Beamforming techniques are commonly used in array signal processing to find the ray-path-arrival directions. In general, beamforming is a spatial filtering process intended to highlight the propagation direction(s) of array-recorded signals. Below is a list of research projects related to beamforming techniques in our lab:
Delay-and-sum beamforming (DAS)
Delay-and-sum beamforming (DAS) is a simple linear beamforming method that relies on time delays to determine weights from a plane-wave signal model. DAS beamforming has been extensively used in underwater applications to determine the arrival angles. However, the performance of DAS beamforming is significantly degraded in shallow water environments due to the normal mode propagation. This research study investigates the performance of DAS beamforming when low-frequency signal propagates in a shallow water environment. [see the related poster]
Frequency-difference beamforming (FDB)
Conventional beamforming techniques may struggle when the receiving array is sparse (the receiving-array elements are many wavelengths apart). An unconventional beamforming technique (Frequency-difference beamforming) has been developed to overcome this limitation by manufacturing lower-frequency signal information from the higher-frequency broadband signal recordings.This method is applied to an experimental data set and results are presented here. FDB is compared with delay-and-sum beamforming here. For more information about the Frequency Difference Beamforming, please watch Dr. Abadi’s talk at Microsoft Research, Sept. 2014.
Frequency-sum beamforming (FSB)
When the environment between the source and the receivers is inhomogeneous, the recorded signal may be distorted and beamforming results may be increasingly degraded with increasing signal frequency. An unconventional beamforming technique (Frequency-sum beamforming) has been developed to alter this sensitivity to inhomogeneities by manufacturing higher frequency information from lower-frequency signal components via a quadratic (or higher) product of complex signal amplitudes. [see the related publication]