in advance. Smile
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admin
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Joined: 03 Jan 2007
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PostPosted: Mon Jul 11, 2016 12:04 am    Post subject: Reply with quote

The wawvelength for 100kHz is 3km. So you have no chance of making a 1-2cm antenna that functions even remotely at that frequency
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Fadoua
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Joined: 08 Jul 2016
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PostPosted: Mon Jul 11, 2016 7:42 am    Post subject: Reply with quote

Maybe not 1-2 cm but still I can try making one around 5cmx5cm at least ? The mobile antennas manage to radiate at around 800MHz though they are quite small. Isn't it possible to do the same with a microstrip antenna that radiates at 800 MHz to 6GHz ? They must be other techniques for reducing the size of the dipoles beside the folded dipole technique and as well as increasing the bandwidth (other than increasing the volume). I was also thinking about the electrically short dipoles but I still can't manage to define the dimensions.

There are already quite small commercialized probes with an antenna which radiate from 100 kHz to 6 GHz. So I guess there must be a way somehow?


Thank you so much for your response.


A desperate RF Engineering Student.
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helix
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Joined: 29 Jan 2015
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PostPosted: Tue Jul 12, 2016 2:01 am    Post subject: Reply with quote

It is possible, the constraint is how much sensitivity do you need.

In fact a quick search showed a product like this already exists.


http://www.arww-rfmicro.com/html/18200.asp?id=1124
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Fadoua
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PostPosted: Tue Jul 12, 2016 9:03 am    Post subject: Reply with quote

I was hoping for a decent sensitivity (the ideal would be detecting from 0.1 V/m) but I don't mind at first a lower sensitivity around 3 V/m for a try.

This is exactly the kind of products I have to design !
Unfortunately, I don't have an exact idea concerning the technology adopted. I've looked through few articles on IEEE unfortunately I don't manage to find the correct dimensions for my dipole, the dimensions given are often narrow band compared to what I want. Shocked

Any ideas for the choice of the antenna ?

Thank you so much in advance for your help !!




A 'still' desperate RF engineering student.
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helix
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PostPosted: Thu Jul 14, 2016 12:51 am    Post subject: Reply with quote

http://www.comsistel.com/HAM%20documents/kanda2.pdf

Is a good start.
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Fadoua
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PostPosted: Mon Jul 18, 2016 10:13 am    Post subject: Reply with quote

Got it !

Thaaaaank you so much !
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