RFID tag with multiple port

Hi, guys!
Have somebody worked with UHF chip having two antenna connected to two different port? I obtained increment of read range about 1.4 times (near to theory ) using two orthogonal straight dipole, but using dipoles of different form led to essential decreasing of read range. I think there is problem with out-of-phase combining of signal from two antenna? Do somebody have any information about such case?

Hi aleksey0131.. Right now I am struggling with crossed dipole RFID tag antenna.. I dont have any idea how to calculte the reading range.. After I simulate the 2 ports antenna, I got two antenna impedances, which means each antenna have their own impedances.. I dont know whether I should take the averange of these two antenna impedances or should I combine those two impedances in order to calculate the reading range.. Please help me