(A) study on the low angle target tracking using iterative multipath cancellation in sea surface environment

Abstract

In low angle tracking, signal reflection from sea surface leads to the presence of both the targets and its image in the mainlobe of the radar. Then, the reflected signal causes severe errors in the target angle of arrival (AOA) estimation of the monopulse radar. In this thesis, 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. However, to apply the proposed method in estimating the low elevation target angle, the distortion of the monopulse pattern indued by mainbeam nulling should be considered. For the solutions, this thesis exploit two monopulse techniques:amplitude comparison monopulse with additional constraints and phase comparison monopulse. Simulation results are presented to explicitly ascertain the accuracy of tracking the true target angle with iterative cancellation. Those examples are also used to compare the performance of two monopulse methods which are applied to our proposed algorithm.