A closed-form model for long- and short-range forward scatter radar signals from rectangular conductive targets

A closed-form model for the forward scatter radar (FSR) signal is presented with the goal to overcome the far-field (FF) limitation of the commonly used models. The proposed Fresnel closed-form (FCF) model, based on an approximation of the Helmholtz-Kirchhoff electromagnetic theory, correctly represents the received field of rectangular metallic targets crossing the baseline either in the short range or long range of the FSR transmitter and receiver. The FCF model outputs are validated by comparison with numerical results of a full-wave simulation tool in terms of received field amplitude and phase. The FCF model is exploited to assess the FSR detection performance loss, caused by the use of the FF models for some case studies of practical interest. Based on the proposed FCF model, we provide an analysis of the FSR ideal optimum performance achievable in these scenarios.