antenna-theory.com

[ani]

hi,
i need help to check polarization of my antenna,i have designed it on hfss and for checking polarization i am plotting rEx and rEy and using Ey/Ex i found axial ratio of 2 db now can i say my antenna is circular polarized?while when i draw axial ratio vs frequency i got curve having min value of 2 db but portion of frequencies below 3 db is very small so is my antenna circular polarized?plz guide me about it

[bigSteve]

Axial ratio doesn't necessarily tell you that the antenna is circularly polarized. It means there is energy in both the horizontal and vertical polarizations. This is a necessary but not sufficient condition for circular polarization.

You also need the polarizations to be 90 degrees out of phase with each other.I think HFSS gives you teh ability to plot the radiation pattern as RHCP and LHCP. Otherwise you'll have to think of something clever to check it, like rotate your antenna 45 degrees and see if the axial ratio changes.

No antenna will be perfectly circularly polarized over a wide frequency range, it's an optimization process.

[ani]

thanks steve for your answer ,so should i plot Erhcp and Elhcp on polar graph then from that graph how can i guess about phase of vectors??can u please attach any figure of hfss which can clear me.thanks

[shayanjameel08]

Yeah when choosing an antenna, it is an important consideration as to whether the polarization is linear or elliptical. If the polarization is linear, is it vertical or horizontal? If circular, is it RHC or LHC?

[R. Fry]

If it will help, here are links to information based on the use of NEC about an RH c-pol element used for FM broadcast applications.

Axial ratio and wire model:

http://s17.postimg.org/5z29m6t5r/C_Pol_Element_98_MHz.jpg

Geometry Data:

http://s17.postimg.org/xxwfd1usf/C_Pol_Element_98_MHz_Geo_File.jpg