Radar signals analysis and modellization in the presence of JEM application to civilian ATC radars

This paper describes the application of a simulation software and the comparison of its results with actual data recorded from operating ATC radars in S and L bands. Results obtained in an application on actual signals (relative to commercial aircraft echoes) collected from observations on the echo received at an ATC radar system are presented. These signals were recorded along many field experiments carried out by the authors on a recording system specifically developed for this purpose. Due to the constitutive and operative characteristics of the systems, the results are affected by a low spectral resolution and a strong aliasing which give rise to problems in a correct analysis. The observed results have been related to the physical phenomena generated by the structure of the complex target we suppose to be made of a rigid body and rotating parts which originate such a modulation on the echo signal that it is known in related literature as Jet Engine Modulation (JEM). These phenomena may be regarded as a signature of the particular couple "engine-aircraft body" and in some flight conditions may offer significant help to a correct characterization of the aircrafts.