Experimental Validation of the Multibeam Technique for Rapid-Scan, Meteorological Phased-Array Radar

Phased array radar (PAR) is under consideration as a replacement architecture for the next generation U.S. operational weather radar network (Stailey and Hondl, 2016). Studies have shown that by enabling volume scan rates of approximately one per minute, PAR can significantly improve the lead time and/or probability of detection for severe weather warnings (e.g., Yussouf and Stensrud (2010) and Wilson et al (2017)).

The volume scan rate for a meteorological radar is dependent on the coherent processing interval (CPI) necessary to achieve the desired variable estimate accuracy and the number of beam pointing angles to be serviced. If multiple pointing angles can be serviced during one CPI, the radar’s volume scan rate can be correspondingly increased. This paper describes an experimental assessment of the “Multi-Beam Technique (MBT)” (Zrnic et al., 2015) which utilizes concatenated pulse transmissions in multiple directions, followed by simultaneous reception and processing of the associated echoes using a highly-digital active array antenna. As described by Melnikov et al. (2015) a key challenge for MBT is suppression of unwanted mainlobe-sidelobe coupling

A 10-cm wavelength phased array radar at Lockheed Martin’s Moorestown, NJ facility has been configured to demonstrate MBT and quantify the inter-beam signal isolation that can be achieved using various methods. The planar, active array is configured to transmit concatenated pulses in two directions separated in angle by less than or equal to its subarray pattern width. Digitized subarray outputs are processed to form corresponding receive beams. As the beams are swept through the array’s field of view, returns from calibration targets, ground clutter and meteorological scatterers are analyzed to assess the amount of isolation between the two beams. Methods for reducing mainlobe-sidelobe coupling include frequency separation, orthogonal pulse waveforms (e.g. up- and down-swept non-linear FM) and the iterative cancellation method described by Melnikov et al. (2015).

This demonstration that multiple, simultaneously active beams can be used without increased sidelobe interference is critical in validating that meteorological PAR can achieve the desired rapid volume scanning without impacting the quality of its observations.

References:

2016. E. Stailey and K. D. Hondl, “Multifunction Phased Array Radar for aircraft and weather surveillance,” Proc. IEEE, vol. 104, no. 3, pp. 649-659, 2016.
2017. Yussouf and D. J. Stensrud, “Impact of phased-array radar observations over a short assimilation period: Observing system simulation experiments using an ensemble Kalman filter,” Mon. Wea. Rev., vol. 138, no. 2, pp. 517-537, 2010.
2018. A. Wilson, P. L. Heinselman, C. M. Kuster, D. M. Kingfield, and Z. Kang, “Forecaster performance and workload: Does radar update time matter?” Wea. Forecasting, vol. 32, no. 1, pp. 253-274, 2017.
2019. Zrnic, V. Melnikov, R. Doviak, and R. Palmer, “Scanning strategy for the Multifunction Phased-Array Radar to satisfy aviation and meteorological needs,” IEEE Geosci. Remote Sens. Lett., vol. 12, no. 6, pp. 1204-1208, 2015.
2020. Melnikov, R. Doviak, and D. Zrnic, “A method to increase the scanning rate of phased array weather radar,” IEEE Trans. Geosci. Remote Sens., vol. 53, no. 10, pp. 5634-5643, 2015.