Influences of ILS Localizer Signal over Complicated Terrain

This paper is concerned with a numerical simulation of Instrument Landing System (ILS) Localizer (LOC). LOC provides the guidance in the horizontal position of an aircraft for the runway center line. The radiation from LOC antenna generates the composite field which is amplitude modulated by a 90 Hz and a 150 Hz tone. The performance of the LOC is given by the difference in the depth of the modulation (DDM) along the runway centerline. However, their signals are influenced by the scattered waves if the LOC antenna is located over the complicated ground condition. In this paper, we consider the influences of the scattered waves caused by the complicated terrain, from a view point of the numerical simulation by the ray-tracing method (RTM). Firstly the basic principle of the LOC is introduced. Next, the simplified RTM is discussed. Finally, we show some numerical examples for field intensity distribution and DDM. We discuss how the scattered waves influence the performance of LOC.