A Multi-Beam on Receive Electronically Steerable Antenna comprising: a Tx array (2, 6) comprising a phased array of Tx antenna elements (3, 7) and having, in a Tx array plane, a geometric aperture with one or more pairs of parallel opposite sides; an Rx array (2, 4) comprising a phased array of Rx antenna elements (3, 5) and having, in an Rx array plane either coplanar with or parallel to the Tx array plane, a geometric aperture with one or more pairs of parallel opposite sides; the geometric aperture of the Tx array (2, 6) is rotated relative to the geometric aperture of the Rx array (2, 4) to such an extent that one or more pairs of parallel opposite sides of the geometric aperture of the Tx array (2, 6) are inclined or tilted relative to one or more pairs of parallel opposite sides of the geometric aperture of the Rx array (2, 4) by a non-zero angle other than, in particular lower than, 90°; the Multi-Beam on Receive Electronically Steerable Antenna further comprises an Antenna Controller designed to cause the Tx antenna elements (3, 7) to transmit an RF Tx beam having a Tx pattern with a wide Tx beamwidth, and the Rx antenna elements (3, 5) to simultaneously receive multiple RF beams processable to simultaneously synthesize multiple Rx beams having Rx patterns with Rx beamwidths individually narrower than the Tx beamwidth; the number of Tx antenna elements (3, 7) is lower than the number of Rx antenna elements (3, 5); the Tx beam has a lower directivity than the individual Rx beams so as to result in the Tx beam having a wider azimuthal and/or elevational beamwidth than the individual receive beams; and the Tx array (3, 7) has a gain lower than the Rx array (3, 5). a Tx array (2, 6) comprising a phased array of Tx antenna elements (3, 7) and having, in a Tx array plane, a geometric aperture with one or more pairs of parallel opposite sides; an Rx array (2, 4) comprising a phased array of Rx antenna elements (3, 5) and having, in an Rx array plane either coplanar with or parallel to the Tx array plane, a geometric aperture with one or more pairs of parallel opposite sides; the geometric aperture of the Tx array (2, 6) is rotated relative to the geometric aperture of the Rx array (2, 4) to such an extent that one or more pairs of parallel opposite sides of the geometric aperture of the Tx array (2, 6) are inclined or tilted relative to one or more pairs of parallel opposite sides of the geometric aperture of the Rx array (2, 4) by a non-zero angle other than, in particular lower than, 90°; the Multi-Beam on Receive Electronically Steerable Antenna further comprises an Antenna Controller designed to cause the Tx antenna elements (3, 7) to transmit an RF Tx beam having a Tx pattern with a wide Tx beamwidth, and the Rx antenna elements (3, 5) to simultaneously receive multiple RF beams processable to simultaneously synthesize multiple Rx beams having Rx patterns with Rx beamwidths individually narrower than the Tx beamwidth; the number of Tx antenna elements (3, 7) is lower than the number of Rx antenna elements (3, 5); the Tx beam has a lower directivity than the individual Rx beams so as to result in the Tx beam having a wider azimuthal and/or elevational beamwidth than the individual receive beams; and the Tx array (3, 7) has a gain lower than the Rx array (3, 5).