Extended-range signal recovery using multi-PRI transmission for Doppler weather radars
November 1, 2005
Range-velocity (RV) ambiguity is a source of data quality degradation common to all weather radars. Various methods have been developed in recent years to combat this problem. For example, for the new NEXRAD Open Radar Data Acquisition (ORDA) system, the primary focus for range-overlay separation has been on phase-code transmission and processing techniques. There are, however, conditions under which the phase-code method fails to separate range-overlaid signals, e.g., when the overlaid power ratio is too high or the Doppler spectra are too wide. Phase-code processing also has no intrinsic capacity for velocity dealiasing. To address these issues, Lincoln Laboratory developed an alternative RV ambiguity mitigation scheme using multiple pulse-repetition interval (multi-PRI) transmission and processing. The range-dealiasing performance of the multi-PRI approach complements the capability of the phase-code technique. It can succeed when phase-code processing fails, and where it fails, phase-code processing succeeds (e.g., when an overlaid patch of signal is continuous and extensive in the radial direction). Multi-PRI also provides velocity dealiasing. However, because the multi-PRI algorithm was constructed for the Terminal Doppler Weather Radar (TDWR) with its primary mission of short-range coverage around airports, only the capability of first-trip protection was explicitly developed. This report extends the multi-PRI technique to the recovery of Doppler data from other trips, out to the long-range surveillance limit of NEXRAD. Simulated and real weather radar data are used to demonstrate the capabilities and limitations of the technique.