Experiments of Diffraction Error on MLS Elevation Guidance.

In the diffraction region of a microwave landing system (MLS) elevation guidance. the field strength fluctuates due to such objects as buildings and hence the measuring error increases. This paper describes experiments to determine the effect of diffraction caused by the upper edges of a building. The results show that the field has a typical diffraction characteristic which can be calculated by regarding the building as a knife edge. It was found that the diffraction error cannot be ignored when measuring an angle, since the scanning beam is sharp in the vertical direction and flat in the horizontal direction. Hence, both the component proportional to the amplitude of the diffraction wave and that proportional to the partial differentiation of its incident angle (slope diffraction component) increase. It was found also that the measurement error characteristic around the shadow boundary, calculated by using the uniform geometrical theory of diffraction taking account of the slope diffraction, agrees well with the observational results. Generally, this method can be applied to the diffraction field strength and its measuring error estimation such as hangers. [ABSTRACT FROM AUTHOR]