One embodiment discloses an antenna structure. An antenna structure comprises: a ground plane; a transmit balanced to unbalanced (BALUN) circuit comprising a first transmit connector coupled to a combined transmit port, and a second transmit connector coupled to the combined transit port; a receive BALUN circuit comprising a first receive connector coupled to a combined receive port, and a second receive connector coupled to the combined receive port; a transmit antenna element comprising a first transmit antenna sub-element coupled to the first transmit connector and a second transmit antenna sub-element coupled to the second transmit connector; a receive antenna element independent from the transmit antenna element and comprising a first receive antenna sub-element coupled to the first receive connector and a second receive antenna sub-element coupled to the second receive connector, wherein the transmit antenna element and the receive antenna element are orthogonally-polarized with respect to each other.