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monopole antenna equations

 
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btb4198
Antenna Theory Regular


Joined: 19 May 2011
Posts: 20

PostPosted: Thu May 19, 2011 5:30 am    Post subject: monopole antenna equations Reply with quote

I am trying to design a monopole antenna and a circuit to go with it but I can't find any equations for that. I have read alot and I know about Ampere's law and Faradays' law, but I do not see how that will help me design an antenna.

ok this is what I got...

F = 2.4Ghz.
the distance the signal has to travel is 178 meters.
λ = 0.125metes

Now how do I use that information to to design and build a monopole antenna.

I think when designing an antenna you need to look for: T (thinnest of the wire) L (is the total length of the antenna) is that right?
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Schubert
Antenna Wizard


Joined: 08 Apr 2009
Posts: 161

PostPosted: Thu May 19, 2011 6:31 pm    Post subject: Reply with quote

A monopole antenna should be a quarter-wavelength.

So if f = 2.4GHz, then one wavelength = c/f = 3e8/2.4e9 = 0.125 meters. hence, the Length should be L=lambda/4 = 3.1 cm.

Remember, the monopole should be on a ground plane. The ground plane should be roughly at least lambda/2 in diameter.

As to the thickness of the monopole: thicker is bigger. The thicker the monopole, the more volume it occupies, which means larger bandwidth (less sensitive to exact sizes to resonanate at 2.4 GHz).

The distance the signal needs to travel doesn't affect the antenna design - only the transmit power or receiver sensitivity.

Hope this helps
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btb4198
Antenna Theory Regular


Joined: 19 May 2011
Posts: 20

PostPosted: Thu May 19, 2011 10:22 pm    Post subject: Reply with quote

it does alot!!!

so how do I determine the needed transmit power for a distance of 178 meters?
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wolberine
Antenna Theory Regular


Joined: 01 Mar 2011
Posts: 35

PostPosted: Fri May 20, 2011 4:24 am    Post subject: Reply with quote

You'll want to use the Friis transmission formula for a basic guideline. Then, you'll want to research link budgets to factor in receiver sensitivity, noise issues, bit-error rates, etc. (any loss or gain factors that effect received signal strength). There is a lot of information on the main site as well as Wikipedia.
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