Calculation of Radar Reflecting Properties of Jet Engine Intakes Using a Waveguide Model

In the RCS analysis of jet aircraft, the engine intake and exhaust ducts present special problems which have not been widely discussed in the literature. In this paper an idealized example of a subsonic type of intake duct is chosen as an example for analysis. The idealization of the intake consists of a terminated circular waveguide, the termination being designed to represent the first stages of the jet engine. Examples of theoretical RCS and glint pztterns predicted with this model are given, showing the phenomenon of compressor modulation and the effects obtained with changes in wavelength and receiver-transmitter geometry.