Accurate Planar Near-Field Results Without Full Anechoic Chamber
Authors: Greg Hindman, Stuart Gregson, Allen Newell
Planar near-field antenna measurements have largely been performed within fully absorber lined anechoic chambers. However, when measuring medium to high gain antennas, one can often obtain excellent results when testing within only a partially absorber lined chamber , or in some cases even when using absorber placed principally behind the acquisition plane.
As absorber can be bulky and costly, its usage often becomes a significant factor when planning a new facility. This situation becomes more difficult when the designated test environment is not exclusively devoted to antenna pattern testing with non-ideal absorber coverage being, in some cases, mandated, c.f. EMC testing. Planar test systems lend themselves to deployment within multipurpose installations as they are routinely constructed so as to be portable  thereby allowing partial or perhaps complete removal of the test system between measurement campaigns. Many of NSI’s large planar near-field system installations are implemented with only a partially lined chamber 
This paper will present measured data taken using a number of different planar antenna test systems with and without anechoic chambers to summarize what is achievable and to provide design guidelines for testing within non-ideal anechoic environments. NSI’s Planar Mathematical Absorber Reflection Suppression (MARS) technique [4, 5, 6] will be utilized to show additional improvements in performance that can be achieved through the use of modern sophisticated post processing.