Curvature has a great effect on fringing field of a microstrip antenna and consequently fringing field affects effective dielectric constant and then all antenna parameters. A new mathematical model for input impedance, return loss, voltage standing wave ratio and electric and magnetic fields is introduced in this paper. These parameters are given for TM01mode and using two different substrate materials RT/duroid-5880 PTFE. Experimental results are also introduced to validate the new model.