Mitigation of range-velocity ambiguities for fast alternating horizontal and vertical transmit radar via phase coding

The data quality of weather radars is limited by range folding and velocity folding of echoes. Increasing the PRT (pulse repetition time) will extend the unabiguous range but decrease the unambiguious velocity. Shorting the PRT has the opposite effect. Systematic phase coding (SZ) of the transmitted pulses has been shown to be effective in mitigating the range-velocity ambiguity problem and has been deployed on the US Weather Service's NEXRAD network for single polarization (Sachidananda and Zrnic,1999). S-Pol uses fast alternating H and V polarization (FHV) pulses to achieve dual-polarization measurements, which complicates phase coding of the transmit H and V pulses. For example, second trip H-transmit echoes contaminate the crosspolar signal from the V-transmit signal. This paper examines the issues of phase coding for FHV radars and a phase coding algorithm is given. The algorithm is evaluated with both simulated data and experimental data from S-Pol (NCAR's S-band Dual-polarized radar).