Non-ideal probe effect on the polarization extraction using the planar near-field phaseless antenna measurements

Abstract

The introduction of phaseless techniques has intrigued many researchers due to their promising cost effectiveness and their appropriateness for higher frequency operation, where there is a lack of network instruments. These techniques are not vulnerable to the phase instability and more importantly they are shown to reduce the probe positioning error effect. A number of interesting solutions for phaseless antenna measurements techniques are suggested in the literature, but most of these methods are not deeply investigated in terms of their performance in dealing with all kind of real measurement scenarios. This paper is focused on the planar phaseless measurements and specifically the polarization extraction issue. In a recent paper the polarization extraction issue is solved through the introduction of a single extra measurement along a direction different from the principal x- and y-directions [1]. The single extra measurements will basically extract the phase difference between the x- and y-directed fields at a single point in the measurement plane. As discussed in that paper an amplitude-only measurement along a different direction from x- and y-axis will resolve the phase difference and ultimately solve the polarization issue in a two-component manner. Due to the non-ideality of the probes in a real measurement the voltage amplitude induced at the end of the probe is not necessarily proportional to the electric field magnitude at that point. Moreover in general the probe voltage is a combination of both x- and y-directed electric field. Therefore the question that remains is weather one can use the measured voltages magnitude and still extract the polarization data and consequently the true co- and cross-polarized far-field patterns. Using the Kerns [2] well-known theory of plane-wave transmitting characteristic of the antenna, this paper will show that having the plane wave characteristic of the antenna one is able to compensate the probe effects in the planar phaseless measurement technique and come up with the correct polarization data.