UWB antenna for 4G application

Hi all,

I wanna design a UWB antenna (700-3800 MHz) for 4G application with polarization purity. I tried with Bow-tie antenna and achieved the bandwidth using assymmetrical legs but polarization purity is not there. And one more requirement is cosine pattern in elevation. Can anyone suggest me some other antenna which will have the above bandwidth, polarization purity and cosine pattern in elevation.

I used Reflector behind the bow-tie antenna to get the cosine pattern but refelector design for this broad bandwidth is possible?

How about a monocone antenna?