Cross-Polar Canceller (XPC): A Technique to Reduce Cross-Polar Pattern Contamination in Polarimetric Weather Observations

This paper proposes a novel technique to improve cross-polar isolation for polarimetric phased array antennas used for meteorological observations, referred to as cross-polar canceller (XPC). It is based on the use of canceller antenna elements transmitting a scaled version of the original waveform in the polarization where the cross-polar contamination is observed but with opposite phase. The technique involves calculating the correct number of canceller elements, their location in the array, and a scaling factor for the amplitude and phase of the selected canceller elements such that maximum cross-polar isolation is possible. It is intended for dual-polarization, fully digital, phased array radar systems. It can also be applied to sub-array architectures if amplitude and phase control is possible at the element level. Previous similar efforts illustrated the potential of this technique for the alternating transmission/reception of horizontally and vertically polarized waves. In this paper, we present progress towards using this technique for the simultaneous transmission/reception of horizontally and vertically polarized waves. Preliminary results show that this technique is capable to improve cross-polar isolation by 15 dB on average, at the cost of ~0.32 dB loss in copolar pattern gain per canceller element used. The XPC technique is being implemented in the Horus system, an S-band, polarimetric, fully digital phased array system developed by the Advanced Radar Research Center (ARRC) at the University of Oklahoma (OU).