Multi-path Effects Phasor Phased Array Radar Low Altitude Target Angle Estimation And Tracking Technology

When phased array radar tracking low-angle target, the image of target caused by reflection from sea surface lead to multi-path effects. At this moment, both the direct signal and the reflected one impinge into the array, and make the amplitude and phase of the echo change, which cannot be separated from the direct one, thus cause server errors of elevation's estimation, even the failure of tracking.For the problem of multi-path effects, firstly the low-angle target tracking model of sea-surface is built up, and the geometric relationship among target, image and radar is analyzed. Later the characteristics of sea-surface reflected (including specular and diffuse) coefficients are investigated as well as the origin of multi-path effects.In succession, some angle measurement approaches have been investigated. And the results of them have been analyzed, from basic one to sum-difference beam measurements which are popular in phased array radar. Then there is a deep investigation on the application of sum-difference amplitude comparison in target tracking in the multi-path environment. Finally, the origin of multi-path effects is analyzed and some methods to eliminate the multi-path effects are introduced briefly.Then, the application of array signal processing to the DOA (direction of arrival) estimation of low angle target has been put emphasis upon. First of all, three de-correlation methods are introduced for the purpose of deducing the correlation between the direct signal and the reflected one. Then one of them is combined with classical MUSIC algorithm to do DOA estimation. Because of the low angle is often beyond the distinguishing range of MUSIC algorithm, to get better DOA estimation results, we make use of the well performance elevation distinguishing of the transform based covariance differencing algorithm, improve and apply it to DOA estimation , which can both reduce the correlation between signals and improve target's elevation distinguishing.Such approaches mentioned above cannot eliminate the multi-path effects totally. To get well tracking results, the IMM (interacting multi-path model) once used in maneuvering target has been adopt tracking to the tracking in multi-path. This algorithm...