The Polarization property of the planeWaveExcitation function can be used to set the incident wave's magnitude in the units of V/m. For an incident wave power of 1uW the calculation has to be done to convert it to V/m and then specify it in the Polarization property.
h = planeWaveExcitaion('Polarization',[0.02 0.02 0.02]);
cur = feedCurrent(h,75e6);
Hope this helps!
