Plane Wave Analysis and Evaluation of an Indoor Far Field Conductive Chamber

Martin Marietta designed and brought on-line an indoor far field chamber used for radar cross section (RCS) evaluation. The 40\u27 x 40\u27 x 70\u27 range has conductive walls on all sides except for the pyramidal absorber covered back wall. The chamber was designed such that wall/floor/ceiling interactions occur with a distance (time) delay allowing for their isolation from the test region. Software gating techniques were used to remove these unwanted signals. Additionally, optimal feed horn gain and beamwidth were investigated to achieve maximum quiet zone size and purity. This document presents an analysis of the conductive chamber using Geometrical Optics (GO). The objective was to analyze and evaluate the plane wave quality in the chamber test region. The conductive walls allowed the use of ray tracing to determine stray scattering signals in the quiet zone. Signal paths were traced until they reached the absorber lined back wall where they were considered terminated. The evaluation of the plane wave was performed using the angle transform technique. This new method involved measuring the complex RCS vs. aspect angle of a rotating cylinder. The component plane wave information was integrated in the angle domain and transformed to the spatial domain. The quiet zone size and purity were determined from field probe data. The measured results were compared to analytical results and measured antenna patterns