Phase coding for the resolution of range ambiguities in Doppler weather radar

This paper deals with the recovery of Doppler velocities in the presence of overlaid echoes in range. Transmitted pulses are phase shifted to tag the echoes from scatterers separated by the unambiguous range. A new systematic phase code and an algorithm for estimating the mean velocities of 1st and 2nd trip signals when they are overlaid are presented. The return samples are phase corrected to cohere the 1st or the 2nd trip signal, leaving the other signal power spread in a deterministic manner across the spectrum. A new algorithm has been developed which enables one to recover the velocity of the weaker signal even when the overlaid power ratio is as large as 40 dB, for spectrum widths 4 m s/sup -1/ or less and an unambiguous velocity of 32 m s/sup -1/. Tests on simulated weather signals indicate that the method can be employed in a Doppler radar to effectively double the unambiguous range without the sacrifice of the unambiguous velocity interval.