Mitigation of range/velocity ambiguities in the WSR-88D.

Over the past three years NSSL and NCAR have been investigating various methods to mitigate velocity and range ambiguities. A brief summary of the examined methods is first given and it is suggested that appropriate design of transmitted signal sequences and processing can improve the recovery of overlaid signals or increase the unambiguous velocity. At the onset of the study two well known promising schemes had been considered. These are the random phase coding and staggered PRT. During the course of this work a novel phase code that outperforms the random phase code has been discovered. It has emerged as a strong contender for application on the upgraded WSR-88D system. The staggered PRT technique, which heretofore was thought unsuitable because of its effect on ground clutter filtering, has been upgraded so that it can accomplish up to 40 dB of ground clutter canceling. Moreover this newly developed spectral processing of the staggered PRT sequence produces superior spectral moment estimates compared to the previous methods. Therefore it too is a candidate for the WSR-88D. Because the likelihood of range overlaid echoes decreases with the antenna elevation, it appears that a volume scan might include a suitable combination of both, phase coding methods (at lower elevation angles) and staggered PRTs (at higher elevation angles). Such possible volume scan pattern is proposed and tradeoffs therein are discussed.