Wideband Beamspace Processing Using Orthogonal Modal Beamformers

Abstract

We introduce a novel beamspace processing structure that can be used for narrowband or wideband sources located either in nearfield or farfield of a sensor array. Main features of the new structure are: (i) a single parameter is used to steer the processor to any desired radial distance; (ii) a set of fixed frequency invariant orthogonal beamformers are used to transform array data into beamspace; and (iii) consequently, only a single set of beamspace weights are needed to process wideband beamspace data. The utility of the novel structure is illustrated by applications in interference cancellation and direction/range estimation.

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Notes

  1. 1.

    When the source and interferers have different spectra, it may be advantageous to use a separate set of beamspace weights in each frequency bin.

  2. 2.

    It is not our intention in this section to present results for specific iterative algorithms, we merely want to show indicative examples of how the proposed structure can be used in typical applications. Thus, we only present results from simulations using asymptotic data covariance matrices.

  3. 3.

    Any of a number of algorithms could be used with the proposed beamspace processor. See, for example, [14] for other suitable algorithms.

  4. 4.

    For example, the desired source could be speech and the interfere could be noise from an air conditioner which typically have a different spectral signature.

  5. 5.

    Observe that \({\tilde{M}}\) of these parameters are used to impose the distortionless constraint in Eq. 29, leaving \((P-1){\tilde{M}}\) parameters to reduce the interference.

  6. 6.

    Observe that one of these parameters is used to impose the constraint in Eq. 35, leaving (P − 1) parameters to reduce interference.

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Correspondence to Thushara Dheemantha Abhayapala.

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Abhayapala, T.D., Ward, D.B. Wideband Beamspace Processing Using Orthogonal Modal Beamformers. J Sign Process Syst 63, 277–286 (2011). https://doi.org/10.1007/s11265-009-0421-9

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Keywords

  • Broadband beamforming
  • Array processing
  • Adaptive arrays
  • Direction estimation
  • Interference cancellation
  • Nearfield
  • Sensor arrays