A status report on the RF and digital components of the multi-channel receiver development at the National Weather Radar Testbed

This paper describes the laboratory progress to add an eight channel receiver to the National Weather Radar Testbed (NWRT) system in Norman, Oklahoma. In particular, the hardware aspects of the RF down-conversion, RF switching, and digital receivers will be discussed. This will include a detailed discussion of the analog down-conversion sub-assembly and its design strategy. Laboratory based, test data from the system's multi-channel digital receiver will also be presented and discussed. Details about switching for the sum channel of RF waveguide will be presented, with its RS-232 contronller.

At the current time, a single-channel digital receiver is operational to mimic the current WSR-88D capability. The multi-channel digital data will foster a new generation of adaptive/fast scanning techniques and space-antenna interferometry measurements, which will then be used to improve numerical weather prediction via data assimilation. Differing from the conventional rotating radar, the phased array is suited for multi-mission capabilities so that a variety of targets may be observed simultaneously with a high degree of fidelity. The development of this new receiver system will be an enabling tool for related research for the next decade.

The multi-channel receiver will collect signals from the sum, azimuth-difference, elevation-difference, and five broad-beamed auxiliary channels. One of the major advantages of the NWRT is the capability to adaptively scan weather phenomena at a higher temporal resolution than is possible with the WSR-88D. Hemispherical coverage in 1 min or less vs. 4 min can be accomplished without comprising data accuracy. The multi-channel receiver will allow the direct implementation of interferometry techniques to measure crossbeam wind, shear and turbulence within a radar resolution volume. Access to the auxiliary channels will enable clutter mitigation and advanced array processing for high data quality with short dwell times. Potential benefits of high quality and high resolution data together with angular shear and turbulence include better understanding of storm dynamics and convective initiation, as well as better detection of small-scale phenomena including tornado and microbursts, ultimately leading to increased lead time for warnings, and improved weather prediction.

The project is a collaborative effort between the university and federal scientists. Assembly and testing of the instrument will be accomplished in the OU Atmospheric Radar Research Center (ARRC)'s Radar Innovation Laboratory (RIL) prior to integration into the NWRT. Scientists from the National Severe Storms Laboratory (NSSL) will take an active role in the integration of this instrument. The full conference paper will discuss this new project at OU in greater detail, which includes: advanced meteorological applications, predicted laboratory findings, initial designs and future risk mitigation strategies. Significant hardware integration should be completed in the fall of 2009, and a timeline for the subsequent work will also be discussed. This eight channel development is being supported by a grant from the National Science Foundation.