Estimation: Direction of Signal Arrival

Estimation problems in theoretical as well as applied statistics have long been of great research interest given their importance in a great variety of applications [1]. In signal processing literature, direction of arrival (DOA) denotes the direction from which a propagating wave arrives at a point, where usually a sensor array is located. The goals of array processing are to explore the spatial and temporal cross-correlations between the array outputs so as (1) to enhance the signal-to-noise ratio beyond that of a single sensor’s output (2) to characterize the field by determining the number of sources of propagating energy, the locations of these sources and the waveform they are emitting (3) to track the energy sources as they move in space. Relevance Often there is the associated technique of beamforming. Beamforming takes advantage of interference to change the directionality of the array. Under the narrowband signal assumption, the delays between each individual sensor can be expressed as signal phase differences. The underlying idea is that if a propagating signal is present in an array’s aperture, the sensor outputs, delayed by appropriate amounts and added together, reinforce the signal with respect to noise or signals propagating in different directions. Compared to the conventional delay-and-sum beamforming technique, most modern approaches to signal processin