Direction Finding in the Presence of Mutual Coupling Direction Finding in the Presence of Mutual Coupling Direction Finding in the Presence of Mutual Coupling

The area of sensor array processing has attracted considerable interest in the signal processing community. The focus of this work has been on high resolution Direction Of Arrival (DOA) estimation algorithms that detect and locate aircrafts using radar systems. These algorithms exploit the fact that an electromagnetic wave that is received by an array of antenna elements reaches each element at di erent time instants. In practical antennas the elements of the array a ect each other through mutual coupling and this reduces the direction nding ability. The e ects of mutual coupling on direction nding are examined in this thesis. To be able to analyze the e ects of mutual coupling, the coupling needs to be calculated. Here, the coupling in a Uniform Linear Array (ULA) of thin and nite dipoles is calculated using basic electromagnetic concepts. The e ects of coupling on the estimation of the DOA is studied by calculating a lower bound on the variance of the DOA estimates, the Cram er-Rao lower Bound (CRB). It is found that a known coupling does not a ect the CRB signi cantly. Several methods of estimating the DOAs in the presence of a known coupling are derived and analyzed in simulations. However, in some cases the coupling might not be known, and one way of mitigating the e ects of an unknown coupling is to estimate the coupling along with the DOAs. The CRB for this case is derived. Several methods of estimating the directions and coupling parameters are also derived, and it is found that estimating the coupling along with the DOAs mitigates the e ects of an unknown coupling.