Ambiguity Resolution Research In Pulse Doppler Weather Radars

Pulse Doppler weather radars can not only detect the location and intensity distribution of rain, but also detect the motion characteristics of hydrometeors according to Doppler information contained in weather echo which is helpful for acquisition of wind field information and the wind vertical velocity distribution. This is very important to the reasearch of the forming of precipitation, the analysis of the microscale weather system, and the forecasting of strong convection weather phenomenon.The dynamic range of weather targets echo power can exceed 100dB, and the mean velocity of moderate intensity storms are about 50m/s. Because of the relatively broad distribution of velocity in storms and the widespread distribution of rain showers, Pulse Doppler weather radars are plagued with the range-velocity ambiguity. In the Pulse Doppler radars, increasing the PRT increases(decreases) the unambiguous range while decreasing(increasing) the unambiguous velocity. Finding a solution to the problem of range-velocity ambiguity is a significant problem because ambiguities limit the inherent capability of the Pulse Doppler weather radars.The Batch mode is applied in American WSR-88D radar to mitigate ambiguity, which can seperate overlaid echoes in time domain. It's easy to realize. However this algorithm cannot recover the velocity from weaker trips and fails in regions where the overlaid trip powers in the short PRT scan are within 5dB of each other. Doppler velocity displays characterize these failures by encoding locations of such overlaid powers with a purple color.Over the last decade, two techniques have emerged as viable candidates to mitigate range-velocity ambiguity. These are SZ(8/64) phase coding and staggered PRT. In the phase coding technique, the transmitted pulses and the received echo samples are phase shifted to cohere the stronger signal and modulate the weaker...