An antenna system includes a right-hand circularly polarized antenna for receiving Global Navigation Satellite System (GNSS) signals and located on a receiver housing; a vertical semitransparent screen for providing an Down/Up ratio DU 9 ⁢ 0 = DU ⁡ ( θ e = 9 ⁢ 0 ∘ ) = F ⁡ ( - 9 ⁢ 0 ∘ ) F ⁡ ( 9 ⁢ 0 ∘ ) of −13 dB or better for at least some GNSS frequencies; the semitransparent screen being connected to a ground plane of the antenna; the ground plane being connected to a conductive receiver housing; the semitransparent screen further comprising a horizontal slot to which sets of lumped impedance elements are connected. Each set includes several lumped elements; where the lumped elements are capacitors and/or inductors and/or resistors; where the lumped elements in each set are connected in parallel or series; and the semitransparent screen including at least 4 segments arranged symmetrically around the center of the antenna and connected to each other.