Determining Antenna Polarization Using Amplitude-Only Measurements With Linear-Polarized Antenna in Three Positions

Abstract

The paper proposes a novel procedure and the corresponding mathematical method to measure the polarization characteristics of a planar wave. The method is intended and described as a method for measurement of an antenna of unknown polarization using dipole-like linearly polarized antenna in far field zone of the measured antenna. The procedure consists of only three amplitude measurements using the linear-polarized antenna in three positions, followed by a specific mathematical transformation of the obtained values into polarization parameters – axial ratio and polarization ellipse main axis tilt angle. This mathematical transformation is one of the key contributions of the presented work. It is based on the decomposition of a wave into two circularly polarized waves and on the representation of the electric field as a vector whose components are complex numbers. Furthermore, the novelty of the proposed method is that only three measurements taken at arbitrary angles of the measuring antenna are sufficient to calculate the polarization ellipse parameters. This can have practical advantages, since this method does not require expensive phase measurements and lengthy phase calibrations. If beside axial ratio and polarization ellipse tilt angle also the sense of elliptical polarization is of interest, a simple supplement method is suggested. A potential impact of noise and interference presence during measurements on the applicability of the method in certain cases is thoroughly explained. A supplement method is needed in some of such cases which is explained in detail and the appropriate procedure given.

Keywords

• Antenna measurements
• antennas
• electromagnetic wave polarization
• polarization measurements
• circular polarization
• elliptical polarization