radiation efficiency bigger than 1 cst

Hi all!
I've designed a microstrip p atch antenna with CST microwave.
I've noticed in the farfield computation,that the radiation efficiency is larger than 1?
Could someone please explain me how can it be,or where did I wrong?
I've attached my model.
Thanks in advance.

try to refine your mesh or give it more time
to run by chosing -40 or -50db in solver.

Yes,
in fact one of the possible reasons about the difference from the exact value (i.e. 1) of radiation efficency (or ratio Gain/Directivity) in a lossless structure is sometime related to abortion of a transient calculation at a too early stage.
In this case we have a meaning remaining energy inside the structure and that affects the correct evaluation of Gain (in fact the evaluation of this quantity is related also to the losses and a remaining energy is similar to a loss); then it is possible to have a radiation efficiency not equal to 1 also in a lossless structure.
Regards

Hi
I quickly calculated your structure down to -50 dB. (With MWS version 5)
The rad eff. is 0.9997. I guess we can count this as a 1 ...
F.

Hi,
I want to add my consideration about last RFSimulator post.
When you calculate your structure down to -30, -40, -50 or more dB, (in the case of lossless structure) you can see that directivity is almost stable; instead gain slowly tends to the directivity. Therefore also rad eff tends slowly to exact value (i.e. 1).
Regards