There have been numerous research efforts to create an equivalent lumped element model for microstrip antennas, even UWB antennas. What are the most commonly used ones?
Agilent Advanced Design System (ADS) is one of the software you can consider. You can export some exact lumped element models or certain outputs from software like CST and others and use them as functional components in ADS.
I have not used others so may not be giving you the best advice on them but Altium designer is also popular nowadays. I hope this is helpful.