Multifunction Demonstration of the CASA Polarimetric, X-band, Phased-Array, Flat Panel Radar

Over the past nine years, the NSF Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) has been developing and deploying new technologies for better low-altitude weather observations based on dense networks of small X-band, polarimetric radars. While much of CASA's work has used mechanically scanned prototypes, electronically scanned phased array radars remain a key enabler to full realization of the CASA concept, due to their low maintenance costs, ease of installation on the sides of buildings and other existing infrastructure, and the flexibility of their instantaneous electronic beam positioning capabilities. In this paper, we present initial results from the first-ever low-cost phased array, polarimetric radar: the CASA X-Band Phase-Tilt Radar. This radar consists of three major subcomponents: a 1 square-meter aperture, dual-polarized, X-band, phase-tilt antenna; a low cost custom transceiver; and an embedded signal-processing computer. The phase-tilt antenna performs electronic beam steering in the azimuth direction while mechanically steering (tilting) in the elevation direction. The low-power electronics of the antenna combined with electronic steering in only one dimension reduces the manufacturing complexity and number of transmit/receive (T/R) elements for reduced cost. The flat panel form-factor of the antenna combined with low radiation hazard allows the radar to be installed directly onto existing infrastructure in urban areas. The low-cost transceiver provides adaptive beam positioning and waveform control in order to support rapid-updates of regions where meteorological and other objects are detected, while continuing to observe the surrounding area for changing conditions. The embedded signal processing computer calculates dual-polarized weather products in real-time, performing the coordinate transformations from phase-tilt to mechanically scanned geometry for downstream processing by standard commercial analysis software. The embedded computer also supports situational awareness by observing and monitoring nearby aircraft during system operation. After a brief description of the CASA X-Band Phase-Tilt Radar, test data will be presented to illustrate some of the radar's multifunction capabilities.