I have simulated the structure both in CST and HFSS. they are quite the same, I didn't change anything (like mesh size, accuracy etc.) to bring them closer. Please take a look at the figures.
I know, you have document which shows different results. Would you please build such a structure to see whether the results given in the report is correct or not!
About coax feed transmission line: There is no power really going into the line from the coax (from S11 you can see it). For microstipline structure, it is better to use rectangular waveguide port at the end. You don't need to draw coaxial feed.