Improving weather radar observations using pulse-compression techniques

Pulse-compression techniques have been used for many years to increase sensitivity and range resolution in military and air traffic control radar systems. However, their application to ground-based weather radar has, so far, been very limited and restricted to research applications. This article describes the practical implementation of pulse compression using non-linear frequency modulation (NLFM) in a commercial digital processor/receiver and demonstrates its application to operational weather radars. Three case studies are presented, including the first application of pulse compression to ground-based travelling wave tube (TWT) weather radars. TWT radars use coherent transmitters with relatively low peak power compared to traditional magnetron or klystron systems, so in this case the sensitivity gain is crucial. The cases are from two different operational radars and illustrate the improved range resolution and sensitivity gain obtained using NLFM pulses compared to traditional simple pulses. Observations obtained using NLFM 40 mu s pulses were nearly 15 dB more sensitive than those recorded with lower resolution using 1 mu s simple pulses. A comparison of concurrent precipitation observations obtained with a TWT radar using pulse compression and low peak power (NLFM 40 mu s and 8 kW) and a nearby traditional magnetron weather radar (2 mu s and 250 kW) is also presented. The higher power system was more sensitive by less than 4 dB, but the improved resolution in the pulse compression allowed for enhanced Doppler filtering of ground clutter. Copyright (c) 2007 Royal Meteorological Society