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 compa rison of its results with actual data recorded from operating ATC radars in S and L bands. Results obtained in an application on actual signals (relat ive 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 syst em specifically developed for this purpose. Due to the constitutive and operative characteristics of the systems, the r esults are affected by a low spectral resolution and a strong aliasing whic h give rise to problems in a correct analysis. The observed results have be en related to the physical phenomena generated by the structure of the comp lex target we suppose to be made of a rigid body and rotating parts which o riginate such a modulation on the echo signal that it is known in related l iterature as Jet Engine Modulation (JEM). These phenomena may be regarded as a signature of the particular couple "en gine-aircraft body" and in some flight conditions may offer significant hel p to a correct characterization of the aircrafts.