3-Pol Polarimetric Weather Measurements With Agile-Beam Phased-Array Radars

Most actual polarimetric weather radars consider either alternate transmission of horizontal and vertical polarizations or simultaneous transmission of both polarizations. Simultaneous reception of vertical and horizontal components is always performed. The way these operating modes have to be modified, to cope with the loss of polarization purity and the increase of polarization channels coupling at some pointing directions when planar phased-array radars (PARs) are used, has already been discussed. Complete correction of these effects showed to be difficult, requiring precise control of the relative amplitudes and phases of the dipoles feeding signals on transmission in a pulse-to-pulse basis. If simultaneous transmission of vertical and horizontal polarizations is considered, complete correction has not been achieved. In this paper, the implementation of a third polarimetric measurement mode based on alternate transmission of three different polarizations with PARs is discussed. It is found that implementation of this method, which provides minimum-variance unbiased linear polarimetric covariance matrix estimates, with phased-array systems only requires simple adjustments at reception.