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Caleb FultonIDEAS Microwave Laboratory, Purdue University
In recent years, there has been 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 typically precludes the use of brick-style T/R modules with high-tolerance components and transceivers and instead calls for standard, surface-mount PCB technologies with low-cost electronics. The increased role of digitization is a response to increasing demands on beamforming flexibility (degrees of freedom) and multi-functional operation. Using low-cost transceiver technologies and components is not without risk, as it can lead to a number of non-idealities in the analog transmit and receive chains that place limitations on signal and beamforming quality. At the same time, digitization of an increasing number of channels has created both processing and I/O bandwidth challenges that are being met with new digital backend architectures that provide a maximum level of flexibility and capability without excessive hardware requirements. Described 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 transceiver chains by providing new calibration, performance monitoring, and digital beamforming techniques. These techniques, demonstrated using the Army DAR (Digital Array Radar) testbed, feature direct, element-to-element mutual coupling methods through a distributed direct-conversion transceiver architecture. The calibration challenge is then extended to dual-polarized weather radar radar applications, where these performance-monitoring and initial calibration routines may provide a means by which the inherent polarization errors in planar phased arrays can be mitigated to enable high-quality polarimetric measurements.
Wednesday, 13 July 2011, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Small Seminar (Rm1001)