Abstract: This invention relates to improvements in runway localizer antennas for the Instrument Landing System (ILS). The environment of modern airports has required that localizer antenna systems have larger apertures, with more elements, in order to produce the narrow beams needed to reduce multi-path interference. This, in turn, causes increases in the cost and complexity of the DU and associated coaxial feed cables. This invention uses features of a slotted cable antenna to replace a central distribution unit with a low-loss rigid copper transmission line running the entire length of the array. The radiating elements are fed from short cables through adjustable capacitors connected periodically along the rigid line.

Abstract: This invention provides an improvement in Glide Slope antenna systems of the earth-image type. The standard antenna usually is mounted on a steel tower located several hundred feet to one side of the runway, considered a safe distance to avoid being struck by an airplane. This invention, however, employs an antenna system using wide aperture slotted cable elements. Frangible construction permits it to be located safely much closer to the runway. The closer spacing, with the wide aperture, provides for a vertical guidance pattern that is narrower in azimuth, resulting in improved quality of guidance. An additional slotted cable, fed only with clearance signal, provides fly-up indication, both sides, over a wider azimuth sector.