Design and implementation of an active calibration system for weather radars

Abstract

Weather radars permit meteorological quantities such as rainfall rate and wind velocity to be determined. These quantities are calculated from estimates of reflectivity, mean radial velocity and velocity spread. These estimates are derived from modified RF signal parameter measurements. RF scattering and propagation effects are the mechanisms which modify these parameters. Scattering is probabilistic in nature and therefore during measurement estimates of true conditions are formed. Errors in these initial estimations influence the accuracy of all subsequent quantities produced. For meteorological products to be as accurate as possible, the amount of uncertainty in each estimated quantity must be minimized. A well-controlled calibration process is used to reduce the influence of imprecisely known radar system parameters on the uncertainty of the formed estimates. This thesis presents the design and implementation of one such calibration system, an active, external calibrator for use with the MWR-05XP weather radar. Within this thesis, a background of the radar calibration problem, specific research objectives and related works are introduced and discussed. The theory behind the operation of weather radar is also presented and explained. The specific design is described in explicit detail and measured results provided in appendices. Conclusions on the success of the implementation are drawn with recommendations for future work.