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  • Core Business - Underwater Acoustics

Null-Steering Beamformer

This research project involved implementing a null-steering beamformer in the SAPPS / Scalable GSP architecture, and testing it on a number of synthetic test data sets prepared by FOI, the Swedish defence research agency. A null-steering beamformer allows the operator to remove the influence of one or more interferers or jammers by steering a null in the array gain pattern in the direction of the interfering source or sources. In testing, the algorithm proved to be effective and robust and it is anticipated that this method may be deployed in a future version of SAPPS for harbour surveillance applications.

In the image we have the original FOI test data conventionally-beamformed (without any steering of nulls.) This data set shows a marked interference pattern which is due to interference between the two visible tracks, each of which has the same signal waveform.
In the image 6NB_2ord.png, one of the two contacts was tracked using a broadband tracker and a second order null steered along this track, removing the influence from this direction of arrival. It is notable that the interference pattern is almost entirely suppressed and that additional contacts are now visible which were previously masked by the interference
Image Null Steering shows the user interface for the Null-Steering Beamformer in SAPPS.