Dual polarised crossed ring antenna array with high polarimetric purity

Polarisation purity becomes increasingly important in modern radio sciences. Accurate measurement of the state of polarization of the sources is crucial for pulsar timing and cosmic magnetism in radio astronomy. A polarization purity of-40 dB is expected ideally across the entire scan range as wide as ±60° from the zenith. With aperture array technologies for such applications, it is a demanding requirement. A crossed ring antenna array of a planar structure is proposed and a stable cross polarization over the wide scan angle is expected. The proposed antenna array is low profile and can operate in wide bandwidth. A finite array with 10×10 dual polarized elements has been manufactured and the radiation patterns of the 4×4 beamformed subarray and the centre elements in the finite array have been measured. The co-pol and cross-pol patterns both have been measured against a standard reference antenna, the intrinsic cross-polarization ratio is reported as it relates to the Jones matrix from the measurement quantities even after full calibration.