Abstract
In this paper, we propose a fast method for measuring the radar cross section of a complex target at non-normal incidences and Fresnel region antenna-to-target distances. The proposed method relies both on the physical optics approach and on averaging the field distribution over the transmitting and receiving antenna apertures. The ratio between the analytical expression of the radar cross section at far-field and Fresnel region results in a field-zone extrapolation factor. The RCS resulting from the scattering parameters measured at Fresnel region distances is then corrected with that field-zone extrapolation factor. The method is suitable to be used in a perturbed, multipath environment by applying the distance averaging technique, coupling subtraction or time gating. Our technique requires a very simple measuring configuration consisting of two horn antennas and a vector network analyzer. The experimental validation of the proposed technique demonstrates reasonable agreement with simulated radar cross section at non-normal incidence.
Highlights
Radar cross section (RCS) measurements are generally performed in anechoic chambers or in an open area test site (OATS), under far-field conditions
The far-field, radar cross section of a simplified model consisting of rectangular patches and slots can be computed analytically; it may serve as a reference for comparison purposes when extracting the RCS by processing Fresnel-zone data
We defined a field-zone extrapolation factor to be applied on the RCS figures measured in the Fresnel region
Summary
Radar cross section (RCS) measurements are generally performed in anechoic chambers or in an open area test site (OATS), under far-field conditions. Techniques for RCS evaluation from measurements at Fresnel region radar-to-target distances in a perturbed, multipath environment might be needed. The method fails when evaluating the RCS of flat targets, as the radius of curvature is infinite Physical optics overcomes this inconvenient by approximating the Stratton–Chu integral equation for the scattered field. The phase deviation between the contributions of different source points to the scattered field should be calculated, in order to find the RCS of a target using PO Such an evaluation is more difficult in the Fresnel region due to the reactive components of the field and the complexity of the surface integrals to be computed. We present a fast UWB technique for measuring the RCS of a complex target at non-normal incidences and Fresnel region antenna-to-target distances. A computing time saving technique with Fresnel integrals is developed and experimental results are eventually provided
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