Evaluation of a Near-Field Monostatic-to-Bistatic Equivalence Theorem

This paper presents the results of an investigation to quantitatively determine the limits of Falconer's monostatic-to-bistatic equivalence theorem (MBET). Falconer developed two extensions to Kell's MBET: one that is applicable to near-zone data and one that is valid in both the near- and far-zone regions. This paper encompassed collecting and analyzing both monostatic and bistatic radar cross-section data for perfect electrically conducting objects. Specifically, the authors analyzed the effects of varying the transmission frequency, scattering object complexity, and receiver bistatic angle. Objects ranged in geometric complexity from simple canonical objects to multifaceted shapes that produce multiple reflections. Empirical data collected in the far zone were compared with the analytical predictions produced by a commercially available method-of-moment (MoM) code. The code was run at X-band through K-band frequencies for a comparison with the measured data. The empirical bistatic data were then compared with the estimate produced by the MBET to ascertain the region in which the MBET approximation is applicable. Finally, the MoM code was used to produce near-field scattering predictions to facilitate the evaluation of Falconer's near-field MBET. It is shown that the complexity of the scatterer restricts the region of validity for the MBET, where shadowing and multipath interactions prevail. The disparity between the MBET accuracies for the different test objects used clearly illustrates this point.