Wideband Beamspace Processing Using Orthogonal Modal Beamformers


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.

This is a preview of subscription content, log in to check access.

Figure 1
Figure 2
Figure 3
Figure 4


  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.


  1. 1.

    Coifman, R., Rokhlin, V., & Wanzura, S. (1993). The fast multipole method for the wave equation: A pedestrian prescription. IEEE Antennas Propagat. Magazine, 35(3), 7–12.

    Article  Google Scholar 

  2. 2.

    Colton, D., & Kress, R. (1998). Inverse acoustic and electromagnetic scattering theory (2nd ed.). New York: Springer.

    Google Scholar 

  3. 3.

    Marciano, Jr., J. S., & Vu, T. B. (2000). Reduced complexity MVDR broadband beamspace beamforming under frequency invariant constraint. In International symposium on antennas and propagation (pp. 902–905).

  4. 4.

    Lee, T. (1994). Efficient wideband source localization using beamforming invariancetechnique. IEEE Transactions on Signal Processing, 42(6), 1376–1387.

    Article  Google Scholar 

  5. 5.

    Agrawal, M., & Prasad, S. (1999). DOA estimation of wideband sources using a harmonic source model and uniform linear array. In IEEE Transactions on Signal Processing (pp. 619–629).

  6. 6.

    MacRobert, T. (1967). Spherical harmonics: An elementary treatise on harmonic functions with applications. London: Pergamon.

    Google Scholar 

  7. 7.

    Hoffman, M. W., & Buckley, K. M. (1988). Beamspace processing of broadband multiple beam antenna data for source localization. In Proc. twenty-second Asilomar conf. signals, systems and computers (pp. 813–817).

  8. 8.

    Oppenheim, A., Willsky, A., & Nawab, S. (1997). Signals and systems. Upper Saddle River: Prentice Hall.

    Google Scholar 

  9. 9.

    Kittredge, P. F., & Pulsone, N. B. (2000). Wideband angle estimation techniques for a beamspace application. In Sensor array and multichannel signal processing workshop (pp. 474–478).

  10. 10.

    Schmidt, R. (1986). Multiple emitter location and signal parameter estimation. IEEE Transactions on Antennas and Propagation, 34(3), 276–280.

    Article  Google Scholar 

  11. 11.

    Sekiguchi, T., & Karasawa, Y. (2000). Wideband beamspace adaptive array utilizing FIR fan filters formultibeam forming. IEEE Transactions on Signal Processing, 48(1), 277–284

    Article  Google Scholar 

  12. 12.

    Abhayapala, T. D., & Bhatta, H. (2003). Coherent broadband source localization by modal space processing. In 10th international conference on telecommunications (Vol. 2, pp. 1617–1623).

  13. 13.

    Abhayapala, T. D., Kennedy, R. A., & Williamson, R. C. (2000). Nearfield broadband array design using a radially invariant modal expansion. Journal of Acoustic Society of America, 107(1), 392–403

    Article  Google Scholar 

  14. 14.

    Van Trees, H., & Firm, K. (2002). Optimum array processing. New York: Wiley-Interscience.

    Google Scholar 

  15. 15.

    Wang, H., & Kaveh, M. (1985). Coherent signal-subspace processing for the detection and estimation of angles of arrival of multiple wide-band sources. IEEE Transactions on Acoustics, Speech and Signal Processing, 33(4), 823–831.

    Article  Google Scholar 

  16. 16.

    Ward, D., Ding, Z., & Kennedy, R. (1998). Broadband DOA estimation using frequency invariant beamforming. IEEE Transactions on Signal Processing, 46(5), 1463–1469.

    Article  Google Scholar 

  17. 17.

    Gabriel, W. F. (1988). Large aperture sparse array antenna systems of moderate bandwidth for multiple emitter location. In AP symposium (pp. 238–241).

  18. 18.

    Williams, M., Abhayapala, T., & Kennedy, R. (2007). Generalized broadband beamforming using a modal subspace decomposition. EURASIP Journal on Applied Signal Processing, 2007(1), 9.

    Google Scholar 

  19. 19.

    Xu, X. L., & Buckley, K. M. (1988). Reduced-dimension beam-space broad-band source localization: preprocessor design and evaluation. In Fourth annual ASSP workshop on spectrum estimation and modeling (pp. 22 –27).

Download references

Author information



Corresponding author

Correspondence to Thushara Dheemantha Abhayapala.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

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

Download citation


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