A radar antenna assembly configured to provide a panoramic field of view and configured to mount atop a vehicle as part of a radar system, said assembly including two antenna arrays (30, 32) within a single housing: a horizontal array including a horizontal substrate oriented substantially normal to a vertical axis, the vertical axis being perpendicular to a longitudinal axis and a lateral axis to substantially correspond to an upward direction and a downward direction relative to the vehicle, the longitudinal axis substantially corresponding to a forward direction and a rearward direction relative to the vehicle and the lateral axis being perpendicular to the longitudinal axis to correspond to a leftward direction and a rightward direction relative to the vehicle, wherein the horizontal substrate includes antenna elements each having a plurality of directive slots arrayed in a longitudinal direction parallel to the longitudinal axis and configured to detect objects in a forward area and a rearward area about the vehicle; and a vertical array including a vertical substrate oriented normal to the lateral axis wherein the vertical substrate includes other antenna elements each having a plurality of fan slots arrayed in a vertical direction parallel to the vertical axis and configured to detect objects in a leftward area and a rightward area about the vehicle (12, characterized by: the plurality of directive slots each having a lateral length measured in a lateral direction parallel to the lateral axis, wherein the lateral lengths vary progressively from a first lateral value of the lateral length of a first lateral slot located proximate to a first end of the antenna elements to a middle lateral value of the lateral length of a middle lateral slot located proximate to a mid-point of the antenna elements, and the plurality of fan slots each having an orientation angle of angular displacement relative to the longitudinal axis, such that the radar antenna assembly provides a field of view covering 360 degrees, and wherein the horizontal array and the vertical array cooperate to detect an object in a panoramic area that surrounds the vehicle. a horizontal array including a horizontal substrate oriented substantially normal to a vertical axis, the vertical axis being perpendicular to a longitudinal axis and a lateral axis to substantially correspond to an upward direction and a downward direction relative to the vehicle, the longitudinal axis substantially corresponding to a forward direction and a rearward direction relative to the vehicle and the lateral axis being perpendicular to the longitudinal axis to correspond to a leftward direction and a rightward direction relative to the vehicle, wherein the horizontal substrate includes antenna elements each having a plurality of directive slots arrayed in a longitudinal direction parallel to the longitudinal axis and configured to detect objects in a forward area and a rearward area about the vehicle; and a vertical array including a vertical substrate oriented normal to the lateral axis wherein the vertical substrate includes other antenna elements each having a plurality of fan slots arrayed in a vertical direction parallel to the vertical axis and configured to detect objects in a leftward area and a rightward area about the vehicle (12, characterized by: the plurality of directive slots each having a lateral length measured in a lateral direction parallel to the lateral axis, wherein the lateral lengths vary progressively from a first lateral value of the lateral length of a first lateral slot located proximate to a first end of the antenna elements to a middle lateral value of the lateral length of a middle lateral slot located proximate to a mid-point of the antenna elements, and the plurality of fan slots each having an orientation angle of angular displacement relative to the longitudinal axis, such that the radar antenna assembly provides a field of view covering 360 degrees, and wherein the horizontal array and the vertical array cooperate to detect an object in a panoramic area that surrounds the vehicle.