Radar cross section computation of aircraft with engine inlets including fan blades

A combination of asymptotic and rigorous methods is used to compute the radar cross section of an aircraft with engine inlets that include fan blades. The engine inlet and the blades are solved rigorously with an integral-equation method while the aircraft is analyzed with an asymptotic method. A three-step process is proposed that is both accurate and fast.

I. Introduction

At radar frequencies, 1 GHz and above, asymptotic methods are usually preferred to calculate the radar cross section (RCS) of aircraft. Such methods include Ray-Launching Geometrical Optics [1], which is closely related to Shooting and Bouncing Rays [2], and Physical Optics [3], [4]. These methods can, in principle, be applied to open-ended cavities, but for a realistic engine inlet with fan blades, a rigorous method is required, e.g. the Multi-Level Fast Multipole Method (MLFMM) [5]. The challenge then becomes how to combine rigorous and asymptotic methods to compute the RCS of an aircraft with engine inlet. While extensive literature exists on RCS analysis of open-ended cavities [4]–[8], publications on RCS of entire aircraft with realistic engine inlets are scarce or nonexistent. This paper proposes a three-step process that obtains fast yet accurate results using the commercial electromagnetic simulation tool FEKO [6], which incorporates hybrid rigorous methods and asymptotic methods.