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Nearfield broadband array design using a radially invariant modal expansion

Summary: Nearfield broadband array design using a radially invariant
modal expansion
Thushara D. Abhayapala and Rodney A. Kennedy
Telecommunications Engineering Group, Research School of Information Sciences and Engineering,
Australian National University, Canberra ACT 0200, Australia
Robert C. Williamson
Department of Engineering, Faculty of Engineering and Information Technology, Australian National
University, Canberra ACT 0200, Australia
Received 22 December 1997; revised 5 February 1999; accepted 29 September 1999
This paper introduces an efficient parameterization for the nearfield broadband beamforming
problem with a single parameter to focus the beamformer to a desired operating radius and another
set of parameters to control the actual broadband beampattern shape. The parameterization is based
on an orthogonal basis set of elementary beampatterns by which an arbitrary beampattern can be
constructed. A set of elementary beamformers are then designed for each elementary beampattern
and the desired beamformer is constructed by summing the elementary beamformers with frequency
and source-array distance dependent weights. An important consequence of our result is that the
beamformer can be factored into three levels of filtering: i beampattern independent elementary
beamformers; ii beampattern shape dependent filters; and iii radial focusing filters where a single
parameter can be adjusted to focus the array to a desired radial distance from the array origin. As
an illustration the method is applied to the problem of producing a practical array design that


Source: Abhayapala, Thushara D. - Department of Information Engineering, Australian National University


Collections: Computer Technologies and Information Sciences