Then I studied all antenna parameters by increasing the height of the substrate of Structure A and keeping whole
remaining structure same as it was with h=0.8mm.
I kept h=0.05 , means h=2mm.
There is further improvement in BW and rad. efficiency, while all other parameters are same with negligible change as compared to the DR disc loaded antenna with h=0.8mm.
Here 15.92% (1.18 GHz) BW and 99.1% rad.
efficiency is achieved. RL plot for this structure is shown below: