Data quality improvements using SZ phase coding

The fundamental range and velocity measurement limitation of pulsed radar systems is expressed by the following equation

r_av_a=c L/8

where r_a, v_a are the unambiguous range and velocity, respectively, for wavelength L and where c is the speed of light. Since the product r_a v_a is a constant for a particular wavelength, increasing either one (r_a,v_a) necessarily decreases the other. For L =10cm (S-band) and a typical pulse repetition time (PRT) of 1ms, r_a=150km and v_a = 25m/s. Weather phenomena routinely exceed both of these limits. Phase coding of the transmit pulses for single polarization radars has been shown to be an effective method for the separation of range overlaid echoes thus extending r_a without compromising v_a. NCAR has been funded by the Radar Operations Center (ROC) of Norman, OK to investigate and implement phase coding for real time operation on NCAR's S-Pol. In 2004 NCAR in conjunction with NSSL delivered phase coding algorithms to the ROC for the implementation on the the NWS (National Weather Service) WSR-88D radars. Issues regarding the practical implementation of phase coding and possible improvements to the SZ algorithms are discussed. Examples of data quality improvement via SZ phase coding of experimental S-band radar data are given.