Validation of Near-Field Monostatic to Bistatic Equivalence Theorem Sarah J. Gabig, Kelce Wilson, Peter J. Collins Andrew J. Terzuoli, Jr. Air Force Institute of Technology P. 0. Box 3402 Dayton, Ohio USA 45401-3402 Tel: + 1937 255 2024 Fax: +1937 656 4055 ABSTRACT The purpose of this research is to quantitatively (determine the limits of Falconer’s Monostatic to Bistatic Equivalence Theorem (MBET). Falconer developed two extensions to Kell’s MBET, one applicable to near zone data and one valid in the far zone region. This work encompassed collecting and analyzing both monostatic and bistatic radar cross section (RCS) data for perfect electric conducting (PEC) objects. Specifically, this research analyzes the effects of varying the parameters of transmission frequency, object shape complexity, and receiver bistatic angle. Objects range in geometric complexity from canonical objects comprised of simple scatterers to multifaceted composites that sustain numerous interactions. Empirical data collected in the far zone are cornpared to analytical predictions produced by commercially available electromagnetic computer codes, both a method of moments (MOM) code and a near-field Physical Optics co’de. The codes ran at X-band through K-band frequencies for a comparison with object data. Further, the empirical bistatic data are compared to the estimate produced by the MBET, to ascertain the region in which the MBET approximation is applicable. Finally, electromagnetic computer codes are used to produce near-field scattering predictions to facilitate validation of Falconer’s near-field MBET. INTRODUCTION Monostatic radars that employ duplexers illuminate and view scattering from objects with a single antenna, while bistatic and multistatic systems can transmit and receive signals from multiple antennae. Bistatic measurement geometry incorporates physically separated transmit and receive antennae whose relation to the test article is described through the bistatic angle p. This work analyzes the bistatic scattering from a representative PEC object comprised of simple canonical shapes, i.e. corner reflectors, open and closed cylinders, and a shadowing plate. Far-field bistatic scattering predictions generated with two commercially available electromagnetic scattering codes are evaluated against the empirical data for their accuracy. Finally, Falconer’s Monostatic-to-bistatic scattering conversion formulae for far-field and near-field [ 1, U.S. Government work not protected by U.S. copyright 1012 Giuseppe Nesti, Joaquim Fortuny European Microwave Signature Laboratory EC Joint Research Centre 1-21020 Ispra (VA), Italy Tel: +39 0332 78 5922 Fax: +39 0332 78 5772 m Object A Object B Fig. 1: Test objects (adapted from [3]) 21 are evaluated for their ability to predict bistatic scattering phenomena. DEVELOPMENT This paper presents a five phased research prqject as follows: 1) collection of far-field empirical data, 2) validation of Falconer’s far-field MBET with the empirical data, 3) validation of computer prediction codes with empirical data, 4) generation of near-field scattering with computer codes, 5) validation of Falconer’s near-field MBET with computer generated scattering data. Objects A and B, shown in Fig. 1, were chosen for their ability to highlight various scattering phenomena at different look angles, such as traveling waves, creeping waves, multi-bounce, and shadowing effects. Co- polarized (VV, HH) monostatic aind bistatic waterline pattern cut and imaging data was collected according to the matrix in Table 1 at the European Microwave Signature Laboratory (EMSL) of the EC Joint Research Centre in Ispra, Italy. Table 1 : Bistatic RCS Measurement -20 - 225