Upper panel: reflected power S₁₁ for the feedhorn designed at INAF. Here, the simulation data are compared with the measurements. The effect of the adaptor used for the measurements is also shown, in lighter purple. Lower panel: INAF feedhorn test results for co-polar (Co) and cross-polar (Xp) beam pattern cuts: E-plane (E), H-plane (H) and 45°-plane. The results for the measurements (lines) versus the simulations (dashed) are shown near the band centre, 91.5 GHz. Our EM simulations confirm that the beam properties scale smoothly as a function of wavelength and, hence, we only show one representative frequency.