X-Band Dual-Polarization Phased Array: Calibration and Performance

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The advent of phased array technology for meteorological applications has been realized recently with the development of research platforms such as the National Weather Radar Testbed and mobile Doppler phased array radars for rapid scanning such as the Rapid-DOW, MWR-05XP, and Atmospheric Imaging Radar. With these and initiatives such as the Multi-mission Phased Array Radar and the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), there is growing interest in the potential for use of phased array radars in weather surveillance and measurement. However, because the operational weather radar networks in the U.S. are now adopting dual polarization, it is anticipated that it will be necessary for future phased-array systems to support polarimetry for improved hydrometeor identification and rainfall estimation, with the same fidelity as is possible with today's reflector antennas.The Microwave Remote Sensing Laboratory in collaboration with the CASA Engineering Research Center, has recently developed a mobile, dual-polarization, solid-state, X-band active phased-array weather radar. With this award, experiments will be performed with this active phased-array radar to study its polarization performance, calibration and stability, biases, and other uncertainties particular to phased-array weather radar antennas. This array will be used in specific deployments and experiments of opportunity to gain experience in the practicalities of phased-array radar polarimetry.A combination of calibration experiments will be performed locally as well as deployments to the Great Plains. In particular, the radar will be deployed during two successive spring seasons to the Dallas/Fort Worth Urban Testbed, a quasi-operational/research radar network initiated by the CASA Engineering Research Center and primarily sponsored by the North Texas Council of Governments. Here, the phased-array radar will observe severe weather in tandem with other similarly sized, X-band, mechanically scanned dual-polarization radars. The intellectual merit of the research is experimental investigation of the impacts of polarization imperfections and projection errors and their compensation with a real dual-polarization phased-array radar, as well as characterization of the beam quality (sidelobes, precise matching of H- and V-polarized beams, cross-polarization) with a low-cost phased array. The performance will be benchmarked both via calibration targets and observations of weather with companion mechanically scanned antennas. The broader impacts of the research are improved understanding of the kinematics and dynamics of severe storms and their formation, ultimately leading to improved predictions of severe weather events. The incorporation of new technologies in weather observation will also inform users' interpretations and expectations of radar measurements for these purposes. In addition, the project includes strong involvement of graduate students from UMass working with investigators and users of the DFW Testbed. The phased-array radar will also serve as a teaching tool at UMass and at U. of Texas Arlington during deployments.