Polar plot does not have x-y. The simulation results shows two planes: one is the xy and the other is xz (yz omiited). The actual 3D radiation pattern is donut shape. Thus depending on the cut you will see different polar radiaiton pattern.
along the polarization direction the farfield is zero. In the perpendiuclar plane it is circle.
The angle showing in the above plots is phi, from 0 to 360 deg.
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