Range oversampling techniques for polarimetric radars with dual transmitters

Range oversampling followed by a decorrelation transformation is a novel method for increasing the number of independent samples from which to estimate the Doppler spectrum, its moments, as well as several polarimetric variables on pulsed weather radars. Range oversampling techniques rely on the precise knowledge of the range correlation of oversampled signals, which is a function of the transmitter pulse envelope, the receiver filter impulse response, and the reflectivity field illuminated by the radar. Theoretical and simulation studies demonstrating the advantages of these techniques have been successfully verified on weather data collected with a single-transmitter dual-polarization radar. In contrast, recent experimental results on a dual-transmitter system have been rather negative; if the amplitude and/or phase mismatch between transmission pulses is disregarded in the formulation of the decorrelation transformation, processing of range oversampled dual-polarization signals with the standard whitening transformation can produce biased polarimetric variable estimates. This paper demonstrates that, by properly accounting for the amplitude and/or phase differences in the transmission channels, it is always possible to obtain unbiased polarimetric variable estimates. However, the accuracy of these estimators degrades as the degree of mismatch between the horizontally and the vertically polarized transmitted pulses increases.