2D projection of the power beam pattern (θ is the zenith angle and ϕ the azimuth) showing the separation between the primary-lobe region Ω_PL (inner dashed circle) and the side-lobe region Ω_SL (grey ring) with a generic beam pattern pointing at zenith. The angle θ_1stnull,min (Eq. (4)) separates the two regions. The exceeding part of this asymmetric primary lobe is considered in the Ω_SL region. The black ellipse represents the primary lobe above −3 dB and the ellipse parameters FWHM and AR are defined in the inset box.