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