X-scan aircraft location systems

Abstract

Linear array antenna systems are used in X-scan aircraft location systems and methods able to avoid disabling azimuth error conditions caused by multipath reflections under roll and pitch conditions during aircraft carrier landing operations. Aircraft azimuth and elevation data is derived based upon time of incidence at an aircraft location of two transverse, diagonally oriented, scanned antenna beams. The aircraft location data is derived by comparing time of incidence data with data on known timing of scanning of the beams, which have diagonally-oriented fan beam patterns. A plurality of vertically oriented radiating elements are typically positioned along a line diagonal to the vertical to produce a diagonally oriented fan beam pattern. Beam scanning results from relative adjustment of signal portions supplied to the radiating elements. While beam scanning is nominally diagonal, the vertical radiation cut-off characteristics of the elements constrain vertical radiation and thereby enhance provision of a desired horizontally oriented approach window. A particular embodiment uses spaced feeds along a traveling-wave input waveguide, with coupling to radiating elements by interconnecting waveguide sections of successively longer length, to provide broad-band equalization of signal supply path lengths.