Adaptive Wideband Digital Beamformer Calibration for Phased Array Antennas

Consumer and military users demand wider bandwidth systems to support a broad range of services from higher data-rate communications to anti jamming RADARs. Phased array technology, which improves spectrum management, can increase bandwidth to help meet user demand. A primary impediment to the adoption of this technology is cost [1].;Advances in direct radio frequency conversion and signal-processing fabric have fostered the emerging trend of elemental digital beamforming (DBF). Once the data are digitized at the elemental level, they may be used to form an arbitrary number of spatial beams. Similar to traditional phased array antenna systems, DBF arrays need highly accurate calibration. In contrast to traditional phased array systems, DBF arrays have access to the elemental data before beamforming. This offers the potential for in situ, i.e., automatic, adaptive calibration of the beamformer network [2].;In this dissertation, novel, adaptive wideband injection-based digital beamformer calibration techniques are examined with the goal of reducing the complexity of beamformer calibration in phased array antenna applications. The proposed adaptive calibration approaches can also improve system performance by correcting for age-related degradation and traditional residual calibration errors.;The research begins by formulating the problem of injection-based automatic calibration of digital beamformer networks in a mathematical framework. This framework is then used to explore the performance of both absolute and relative calibration network topologies. To minimize the complexity of the calibration network, classic narrowband methods are studied to find the breakpoints where the benefits of wideb and methods outweigh the complexity. To further reduce the complexity of implementing the proposed calibration approaches, various calibration illumination waveforms and analog to digital converter synchronization are also studied.;Through computer simulations, the performance of the calibration architectures are evaluated using bit error rate measurements. Several bandwidth use cases are explored to evaluate the effectiveness of both wideband and narrowband methods. In all cases, the simulation results demonstrate that studied techniques provide significant benefits to the performance of the array.