how to feed two arm archimedean spiral antenna for uwb application

Hi to all, i have designed two arm archimedean spiral antenna, but i have faced feeding problems, i have three feeding techniques: by using microstrip to parallel strip balun, coaxial calbe and discrete port. when i use the balun s11 is very poor, some they told me the balun is not connected to the arms of the antenna. for the coaxial cable s11 is good below -14dB for the entire frequency 3.1-10.6, but there is radiation and axial problems. and for the discrete port i simply connected to two arm of the antenna but i obtained very poor s11. therefore, i really need if any one can help me and guide me how can i feed this type of antenna. please any one who knows how to feed this antenna please help me
regard
abdi

Hi to all, i have solved the simulation problem by feeding the antenna by DISCRETE PORT, I got acceptable simulation results except for the axial ratio, please can any one, explain to me how to improve the axial ratio. thanks
regards
abdi