Abstract:
Estimating the direction of arrival is an important task in different applications
including radars, sonar and communications. Due to noise and interfering sources,
accurate parameter estimation is a difficult task. By using array of sensors, it is
possible to mitigate the noise problems. By combining the sensors’ outputs in an
efficient method, array processing results in an enhancement of the signal-to-noise
ratio much better than that of a single sensor’s output. Multiple sensors can be used for
estimating parameters of more than one signal. Using beamforming techniques, the
array can steer electronically rather than looking for different sources by mechanical
movement. Spatial filtering is carried out using beamforming to separate different
signals having same frequency but different spatial locations.
This thesis deals with different beamforming techniques for DOA estimation. High
resolution techniques such as Multiple Signal Classification (MUSIC) and Estimation
of Signal Parameters via Rotational Invariance Techniques (ESPRIT) which are
subspace based techniques are also discussed. Beamspace processing techniques which
give the advantages of reduced computational complexities plus enhanced resolution
are also discussed. For coherent signals, special techniques such as spatial smoothing
is used, the purpose of which is to decorrelate the signals. Finally, further resolution
improvement is achieved through the use of directional sensors.
