An experimental adaptive nulling receiver utilizing the sample matrix inversion algorithm with channel equalization

The authors explore two ideas for effectively achieving channel equalization within the framework of a narrowband sidelobe canceler. The first approach relies primarily on digital equalization to enhance conventional sample matrix inversion (SMI) performance, whereas the second utilizes feedback to extend the SMI method into the realm of analog adaptive cancellation. An experimental four-channel receiver that supports open-loop and closed-loop operation is described. As implemented, three different canceler modes are possible: feedforward, feedback, and a tandem feedback/feedforward combination. All three modes have been successfully demonstrated in bench experiments with a broadband noise source using the SMI algorithm. Cancellation ratios in excess of 50 dB have been achieved in a four-channel testbed system