need help in CST MWS

hii
i am simulating dielectric resonator antenna in CST MWS and after that i am getting resonance frequency 2.6GHz and then i fabricate DRA and then take measurement on network anayzer then i get resonance frequency 2.73GHz and my theoretical resonance frequency is also 2.729GHz which is calculating by DRA dimensions and dielectric constant.so theoritical and exp. value matched but simulated can't.
so please tell me is CST provide wrong result or how can i improve S11 in the CST MWS?
help me..........

your calculation not accurate as simulation. so cst didn't get the exact results because there is a difference between the dielectric constant of the real resonator to this you put in the cst. Or the mesh you used for simulation not dense enough . Try adaptive mesh. Or try to solve it with Hfss sometimes the frequency solver give you better results.
pl