32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/Fifth Conference on Coastal Atmospheric and Oceanic Prediction and Processes

Sunday, 10 August 2003
Phase Coding for Polarimetric Radar
J.C. Hubbert, NCAR, Boulder, CO; and V. Chandrasekar, R. J. Keeler, and N. Bharadwaj
Poster PDF (130.6 kB)
The fundamental range and velocity measurement limitation of pulsed radar systems is expressed by the following equation

ra va=cL/8

where ra, va are the unambiguous range and velocity, respectively, for wavelength L and where c is the speed of light.Since the product rava is a constant for a particular wavelength, increasing either one (ra or va) necessarily decreases the other. For L=10 cm (S-band) and a typical pulse repetition time (PRT) of 1ms, ra=150km and va=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 ra without compromising va.

To date phase coding has only been considered for single polarization radars. The advent of new high speed PC based radar receivers, with the ability of real time spectral processing, makes phase coding for dual polarization radars feasible. Issues surrounding phase coding for dual polarized radars are discussed and phase coding schemes are suggested. It is shown that is possible for radars with two transmitters to retrieve unaliasd velocities for weather targets while simultaneously having large unambiguous range.

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