Multi-Waveform Design for Enhanced Phased Array Isolation

The United States Federal Aviation Administration (FAA) and National Oceanic and Atmospheric Administration (NOAA) have partnered to explore the potential for a multifunction phased array radar (MPAR) that would subsume the surveillance responsibilities of a number of current national operational radar networks. Because MPAR will likely operate near-simultaneously from multiple planar faces (or sectors of a cylindrical PAR), self-isolation and spectrum usage are important research topics. This study describes novel design techniques for pulse compression waveforms that address these two challenges. Through the use of nonlinear frequency modulation optimization techniques, non-coherent phase offsets are incorporated into proven waveform design methodologies in order to provide increased isolation between waveforms. This technique provides the opportunity for better cross-polar isolation, resulting in lower polarimetric estimate biases. Additionally, applications to multi-sector or multi-face arrays such as MPAR allow for significant overlap in sector frequencies. This may reduce the overall spectral footprint of an MPAR network or provide opportunities for other uses of available spectrum, such as advanced fill pulse techniques, higher resolution, and cognitive transmit functions that utilize shared bandwidth. System-level validation of these waveform design techniques has been accomplished using the University of Oklahoma Advanced Radar Research Center's transportable, polarimetric, X-band PX-1000 radar platform. Simulations of both short and long pulses in a simultaneous transmit/receive two-sector polarimetric configuration are considered in order to quantify spectral usage impacts on a future MPAR system with completely autonomous missions in each sector.