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xcyyx
Joined: 29 Jul 2006
Posts: 22
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 29 Jul 2006 8:56 wp_omni_wireless.pdf |
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| Hi everyoen , do you have some idea how to design a broadband omni antenna , 3.3-3.8GHz, can you kindly give me some suggestion?thanks in advance
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unkarc
Joined: 28 Apr 2001
Posts: 287
Helped: 36
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29 Jul 2006 11:05 omni-directional broadband short dipole antenna |
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Hi,
Maybe you can use ideas shown here to adopt for your frequency:
http://www.centurion.com/home/pdf/wp_omni_wireless.pdf
http://www.mwjournal.com/Journal/article.asp?HH_ID=AR_458
http://www.dxzone.com/catalog/Antennas/WiFi/
Regards
unkarc
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xcyyx
Joined: 29 Jul 2006
Posts: 22
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29 Jul 2006 15:09 omnidirection antena |
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Unkarc,
Thanks for your help. I need 11dBi GAIN, and I am confused with how to design the feedline , I did some simulation , but looks difficult to meet VSWR below 1.5 .
do you have another good idea?Thanks for your great help again .
Best Regards
Cheng
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jian
Joined: 08 Sep 2003
Posts: 873
Helped: 151
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29 Jul 2006 17:11 hf broadband omnidirectional antenna design |
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Hi, Cheng:
Your requirements seem interesting. You want an omni-directional antenna with 11 dBi gain. I am not sure whether you can achieve it. When an antenna is kind of omni-direction, you should not have gain on it unless you use active devices and consider the gain from the active devices as the gain of the antenna. Regards.
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xcyyx
Joined: 29 Jul 2006
Posts: 22
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30 Jul 2006 3:53 omni directional attena |
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Hi Jian ,
The gain 11dBi means it's omni array antenna , passive array , do not add active device, so ,the issue is it should be broadband and good omni performance. I still have no good idea for this design.
Regards
Cheng
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30 Jul 2006 3:53 Ads |
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unkarc
Joined: 28 Apr 2001
Posts: 287
Helped: 36
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31 Jul 2006 14:06 broadband hf vertical antenna pdf |
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To Jian:
I understand your dilemma on omnidirection and gain but please consider the followings: usually an antenna's radiation pattern is characterized in both the Horizontal and the Vertical planes.
You surely know the quarter wave vertical or monopole antenna which is omnidirectional but in the Horizontal plane ONLY! It surely cannot radiate upwards as a dipole antenna cannot radiate towards the directions of its endings, right?
Now if you place an identical quarter wave antenna above the first quarter wave one (this is called stacking of antennas) and feed both antennas at the same time (i.e. connect them appropiately), then the omnidirectional radiation remains but there will be even less radiation upwards the sky (towards the top endings) so put it in another way: we have achieved some gain in the horizontal (omi)direction by supressing some radiation in the vertical plane. The more quarterwave antennas we stack one above the other , the more gain we will have in the horizontal plane and we will still have omnidirectional radiation!
See this two links for some more on this but if you google search with key words like "antenna stacking" you will find further good examples:
http://www.kyes.com/antenna/stackluge.html and also see Fig.22 in this link:
http://www.ncjrs.gov/pdffiles1/nij/185030b.pdf
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To Cheng:
Sorry, I do not have experience with wideband antennas in the GHz range, I cannot really give you further useful advice (I am familiar with short wave and VHF/UHF antenna topics mainly and the bandwidth is usually a few percent only so the matching is not so hard).
What I finally can tell you is that in case you modelled vertically stacked quarter wave antennas from one of the links I gave earlier to you, then the matching is mainly affected ,I think, by the sleeve at the bottom feed point.
Try to google search for key words like "wideband antenna matching" and the like.
Regards
unkarc
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