Digital array radar calibration and performance monitoring techniques for direct conversion and dual polarization architectures
Abstract
Recent years have seen a push toward low-cost phased array radar technologies with signal digitization moving closer to the antenna elements. Lowering the cost of the overall aperture precludes the use of brick-style T/R modules coupled to advanced, high-tolerance transceivers and instead calls for standard, surface-mount technologies with simpler transceiver architectures that have fewer frequency conversion stages. These changes are not without risk, as this leads to a number of non-idealities in the analog signal paths that place limitations on overall system performance and require more sophisticated calibration procedures. This is especially true of direct-conversion architectures, where in-phase and quadrature (I/Q) signal imbalances and mismatches in bandpass channel characteristics can lead to significant errors. At the same time, digitization of an increasing number of channels creates both processing and I/O bandwidth challenges that must be met with digital backend architectures that provide a maximum level of flexibility and capability without excessive hardware requirements. Proposed and demonstrated herein is a set of techniques that leverage the capabilities of a general hierarchical digital backend with digitization at the element level to overcome the limitations of these simpler analog receive chains while simultaneously providing new calibration and performance monitoring capabilities. These techniques, which feature direct, element-to-element mutual coupling measurements, are then extended and related to the real-world, practical challenge of calibrating dual-polarized phased arrays for weather radar applications, where precise knowledge and control of polarimetric antenna array patterns are required in order to meet strict performance requirements.
Degree
Ph.D.
Advisors
Chappell, Purdue University.
Subject Area
Electrical engineering
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