A Cylindrical Polarimetric Phased Array Radar for Weather Measurement: Advantages and Drawbacks

While radar polarimetry was maturing to the stage that the national network of WSR-88D Doppler radars is being upgraded with dual-polarization capability, phased array radar technology started to receive wide-spread attention in the weather community given its potential for weather surveillance and for multi-mission tasks. Polarimetric radar provides multi-parameter measurements that reveal detailed microphysics of storms in addition to hydrometeor classification, accurate precipitation estimation, and the potential for improved storm forecasts. Therefore, the weather community and the nation expect that the future Multi-mission Phased Array Radar (MPAR) will retain all the capabilities of the polarimetric WSR-88D. It is advantageous to combine polarimetry and the agile beam Phased Array Radar (PAR) capabilities into one polarimetric PAR (PPAR) system. The planar PPAR (PPPAR), however, has significant deficiencies for polarimetric measurements, as well as other limitations such as increases in beamwidth, decreases of sensitivity, and a non orthogonal polarization basis if the beam scans off the array's broadside.

This paper suggests a cylindrical configuration for agile beam PPAR for weather surveillance. The Cylindrical Polarimetric Phased Array Radar (CPPAR) avoids the deficiencies that the PPPAR encounters. The CPPAR uses a sector of the cylindrical surface to form a beam with the broadside direction along the bisector of the illuminated sector. Using a CPPAR commutating scan in which the beam direction changes in azimuth by shifting the excitation of active elements column by column, the weights symmetry is maintained about the beam center. This way, the copolar and cross-polar antenna pattern and radar performance is scan invariant in azimuth, but the beam's orthogonal polarization basis is preserved in all directions. The CPPAR principle and potential performance are demonstrated through theoretical analysis and simulation. It is shown that the CPPAR has the advantage of a scan-invariant polarization basis, and thus avoids the inherent limitations of the PPPAR.