On the RF Absorber Coverage of Antenna under Test Positioners

In any antenna measurement, the antenna under test (AUT) must be positioned in front of the range antenna. Positioners are typically made from metal or dielectrics. Regardless of the material, they will reflect and diffract the electromagnetic waves and influence the measurement. It is common to cover them in RF absorber. However, RF absorber is not perfect, and it will also influence the measurement. In this paper, several treatments of absorber on a roll over azimuth AUT positioner are analyzed. The range is a spherical near field range, with an open-ended waveguide (OEWG) illuminating the AUT. The analysis shows that sometimes a minimal absorber coverage is sufficient to get accurate measurements within a given uncertainty level.