Pattern Synthesis and Digital Beamforming Capabilities of the Fully Digital Horus Radar

The Horus radar program has received support from the University of Oklahoma, the NOAA National Severe Storms Laboratory, and the US DoD Office of Naval Research. The current work reports results from the Horus-NOAA radar, which is operational. The radar comprises a mobile, fully digital, polarimetric, S-band Phased Array Radar (PAR) developed from its inception to meet demanding mission-critical observational requirements for next-generation weather surveillance. In this paper, we present antenna pattern synthesis methods that exploit the beamforming capabilities of Horus. The measured Horus embedded element patterns are utilized in the synthesis to account for practical antenna performance. We investigate phase-only and constrained-loss magnitude/phase pattern synthesis methods to shape the transmit beam in various ways, including intentional beam broadening ("spoiling") and beams with multiple simultaneous peaks in different directions. Results indicate that using synthesized beams with multiple simultaneous transmit peaks in different directions improves sidelobe isolation, producing two-way patterns similar to those from conventional single-beam operations. There is an inevitable loss in echo detectability (with respect to a full aperture pencil beam) due to the lower power density when spreading the mainlobe power. Evaluating these beamforming modes is critical for achieving high-temporal resolution polarimetric weather measurements with phased array radars.