[CST MWS] ""farfield is inaccurate" means .

i simulated the simple dipole and examined the farfield.
But, with the farfield pattern picture, there is warning.
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"warning : farfield is inaccurate"
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anybody know this meaning? now i attach the very picture.

that's because the simulation boundary is to close to the dipole with respect to the wavelength. it is better to use the open + add space boundary when simulating antennas in free space. cst will set a proper simulation boundary for you
best regards

thank you, mr. kleinsmurf69!
But, as you can check my picture, i want to see the radiaton of dipole [which is loacated at the boundary between uppper air layer and lower substrate (my case is lossless GaAS)].
So, to give a infinite concept to all directions (=no reflected wave from any boundary) , i attached the all sideplanes to open boundary plane.
So, if i would use the open (add), that is out of my original intention.
could examine my structre closer. plz.
thank you again your comment!

if you do not want to use the open(add) function (all it does is pads the volume with λ/8 free space on all sides, by default), then you could make the substrate bigger - it also implies that your substrate is large (approx. infinite) in comparison to the dipole. of course it will take more time, but at least it will give you a useful result. maye uploading a pic with the boundary conditions will help.