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Presenter: Iman Moazzen
Supervisor: Dr. Pan Agathoklis

Date: Fri, August 19, 2011
Time: 13:30:00 - 14:30:00
Place: EOW 430

ABSTRACT

Abstract:

There is considerable interest in wideband beamforming for applications in various areas such as radar, sonar, radio astronomy, and communications. Wideband beamforming techniques can be categorized into several classes. The first one called adaptive wideband beamforming is based on adaptive solutions of a constrained optimization problem in space-time. Some of the most common among them are Frost and the generalized sidelobe canceller algorithms. Another class of the beamformers is based on the frequency domain approach using Fourier transform. The third important class is based on multi-dimensional filtering. Another interesting approach for wideband beamforming is to use nested arrays. Such arrays are composed of several uniform linear arrays (each one is called subarray) with different apertures and distances between array elements arranged so that some array elements are superimposed.

In this presentation, a broadband beamforming technique using two-dimensional trapezoidal filters and nested arrays is proposed. Each subarray feeds into a subband beamformer processing an octave frequency band. Using subsampling in space and time all frequency subbands are transformed into the same frequency range in the frequency domain. This allows using the same trapezoidal filter design for all subbands. The advantage of using nested arrays is that the effective aperture for low temporal frequencies is larger than in the case of using a uniform linear array with the same number of array elements. This leads to a better spatial selectivity at low frequencies. The performance of the proposed beamformer is illustrated and evaluated using simulations.