Low angle tracking using iterative multipath cancellation in sea surface environment

In low angle tracking, signal reflection from sea surface leads to severe errors in the target angle of arrival (AOA) estimation owing to the presence of both a target and its image in the mainlobe. In this paper, we propose a new scheme that iteratively suppresses the specular reflected signal to alleviate estimation errors. The iterative processing, which includes estimating the target angle, calculating the reflected image angle and updating the null position in beamforming, is performed to eliminate the image signal; thus, the measured target AOA including error converges to the true value. Moreover, by exploiting phase comparison method using separate aperture, there is no need to consider the distortion of the monopulse slope caused by mainbeam nulling. Design examples are presented to explicitly ascertain the accuracy of the proposed technique in estimating the true target angle.