Implementation of polarization diversity pulse-pair technique using airborne W-band radar

Abstract

Abstract. This work describes the implementation of polarization diversity on the\nNational Research Council Canada W-band Doppler radar and presents the\nfirst-ever airborne Doppler measurements derived via polarization diversity\npulse-pair processing. The polarization diversity pulse-pair measurements are\ninterleaved with standard pulse-pair measurements with staggered pulse repetition frequency, this allows a better understanding of the strengths and\ndrawbacks of polarization diversity, a methodology that has been recently\nproposed for wind-focused Doppler radar space missions. Polarization\ndiversity has the clear advantage of making possible Doppler observations of\nvery fast decorrelating media (as expected when deploying Doppler radars on\nfast-moving satellites) and of widening the Nyquist interval, thus enabling\nthe observation of very high Doppler velocities (up to more than\n100\u2009 m\u2009s−1 in\nthe present work). Crosstalk between the two polarizations, mainly caused by\ndepolarization at backscattering, deteriorated the quality of the observations\nby introducing ghost echoes in the power signals and by increasing the noise\nlevel in the Doppler measurements. In the different cases analyzed during the\nfield campaigns, the regions affected by crosstalk were generally associated\nwith highly depolarized surface returns and depolarization of backscatter\nfrom hydrometeors located at short ranges from the aircraft. The variance of\nthe Doppler velocity estimates can be well predicted from theory and were\nalso estimated directly from the observed correlation between the H -polarized\nand V -polarized successive pulses. The study represents a key milestone\ntowards the implementation of polarization diversity in Doppler space-borne\nradars.