Adaptive calibration of wideband digital beam formers with injection calibration

This paper presents a closed-loop internal adaptive calibration method for wideband digital beam formers in phased array applications. The channels are time aligned and calibrated before beam forming using an internal network for illumination and correction of the elemental electronic channels. This approach lowers the cost of wideband phased arrays by eliminating manual factory tuning. The internal calibration network enables calibration during operation without the implicit electromagnetic compatibility (EMC) concerns of a cooperative radiating source. The approach facilitates correcting for age related changes from the initial factory calibration, and for the inherent factory calibration residual errors. Measured data from an existing 22-phase center elemental digital beam former array was used to evaluate the method. The channel response was extracted and bit error rate (BER) was evaluated using a simulation test bench. The results show two orders of magnitude improvement in BER over a narrow band method based on singular value decomposition.