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adel elshahed
Antenna-Theory.com Newbie
Joined: 03 Oct 2011
Posts: 9
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 Posted: Mon Mar 26, 2012 1:29 pm Post subject: matching of helical antenna |
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| what is the parameter that affect on the matching of the helical antenna ??? i have read on balanis handbook that i should make( at the end of the spiral) a small sheet of metal (narrow at the side of helix and wide at the port) ,i have already done that on the simulation (cst microwave studio), but the s_11 is the same in case of no sheet of metal ( the reading s11 = -5 db) |
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bigSteve
Antenna Wizard
Joined: 14 Mar 2009
Posts: 265
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| Posted: Mon Mar 26, 2012 6:38 pm Post subject: Impedance Matching for Helical Antenna |
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What frequency range are you trying to match over? Also, what is your desired s11?
If it is narrow band you can always use a simple impedance matching network like an L-C circuit at the feed that will do the trick.
I'm not sure about the method of using the small sheet by the helix. You can also try adjusting the geometry to get the impedance right (number of turns, length, turn rate, wire diameter, etc). |
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adel elshahed
Antenna-Theory.com Newbie
Joined: 03 Oct 2011
Posts: 9
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| Posted: Mon Mar 26, 2012 8:39 pm Post subject: Re: Impedance Matching for Helical Antenna |
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| bigSteve wrote: | What frequency range are you trying to match over? Also, what is your desired s11?
If it is narrow band you can always use a simple impedance matching network like an L-C circuit at the feed that will do the trick.
I'm not sure about the method of using the small sheet by the helix. You can also try adjusting the geometry to get the impedance right (number of turns, length, turn rate, wire diameter, etc). |
my frequency rang 200 MHZ from 2300 MHZ to 2500 MHZ ,the transimetted power from my aplication is very small ( in order of few m watts) so i want s11 to be very small to reduce the reflected power , I use the design equations in balanis handbook so i afraid i make it worse if i change any thing
i have read that the impedance of helical antenna is purely real but the simulation give me imaj. impedance on the smith chart , what do you think i should do?? thanks |
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bigSteve
Antenna Wizard
Joined: 14 Mar 2009
Posts: 265
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| Posted: Mon Mar 26, 2012 9:42 pm Post subject: Impedance Matching and Smith Charts |
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With such a small bandwidth you will not have trouble doing impedance matching. Just add a simple lumped element network at the feed. It should only be two components. This tutorial has information on impedance matching via the Smith Chart:
http://www.antenna-theory.com/tutorial/smith/chart.php |
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