Experimental Investigation of Probe Immunity to Absorber Plate Position

Abstract

Dual-polarized probes with wide-bandwidth operational capabilities are highly desirable for time-efficient Planar Near-Field (PNF) measurements [1]–[2]. However, sometimes the performance tradeoffs necessary to achieve the desired operating bandwidth make such probes impractical for many applications. Traditional probes are often bandwidth limited, and their electrical size can be an undesired source of scattering in PNF measurements, especially if the probe-AUT distance is small. A novel octave-band probe has recently been presented combining wide bandwidth, near constant directivity, low cross-polarization, and minimum scattering [3]. Since the probes have a very broad pattern, an absorber collar must be placed behind the probe to prevent reflections from the metal flange, the coax adapter, and mounting structures behind the probe being received by the probe. In this paper the effect of the absorber plate on the measured antenna radiation pattern will be investigated by the use of the inverse source method [6]–[7] implemented in the software INSIGHT [8]. In particular, equivalent currents on the absorbers collar will be filtered in order to quantify their disturbing effect on the main radiation of the antenna aperture.