Design and Evaluation of Multibeam Transmit and Nulled-Receive Array Patterns for Polarimetric Weather Radar Surveillance

Abstract

Simultaneous transmit beams offer a direct way to increase temporal sampling of phased-array weather radar while retaining narrow angular illumination. With $N_{b}$ directions observed in one dwell, the number of dwells required to sample a fixed angular set can be reduced by a factor proportional to $N_{b}$ . Herein, we design and experimentally evaluate an end-to-end multibeam transmit/receive scan mode on the Horus fully digital polarimetric phased-array radar. Measured phase-only transmit patterns containing two through seven simultaneous mainlobes are paired with one precomputed constrained receive beam per mainlobe. The receive coefficients use established regularized linearly constrained minimum-norm synthesis to suppress returns from the other known transmit directions. An end-to-end scan mode is proposed, and scans with two through seven peaks are demonstrated. Polarimetric measurements of the patterns are used to quantify two-way performance. Relative to conventional digital beamforming (DBF), the measured nulled-receive beams reduce average copolar crosstalk integrated sidelobe level (ISL) by 13.6–18.9 dB over 3-dB mainlobe regions and by 9.9–13.8 dB over 10-dB mainlobe regions. The case-average receive white-noise-gain loss is 0.03–0.49 dB, with a worst-beam loss of 0.59 dB. Average intended-beam integrated cross-polar levels remain between −40.0 and −37.8 dB (as with conventional DBF), and the average H/V centroid separation remains below 0.084°. These results establish a concept of operations for rotating, polarimetric phased-array radar, capable of meeting temporal resolution, spatial sampling, and data quality requirements simultaneously.