Preserving the option for long term use of the instrument landing system (ILS)

摘要

Although the Global Psitioning System (GPS) appears to have an ever increasing role in the future of navigation, research continues to provide contemporary Instrument Landing System (ILS) options to meet the future needs for precision approach guidance. Developments in the areas of wide aperture antenna arrays to sustain or provide ILS service in multi-path environments are showing promising results. Implementation of a proven technique to reduce multi-path effects, which requires optimizaing the modulation phase of a two-frequency localizer system, has yet to be effected in the United States. Further benefits in minimizing multi-path effects could theoretically be gained by the use of a three-frequency localizer system. Application of some or all or these improvements would provide a basis to consider extended use of the ILS. With the belief that Category I, II, and III precision approach requirements of the future can be met, the complex issue of radio frequency spectrum (i.e. available channel frequency assignments) remains in the forefront as the limiting factor when long term use of the ILS is addressed.