Novel Radar Observations By Exploiting Phased Array Radar: The Development of the Mobile C-Band Polarimetric Atmospheric Imaging Radar (PAIR)

Sponsored by the National Science Foundation’s (NSF) Major Research Instrumentation (MRI) program, the Advanced Radar Research Center (ARRC) at the University of Oklahoma has designed and developed the mobile C-band Polarimetric Atmospheric Imaging Radar (PAIR). In contrast to the conventional pencil beam operation for either reflector-antenna-based or phased array system, an imaging radar can “spoil” the transmit beam to illuminate a wide field of view, while multiple narrow receive beams can be formed simultaneously through the digital beamforming (DBF) techniques. As a result, the temporal resolution of the observations can be improved by the factor of the number of received beams formed (up to 10-20 times for the PAIR) in comparison to the pencil beam operation. In addition, those beams can better cover the observations in the vertical direction by minimizing any gaps (i.e., instantaneous RHI). It has been proposed to observe supercell, tornadoes, downbursts, hailstorms, lightning, etc.

Specifically, the operating frequency for PAIR ranges from 5.35-5.45 GHz (i.e., C-band). The selection of C-band has the benefit of less susceptible to attenuation. PAIR is a polarimetric phased array system and has 4,864 dual-polarization radiation elements. Each element has a peak power of 5 W per polarization with a maximum duty cycle of 20%. Different polarization modes including simultaneous transmission and simultaneous receiving, alternating transmission and simultaneous receiving, and circular polarization are available. PAIR can operate in either pencil beam mode with enhanced sensitivity or imaging mode to improve scan time. In the imaging mode, a spoiled beam will be used for transmission, where a user-defined beam shape can be obtained using phase-only beam synthesis optimization. Moreover, a total of 40-channel digitalized IQ signals per polarization will be generated for DBF. The two-way angular resolution is approximately 1.5 degrees in both azimuth and elevation directions. Both the pencil beam and spoiled transmitted beam can be steered electronically in the elevation direction. The azimuth coverage is achieved by mechanical rotation. As a result, a volume scan of 360 deg. in azimuth and 20 deg. in elevation can be achieved in 6-10 seconds. The scanning flexibility and fast update time have the potential to enable many scientific research areas, especially for those fast-evolving phenomena such as tornadoes, hail, downbursts, lightning, etc. In this presentation, the architecture and functionality of PAIR will be introduced. Moreover, some initial antenna measurements in the chamber and potential applications will be discussed. A photo of the fully assembled PAIR is provided in the left panel below, and the configuration of PAIR antennas is shown in the right panel.

link to picture: https://www.dropbox.com/s/63vx8xk6eogjqs0/PAIR.png?dl=0