Dielectric resonator bandwidth is pretty narrow. From this forum and some little experience i learned that the best way of designing DRO is to
1) design stable amplifier for frequency F. There must be input and output microstrip lines.
2) couple dielectric resonator to input and output lines (put between lines, just google for any parallel feedback DRO pictures or photos)
Many old papers just use RLC resonator to simulate DR. There are formulas for computing R,L,C for DR parameters. Also this method gives correct phase shift through resonator.
I think you can simulate DRO in some 3D EM simulator. But it is not obvious to me how correctly set all dielectric parameters and shapes to get realistic result. It seems not very easy without experience.
At 4GHz, which is less than 5GHz (mass production wifi and cellular technology) , measuring equipment is relatively cheap. Vector network analyzer can help understand and learn many things.