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antenna9071
Antenna-Theory.com Newbie

Joined: 17 Jun 2011
Posts: 8

 Posted: Fri Jun 17, 2011 9:33 pm    Post subject: recomendation of antenna type I want to build a antenna of this condition. what type of antenna is recomended? Patch antenna? *much metal in the environment *will sit on vehicle for hight speed max 200km/h *dual band 868Mhz( Rfid),2,45GHz *smal, max (w*L*H) 5cm*10cm*2cm *range max 15-20m *circular polarized
bigSteve
Antenna Wizard

Joined: 14 Mar 2009
Posts: 265

 Posted: Sat Jun 18, 2011 10:04 am    Post subject: Can you define much metal in the environment? If it is on a surface, then yes a patch antenna will work as the ground plane more or less will shield it from the metal below the surface. Or if it is a airplane for instance a monopole sticking out of the surface would also work. Sitting on a moving vehicle is a mechanical/aero concern, not an antenna concern, regardless of the speed. You don't have much volume there for 868 MHz, you might need a dielectric with permittivity of at least 4 to help get an efficient antenna in that volume. The max range is more of a receiver/transmitter issue, once that is defined you can determine the required antenna efficiency. You're probably not going to get good circular polarization so that requirement probably isn't going to happen......
antenna9071
Antenna-Theory.com Newbie

Joined: 17 Jun 2011
Posts: 8

Posted: Sun Jun 19, 2011 8:26 pm    Post subject:

 bigSteve wrote: Can you define much metal in the environment? If it is on a surface, then yes a patch antenna will work as the ground plane more or less will shield it from the metal below the surface. Or if it is a airplane for instance a monopole sticking out of the surface would also work. Sitting on a moving vehicle is a mechanical/aero concern, not an antenna concern, regardless of the speed. You don't have much volume there for 868 MHz, you might need a dielectric with permittivity of at least 4 to help get an efficient antenna in that volume. The max range is more of a receiver/transmitter issue, once that is defined you can determine the required antenna efficiency. You're probably not going to get good circular polarization so that requirement probably isn't going to happen......

patch antenna is the choise it looks like to be. you say

"You're probably not going to get good circular polarization so that requirement probably isn't going to happen......"

why?
bigSteve
Antenna Wizard

Joined: 14 Mar 2009
Posts: 265

 Posted: Mon Jun 20, 2011 2:12 am    Post subject: Tell me how you plan to get circular polarization
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