Electrical and Electronic Engineering, Imperial College London
Doi
Abstract
The objective of this thesis is to design computationally efficient DOA (direction-of-
arrival) estimation algorithms and beamformers robust to pointing errors, by
harnessing the antenna geometrical information and received signals. Initially,
two fast root-MUSIC-type DOA estimation algorithms are developed, which can
be applied in arbitrary arrays. Instead of computing all roots, the first proposed
iterative algorithm calculates the wanted roots only. The second IDFT-based
method obtains the DOAs by scanning a few circles in parallel and thus the
rooting is avoided. Both proposed algorithms, with less computational burden,
have the asymptotically similar performance to the extended root-MUSIC.
The second main contribution in this thesis is concerned with the matched
direction beamformer (MDB), without using the interference subspace. The manifold
vector of the desired signal is modeled as a vector lying in a known linear
subspace, but the associated linear combination vector is otherwise unknown due
to pointing errors. This vector can be found by computing the principal eigen-vector
of a certain rank-one matrix. Then a MDB is constructed which is robust
to both pointing errors and overestimation of the signal subspace dimension.
Finally, an interference cancellation beamformer robust to pointing errors
is considered. By means of vector space projections, much of the pointing error
can be eliminated. A one-step power estimation is derived by using the theory
of covariance fitting. Then an estimate-and-subtract interference canceller beamformer
is proposed, in which the power inversion problem is avoided and the
interferences can be cancelled completely
