: A circularly polarized （CP） two ports microstrip antenna simultaneously operated at two CP states is designed. The CP bandwidth of the antenna is increased from 0.35% to about 5%

but the antenna directivity due to the loss in the load is reduced by about 3dB. It is believed that such an advantageous trade-off for both will make this type of antenna much more usefulness

for example

in transmitting or receiving two CP waves of opposite senses simultaneously. The "crosstalk" between the two ports depends on the impurity of CP. It is about -19dB for axial ratio （AR） equal to 2dB

or -14dB for AR equal to 3dB. The method improving the isolation between two ports of antenna is also discussed.