X-band Dual Polarization Phased-Array Radar for Meteorological Applications

This dissertation details the development and operation of a novel dual-polarized Phase-Tilt Weather Radar (PTWR) designed for meteorological applications. The use of radar has a well-documented history in detection and classification of weather phenomena, but due to the limited mechanical scanning speed, its usage for severe weather observations remains far from ideal. The PTWR utilizes phased-array technology and provides unique capabilities such as smart scanning, fast scan update, and tracking. This technology is considered a candidate for a replacement and consolidation of the current US weather and surveillance radar networks. The dissertation can be divided into three parts. First, the hardware design of the radar is presented. Methods of an element and array calibration are discussed. The measured sidelobe level and pattern match exhibit satisfactory performance. The algorithms for signal processing in alternate transmit alternate receive mode of operation are described in detail. The PTWR weather detection capability is validated by an inter-comparison with a collocated X-band high-power radar. These tests showed correlation exceeding 90% for measurements of reflectivity in a convective storm system. The results support the hypothesis that phased-array technology poses an attractive solution for weather remote sensing. The second part addresses the radar waveform considerations. The sensitivity of the radar can be improved by several decibels by means of pulse compression techniques. This is necessary, since the PTWR utilizes low-power solid-state transmitters. The work discusses the trade-offs in waveform design and introduces a novel compression filter, which outperforms traditional window-based solutions. The pulse compression performance is validated using clutter data collected by the PTWR, proving that a deep sidelobe reduction in excess of 40dB can be achieved at the minimal penalty in signal-to-noise level (below 0.5dB). Finally, the third part focuses on the scanning geometry of a 1-D phase-tilt ar- chitecture. It is shown that as the elevation angle is increased, the measurements are affected by a self-induced apparent canting angle. The methods of polarization rotation correction are presented. The biases in typical weather radar products such as reflectivity, differential reflectivity, correlation coefficient, and specific propagation phase, are investigated. The analysis shows that for elevation angles below 15deg , the retrievals errors are acceptable