Optimized NLFM pulse compression waveforms for high-sensitivity radar observations

In order to provide adequate sensitivity in low-power radar systems, pulse compression has been used for decades in military applications, and more recently, weather radar. Due to the distributed nature and relatively low return power of hydrometeors, power efficiency of pulse compression waveforms is of great importance. The Advanced Radar Research Center at the University of Oklahoma has been developing novel waveform design techniques for weather radar platforms which provide excellent sidelobe performance while maintaining operational processing gains as high as 0.95 due to limited use of amplitude modulation. While directly applicable to weather observations, such waveforms are capable of lowering price points on all types of radar systems, ranging from military uses and aircraft detection to SAR applications. These waveforms have been implemented on the Advanced Radar Research Center's PX-1000 transportable, solid-state, polarimetric X-band weather radar, which operates at 100 Watts on each channel. Due to the very low peak transmit power, as well as a fully customizable waveform implementation and real-time signal processing architecture, PX-1000 serves as an excellent testbed for waveform research and development. An overview of the technical design method for optimized nonlinear waveforms is presented in detail, with comparisons to other popular nonlinear and heavily-windowed techniques. A description of implementation in a real system (PX-1000) is presented, including the need for, and implementation of, system-specific pre-distortion. A preliminary exploration of recent progress on Doppler tolerance correction for distributed weather targets is shown. Finally, data from the 20 May 2013 Moore, Oklahoma EF-5 tornado are shown, with a discussion of the technical implementation of optimized waveforms on PX-1000, including blind-range mitigation, multi-lag calculation of polarization moments, and the assumptions required for using current-generation pulse compression techniques in observations of extreme weather.