Adaptive beamforming using multimode feed horn antennas

The authors develop a new model for implementing adaptive nulling of interfering signals which is based solely on a single-feed horn antenna. The model uses a multimode feed antenna in which various modes are generated or extracted by means of slot coupling. Adaptive nulling is then carried out by treating each mode as an element of a phased-array antenna. The algorithm that is used to implement the adaptive nulling relies quite heavily on the QR decomposition method, a recursive least-squares algorithm which is amenable to systolic array processing. With proper choice of modes and design parameters for the feed horn antenna, simulation studies show that wide beamwidths (bandwidth), low sidelobe levels, and high signal-to-noise and interference ratio can be achieved with the proposed adaptive beamforming technique.<>