Circulator for Broadband Antenna

I need to transmit and receive a signal from the same broadband antenna which operates in frequencies of 500MHz-3GHz. I think a circulator is the best way to go about doing this, but I do not understand how or why. It is a microstrip antenna on FR4. Ideally, two of these antennas could communicate at all times in the entire specified frequency range.

It may be tough to find a circulator with that much bandwidth. Can you use a switch?

No, it needs to be able to access the entire bandwidth.