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V. Chandrasekar and R. Jeffrey Keeler

Abstract

Measuring the full polarization matrix using a research radar requires knowledge of the complex (i.e., amplitude and phase) antenna pattern to properly correct for bias errors in the measurements. However, generally only power patterns are available for analysis. Techniques are presented for obtaining bounds on the system differential reflectivity Z DR bias and the integrated cross-polarization ratio. A method for use of the phase shift between pulses to simultaneously estimate the differential phase and the radial velocity over the full Nyquist interval is described. NCAR's CP-2 10-cm antenna patterns with different horizontal and vertical polarization sidelobes were matched by rotating the feed support struts to be aligned on the diagonals so no preferential blockage occurred. The matched antenna patterns show much improved Z DR measurements in strong reflectivity gradients. The CP-2 3-cm antenna patterns were shown to be axially symmetric and typical of a well-designed, unblocked parabolic reflector.

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Frédéric Fabry and R. Jeffrey Keeler

Abstract

The design and implementation of signal-processing algorithms are specialized trades of radar meteorology practiced by a small group of experts and poorly understood by most other radar data users. Yet signal processing is the essential first step of radar data processing, and the skill with which it is done determines the type and quality of data that will be available to radar meteorologists. Like many other facets of radar meteorology, it is undergoing a rapid evolution as computing capabilities expand exponentially. In this chapter, an overview of the current state and evolution of signal processing for the nonspecialist is provided. To achieve this, the nature and the properties of the radar signal itself is first described, as it determines the type and quality of the information that can be obtained. After these foundations are laid, the current state of signal processing on operational radars and then some of the latest developments that may shape the future are described.

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