omnidirectional antenna
Is it possible to design an omni directional circularly polarized microstrip antenna using single fed ?
I'm using HFSS and I had some ideas, but the results are still bad.
Can you give me some advices?
Thanks
i dont know abt hfss
but in pcaad u can design
check this link out for circular polarization. Obviously, this cant be used on a patch because it won't be omnidirectional but its a good read for any antenna design engineer anyway.
http://www.mwjournal.com/Journal/art...p?HH_ID=AR_453
I am also doubt about whether there exists omni-directional circular-polarization antenna, not matter in what forms.
Since I reviews all the antennas I know for circular polarization, such as microstrip antenna, helix antenna and so on, all of them are only broadside or endfire, but not omni-directional.
I am not sure whether the antenna arrays can generate the pattern with omni-directional circular polarization, but I think even it would, at some angle the axial ratio should be not acceptable.
Hi:
I am afraid there may not be any omni-directional antenna for circular polarization. Normally, if an antenna is RHCP in one direction, it will be LHCP in the opposite direction. From RHCP to LHCP, there will be a point with no radiation or with linear polarization only. Otherwise, it can transit from RHCP to LHCP. Regards.
There is possible to build an omni-directional antenna for circular polarization, but unfortunately not in microstrip.
http://www.ee.kth.se/php/modules/pub...S3-EX-0523.pdf
http://members.aol.com/k5oejerry/eggbeater2.htm
Sure. There are planar types of antennas for omindirectional dual polarization. Here is one at low frequency for use on an airplane. You could make the same type of antenna in microstrip. I am no antenna expert, but I think the crossed slot antennas need a resonant structure on the ground plane side.
Circularly polarized omnidirectional antennas are possible. One type is a Lindenblad. It however is not strictly planar.
I can imagine an antenna using a planar patch element producing circularly polarized energy in a somewhat focused beam. Place the patch in the horozontal plane and let it radiate upwards along the z axis. Now place a cone with the vertex at the origin so that it spreads the beam into the horizontal plane and you have a circilarly polarized omni-directional antenna. Strictly this is omni in the xy plane which is often what is intended.
I have used this technique with a turnstile instead of a patch. It does work.
Other possibilities also exist. Consider the wide types of GPS antennas these are generally hemispheric in their coverage and RHCP. A quadrifilar helix is a particularly good type here.